615 Ameys Track, Foster VIC 3960. Vacant block measuring approx 1231m2 in delightful Coopers Rd. Easy walk into town but enjoying a rural feel with an open northerly aspect and views over the countryside. Gently undulating, established trees. 115 Boolarra-Foster Rd, Foster VIC 3960. January 7th, 2016. Rural North East is bounded by Baw Baw Shire and the locality of Mirboo North in the north, Latrobe City and Wellington Shire in the east, the localities of Toora North and Mount Best, the Franklin River, the locality of Wonga, Boolarra-Foster Road, the localities of Foster, Foster North, Stony Creek and Meeniyan in the south, and the.
Road routes in Victoria assist drivers navigating roads throughout the state, as roads may change names several times between destinations, or have a second local name in addition to a primary name. There are two main route numbering schemes with numeric and alphanumeric routes. The original route numbering scheme, now known as the Metropolitan Route Numbering Scheme and restricted to the Melbourne metropolitan area, consists of numbered National Highways, National Routes, and State Routes, each identified with a different shield-shaped route marker. The Statewide Route Numbering Scheme, introduced in the 1990s, has replaced the previous scheme outside Melbourne, and some routes within Melbourne. It consists of alphanumeric routes, which are a one-to-three digit number prefixed with a letter – M, A, B, or C – that denotes the grade and importance of the road.[1]
M routes[edit]
M roads provide consistently high quality road conditions and are always divided dual or more carriageways. M roads are the primary transport links between Melbourne and other capital cities or provincial centres.[2]
A routes[edit]
A roads serve the same purpose and provide the same high quality road conditions as M roads, the only difference being that A roads are single carriageways. A roads also carry less traffic than M roads.[2]
B routes[edit]
B roads are sealed roads wide enough to accommodate two lanes of traffic with good line markings, provide adequate shoulders and high quality and visibility signage. B roads are the primary transport links for regions not connected by either M or A roads, as well as major tourist routes, such as the Great Ocean Road (B100).[2]
C routes[edit]
C roads are generally sealed two lane roads with shoulders and serve as links between population centres and the major road network. For example, the Mount Dandenong Tourist Road is route number C415.[2]
C101 to C198[edit]
C203 to C298[edit]
C305 to C392[edit]
C401 to C498[edit]
C505 to C620[edit]
C701 to C805[edit]
See also[edit]References[edit]
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1 Regional Guide to Vi&orian Geology Edited byj, McAndrew and M.A,H.Marsden
2 Regional Guide to Victorian Geology Edited by John MCAndrew Division of Mineralogy, CS I R 0 and Marcus A.H.Marsden School of Geology, University of Melbourne. School of Geology, University of Melbourne 1973 Second Edition
3 First published 1968 Second edition 1973 Wholly set up in Australia by the editors. Cover design by Stuart Crluth, Technology Section, Education University of Melbourne. Printed, collated and bound in Australia by Hollyoak Manufacturing Company, Melbourne, for the School of Geology, University of Melbourne. This book is copyright. Apart from any fair dealing for the purpose of private study, research criticism, or review, as perrnitted under the Copyright Act, no part may be reproduced in any manner whatsoever without the written perrnission of theeditors. W,_ John McAndrew and Marcus A, H. Marsden 1968, School of Geology, University of Melbourne, Publication No. I. Registered in Australia for transrnission by post as a book. ISBN O X Available from the University of Melbourne Parkville, Victoria 3052, Australia. School of Geolo8Y» ii
4 PREFACE This volume was originally prepared as the handbook for the nineteen geology excursions forming part of the 39th Congress of the Australian and New Zealand Association for the Advancement of Science, held at Melbourne in January, It provided an overall review of the geology of Victoria, and a new account of the geology of important areas other than the Grampians for which an excellent description had been published as Memoir Z5 of the Geological Survey of Victoria. The first edition of the 'Regional Guide to Victorian Geology' was a revised version of the handbook. Continuing demand has led us to rearrange and revise the Regional Guide, as well as to enlarge it by the addition of a new chapter on the geology of the Melbourne district. In addition to the acknowledgements recorded in the preface to the original Excursions Handbook we are pleased to acknowledge the continued support of the School of Geology, University of Melbourne, and the Commonwealth Scientific and Industrial Research Organisation. The School of Metallurgy of the University of Melbourne and the Geological Survey of Victoria cooperated in the preparation of the Second Edition. We also acknowledge with thanks the valuable assistance received from Mesdames L. Holding, R. Howe and J.E. Richardson, Misses T. Sapountiz and N. Stewart, and Messrs D. Campbell and G. Ouick. The illustrations from early publications of the Geological Survey of Victoria are reproduced with kind permission of the Director. The photograph on p. viii is of portion of the relief model of Australia prepared in the School of Geology, University of Melbourne, under the direction of Professor E. S. Hills. John McAndrew M. A. H. Marsden University of Melbourne April, iii
5 PREFACE TO ORIGINAL HANDBCOK This Handbook has been prepared as a guide to the Section C excursions held during the 39th Congress of ANZAAS at Melbourne in January, It provides a new account of the geology of the excursion areas and thus of most of the geologically important areas in Victoria The Handbook has been made possible through donations towards the cost of publication by a number of companies and we acknowledge with thanks the generosity of Aberfoyle Tin N. L. Mount Morgan Ltd. Anaconda Aust. Inc. North Broken Hill Ltd. Anglo American Corporation (Australia) Ltd. Peko-Wallsend Investments Ltd. Australian Selection (Pty.) Ltd. Sydney Smelting Co. Pty. Ltd. Broken Hill South Ltd. The Broken Hill Proprietary Co. Ltd. Consolidated Gold Fields (Australia) Pty. Ltd. The Electrolytic Refining and Smelting Conzinc Riotinto of Australia Ltd. Company of Australia Ltd. Esso Exploration Australia Inc. United States Metals Refining Company. Electrolytic Zinc Company of Australasia Ltd. United Uranium N. L. International Nickel (Australasia) Pty. Ltd. Utah Development Co. Kennecott Exploration (Australia) Pty. Ltd. We stern Mining Corporation Ltd.. The Mount Lyell Mining and Railway Co. Ltd. We also acknowledge the support afforded individual authors by their employing organisations, the Bureau of Mineral Resources, Commonwealth Scientific and Industrial Research Organization, Geological Survey of Victoria, State Electricity Commission, The Broken Hill Proprietary Co. Ltd., and the University of Melbourne, in the preparation of their contributions. The coloured geological map of Victoria has been donated by the Department of Mines of Victoria. Through kind permission of the Australasian Institute of Mining and Metallurgy, the 'introductory paper has been reproduced, with modifications, from 'Geology of Australian Ore Deposits', Second Edition, The Royal Society of Victoria has kindly permitted reproduction of figures from its Proceedings. This volume has been prepared with the unstinted and able assistance of a number of persons which is gratefully acknowledged, in particular Miss H. Hawkins, who typed nearly all the copy, Mesdames E.A. Marsden, M.E.M. McAndrew, and F.M. Tattam, Misses P. Carolan and E. Spry, Messrs. F. Canavan, A.C. Frostick and D.J. Taylor, and Dr. J.J. Jenkin. J. McAndrew O. P. Singleton M. A. H. Marsden Chairman, Section C Editors 8 January, 1967 iv
6 To many, 'conservation' applies to animals and plants or the environment around them, but how many readers regard the geological features of the environment as worthy of conservation? A moments reflection will show that geological features are more vulnerable, as once despoiled they are not regenerated as are living organisms. In some overseas countries, notably Britain and the United States many geological features such as fossil and mineral localities have been ruined by overzealous collectors, and public access to many such sites is now restricted. Localities have been overwhelmed by hammer-bearing groups of students and club members, and literally hacked to pieces and carried away by persons with no thought for the future. With a few outstanding exceptions this situation has not yet arisen in Victoria. However an increasing number of important geological sites have in recent years been seriously degraded. Because of the upsurge of interest in geology more people are visiting and examining the classical geological areas of Victoria for which this book serves as a guide. If you are a teacher or excursion leader please ensure that your students do not hammer or dig outcrops irresponsibly or collect specimens which will be later thrown away. Remember that since many fossils are scarce and often scientifically valuable they should be shown to a professional palaeontologist at the Geological Survey, the National Museum or one of the Universities. Likewise, many minerals, particularly well-crystallized specimens, are rare, and should be shown to a professional petrologist or mineralogist. In this way you may contribute something to the science of geology, as many have in the past. I appeal to all who use this book whether teacher, student, professional or amateur to ensure that Victorian geological sites and areas remain unspoiled for the enjoyment and education of those who will come after us. Thomas A. Darragh, Convenor, Geological Conservation Sub-committee, Victorian Division, Geological Society of Australia. V
7
8 Swan Hill I 2I5rang. O Echuca Albury S epparton 0 9 orryong Wangarratta 1 Bena1la 'y 3 Mi ta Ben i o Tawa a ` Hea hcote 9 0 S Ymour.Mansfi _ ld om lo Lancefield eo woodend Ei1d n Mc.Howicc wllimilton Bagghus Ma;- h8 3 ` 4 Tabberabbera ' chan 2 I-lealesville Port Campbel / e,mortlake E 0 RN Maffrao 1 Lake E a * D d,sa e 12 7 G Ong an enong EQ J O rn n W rrn 001 Colac orqua Yal uin ` Leongat Q aff _ 1 AP l1 Bay 4 LocA'r1oN or THE REGIONS DESCRIBED Waratah Bay Chapter numbers shown
9 REGIONAL GUIDE TO VICTORIAN GEOLOGY CONTENTS Preface._._._. Photograph of relief model _ Geological map of Victoria f21ci1'1g 1. Outline of the geology and physiography of Victoria O. P, Singleton 2. Geology of the Melbourne district A. H. M. VandenBerg, with contributions by M. A. H. Marsden and J. McA_ndrew 3. Quaternary sediments of the Maribyrnong River, Keilor _ 4. Devonian rocks of Lilydale _ 5. The Dandenong Ranges Igneous Complex _ 6. Geology of the Mornington Peninsula 7. Geology of the Geelong district 8. Geology of the Bacchus Marsh district _ Editorial _ E- D- Gill C0I1' 1 ib ~1ti0I1 P. Singleton _ V.A. Gostin O. D- SPSIICSI'-J0neS _. _ O. P. Singleton 9. Stratigraphy and structure of the Palaeozoic of west-central Victoria J. A. Talent and D, E. _Thomas 10. The Castlemaine-Chewton Goldfield F. 11. Geology and petrology of the Macedon district _ C. Beavis and J. McA.ndrew _ O. P. Singleton 12. Geomorphology of the Western District volcanic plains. lakesand coastline C. D. Ollier and E. B. Joyce 13. Mesozoic and Tertiary stratigraphy of the Otway region _ 14. Geology of South Gippsland. _. O. 15. The brown coals of the Latrobe Valley C.. O. P. Singleton P. Singleton S. Gloe 16. Late Cainozoic geology and geomorphology of south-east Gippsland J. J. Jenkin 17. Geology of East Gippsland. _. _. _ J.A.. Talent 18. Palaeozoic evolution of east-central Victoria M.A.. H. Marsden 19. Palaeozoic metamorphism and igneous activity of north-east Victoria M. D. Leggo and F. C. Beavis 20. The Riverine Plain in northern Victoria J. M. Bowler and P. G. Macumber iii viii vii
10 CHAPTER l 1 OUTLINE OF THE GEOLOGY AND PHYSIOGRAPHY OF VICTORIA1 1 v by O. P. Singleton INTRODUCTION. Victoria, of 87, 884 sq. miles, lies astride the Palaeozoic mobile belt of eastern Australia towards its southern end. Nowhere is the Precambrian basement exposed. Its Palaeozoic geological history was one of tectonic instability induced by primary forces directed from an easterly direction, which initiated deep depositional troughs. Progressive stabilization from the late Ordovician onwards deformed the sedimentary filling along generally meridional trends and was finally completed during the Carboniferous. A different, milder tectonic regime, producing an east-west orientation of the younger rocks, was established during the Mesozoic and has persisted to the present day as witnessed by Quaternary movements and the continued existence of Bass Strait and the highlands of Victoria. Rocks of known Cambrian age outcrop as the cores of a number of narrow, predominantly meridional belts whose boundaries are normally high-angle reverse faults. These and other 'axes' played a fundamental tectonic role through the Palaeozoic as structures which were persistently but intermittently anticlinal in nature (Fig. 1). The internal structure of the axes is very complex in marked contrast to the simple though intense structures developed in the surrounding rocks. Granitic rocks of at least six definite ages occur. Certain groups of intrusives, for example, the muscovite granites of north-we stern Victoria, can be recognized, but the age of only a few can be reliably estimated. Many other granitic bodies, particularly in the east and west of the State, are of unknown age. Individual dyke suites such as the Wood's Point swarm have been accurately dated but there are many others whose age are quite unknown, some being associated with mineralization. CAMBRIAN. Lower Cambrian volcanics During early Cambrian time a thick sequence of basic lavas, in part at least submarine, was extruded accompanied by pyroclastics, lenticular cherts, and minor intrusives (Thomas and Singleton, 1956). Originally a suite of olivine-poor basalts and augite andesites, these greenstones have undergone low-grade dynamic metamorphism and metasomatism, and are now spilitic (Tattam, personal communication). Feldspars have been universally albitized, pyroxenes frequently replaced by chlorite and,or actinolite, and secondary minerals such as epidote, clinozoisite, and stilpnomelane developed. Locally bodies of serpentine rock have been formed. Associated minor feldspathic intrusions include diorites and albite porphyrites, with small bodies of albitized micro-granite at Heathcote. At Heathcote small intrusions of pyroxenite have been converted to talc rock containing small veins of magnesite. Middle and Upper Cambrian sediments. The greenstones are followed by Middle to Upper Cambrian sediments characteristically without detrital quartz and granitic' accessory minerals. At Heathcote the laminated neritic Knowsley East Shales include beds of sandstone and at least one band of conglomerate, all derived from the greenstones. Besides a 'dendroid' fauna, there are two Middle Cambrian trilobite assemblages which, being only 100 ft. apart, indicate some condensation in sedimentation. At Lancefield contemporaneous dark pyritic shales also contain 'dendroids'. In both areas the younger Cambrian is represented by some 2000 ft. of the unfossiliferous Goldie Shales which at Lancefield pass conformably up into the Ordovician. At the Dolodrook River, inte rbedded with tuffaceous rocks, is the condensed Dolodrook Limestone with trilobite-brachiopod assemblages spanning several zones of the late Middle and early Upper Cambrian. North-we st of this, at the Howqua River and Tatong on the same Mt. Wellington Axis, cherts and dark shales separate the greenstones and Ordovician sediments. 1Modified from GEOLOGY OF AUSTRALIAN ORE DEPOSITS', Second Edition, 1965, pp (Eighth Commonwealth Mining and Metallurgical Congress, Melbourne).
11 2 Elsewhere faulting brings the greenstones into juxtaposition with post-cambrian rocks. The lack of Cambrian outcrops outside the axes is unfortunate because, from internal evidence alone, the existence of geosynclinal conditions in central Victoria during the Cambrian cannot be demonstrated conclusively. In western Victoria there is contrasting evidence of an earlier influx of normal terrigenous detritus from a crystalline terrain, shown at Mt. Stavely, south-east of the Grampians, by interbedding of low-rank greywacke and shales with tuffaceous rocks of the presumed Cambrian greenstone suite. GRDOVICIAN. By the Ordovician, g_eosynclinal conditions were firmly established throughout the State. In central Victoria a flood of quartzose detritus entered at the beginning of the Ordovician, building up a very thick monotonous alternation of low- rank greywackes, shales and slates deposited under anaerobic bathyal conditions. Individual lenticular greywacke beds, overall fine to medium grained and characteristically graded, are interbedded with dark shales frequently containing sedimentary pyrite., True black graptolite shales are normally absent. Hills and Thomas (1954) have shown the greywackes to be turbidity current deposits, with the dark shales accumulating during intervening quiescent periods. The greywackes contain some chert grains, soda feldspar, muscovite and accessories such as zircon and tourmaline. Volcanicity was completely absent. Although benthonic forms are virtually absent, the very rich and almost complete sequence of Ordovician graptolite faunas in central Victoria makes possible one of the most detailed zonal subdivisions in the world (Table 1). TABLE l. Faunal stages and correlation of the Ordovician (Harris and Thomas, 1938). Early Yapeenian Middle Darriwilian Late Bolindian Ordovician Castlemainian Ordovician Ordovician Eastonian (Tremadocian- Chewtonian (Llanvirnian- (Caradocian- Gisbornian Arenigian) Bendigonian Llandeilian) Ashgillian) Lancefieldian Although.extremely uniform and monotonous, the sequence varies in both thickness and lithology. Hills and Thomas (1954) estimated 12, OOO ft. of Lower to Middle Ordovician at Bendigo and 12, O00 ft. of Lower to Upper Ordovician at Lancefield, but conspicuously less on the Mornington Peninsula. Individual zones may also vary greatly in thickness. In slowly deposited sequences, chert bands become conspicuous. The relative proportions of lithologies vary in different parts of the sequence. The Lancefieldian contains thick greywacke sequences and only rare intercalations of shale; the Darriwilian contains a high proportion of shale. Such variations, and the consequent behaviour of the rocks during deformation,' have had a considerable influence on the structural control of quartz reefs, and at times on the localization of gold. Regional developments of the Ordovician. Between the Heathcote Axis and a line from Ballarat to Wedderburn, the sequence is predominantly Lancefieldian to Darriwilian. It is known in considerable detail (Thomas, 1939), the major structures having been mapped using graptolite stages and zones. The tight, closely spaced folds are arranged in dome-like and basin-like anticlinoria and synclinoria. Individual folds are frequently offset by one or more reverse faults which are bedded on one limb, but cross-cutting on the other, for example in the Bendigo and Chewton goldfields. These major structures are cut by a number of large meridional high-angle reverse faults with westerly hade, for example the Whitelaw Fault which forms the eastern limit of the Bendigo goldfield. South of Lancefield, the only Upper Ordovician on the western side of the Heathcote Axis is largely grits and sandstones with a fragmentary neritic fauna (Riddell Grits), indicative of marine regression from western Victoria towards the end of the Ordovician. Towards the Ballarat-Wedderburn line, Lancefieldian outcrops over a wide belt, and at Ballarat 10, OOO ft. of beds occur beneath known Upper Lancefieldian. Further westwards the bedrock sediments are similar lithologically to those in central Victoria, but fossils are entirely unknown. Although usually presumed to be Early Ordovician in age, there are indications that part at least are probably Cambrian. The prominence of slaty cleavage and fissuring suggests greater compression than in central Victoria. On the Cflenelg River near the South Australian border, the sediments are
12 3 somewhat calcareous, including a thin limestone, and are intruded by basic dykes which have been subjected to the same metamorphism as the sediments (Wells, 1956). Between the Heathcote and Mt. Wellington Axes, Ordovician protrudes through the blanket of Silurian-Devonian only in the Mornington Peninsula anticlinorium, and in association with intervening major axes (Ch. 18). On the latter, the sequences are frequently in narrow fault slices and fragmentary. The Upper Ordovician is predominantly dark pyritic shale. Of special significance are the occurrences of granular phosphate rock in Lancefieldian at Phosphate Hill (Mansfield), and in Darriwilian on the Howqua River, and of Lancefieldian limestone with a trilobite-brachiopod fauna, faulted against Cambrian greenstones at Waratah Bay. These suggest to the writer that- the Ordovician on the axes was deposited on intermittently rising anticlinal structures with subsequent preservation by comparatively minor faulting. This best explains the evidence of slow deposition and presence of neritic limestone. Eastwards from the Mt. Wellington Axis the bedrock consists of tightly folded greywackes and Slatés, usually very strongly crushed. Graptolite localities scattered throughout the region date them as late Darriwilian to Eastonian, although the age limits may be wider, Epi-Ordovician deformation and igneous activity_. At the end of the Ordovician the differentiation of eastern and central Victoria into eutectonic and miotectonic zones respectively first became obvious. Whereas in central Victoria the Ordovician and Silurian are essentially conformable, the whole of eastern Victoria was subjected to intense deformation. This deformation - the so-called Benambran 0rogeny' - affected south-eastern New South Wales as well, and has been dated at Canberra within the limits of late Eastonian and late Llandoverian. Immediately following this deformation, a wide belt stretching from Albury in the north through Omeo to Ensay in the south was metamorphosed to a variety of schists, gneisses, and granulites, with the concurrent intrusion of a suite of granites and granodiorites, many of which show gneissic banding (Crohn, 1950). The metamorphic belt is gradational eastwards into unaltered Ordovician, whereas the we stern boundary is frequently a massive shear zone bringing gneis ses into juxtaposition with sediments (Beavis, 1962). East of the main metamorphic belt are similar granitic intrusions surrounded by wide aureoles of schist, WhiC11 are believed to be contemporaneous (Edwards and Easton, 1937). The date of deformation of the sediments we stwards from Ballarat is unknown but is quite, likely to be older than the Devonian age currently ascribed to it. A metamorphic belt similar to that in eastern Victoria occurs in the far west where high grade schists contain granitic intrusions, in part gneissic (Wells, 1956). lntrusions adjacent to this belt, such as the A.rarat granodiorite and the Pyrenees granite, have similar strongly schistose aureoles. SILURIAN AND LOWER DEVONIA1L Silurian-Devonian of central Victoria. In contrast to the Ordovician there is a profound difference between the Silurian successions in central and in eastern Victoria. In central Victoria the Silurian and Lower Devonian are an entity, conformable upon the Ordovician but deposited in a much more restricted area between the Heathcote Axis and the Mt. Wellington Axis (Fig. 1). The Heathcote Axis marks the absolute western limit of Silurian-Devonian and indications are that faulting along it delineated the margin of the rapidly subsiding trough. The rapidity of deposition is shown by Lower Silurian thicknesses of 8, 700 ft. at Lancefield and ll, 500 ft. near Melbourne (Hills and Thomas, 1954), and 24, 000 ft. of Lower Silurian to Lower Devonian at Heathcote. Low-rank greywackes and mudstones still predominate, but subtle changes in lithology are evident. Current ripplemarks and cross bedding are conspicuous while graded bedding is not nearly so common, and the argillaceous sediments are frequently greenish. ln contrast to the Ordovician, it is possible to distinguish lithological units, particularly in the Lower Devonian when regional differentiation also became marked. Vo lcanicity was entirely absent. A diachronous sheet of clean sandstones with conglomerate bands spread into the trough from the west,beginning at Heathcote in the late Upper Silurian. The conglomerate pebbles are normally of stable sediments but igneous pebbles occur near the trough margin in the Heathcote Lower Devonian and also in Lower Silurian conglomerate near Melbourne. Mudstones and silt-
13 4 1- u _T 1. Stavely Axis I.P LOWER PALAEOZOIC I 2 Heathcote Axis LPm LOIIEP, PALAECZCIC METAIIORPIILCS O ORDOVICIAN I 3. Mt. Wellington Axis Om ORDOVICIAN METAMORPHICS S SILURIAN I 4' Waratah Bay AX SD s1i.urian - LOWER DEVONZIAN D LOWER - MIDDLE DEVCNIAN DC UPPER DEVONIAN - LOWER CAREONIFEROIJS / MAJOR Axis I,J FAULT on MoNocL1Iw 1 I if; CAIILDRQII s'rruc'rui=al _ < O II' as r~' I 2. ' I sn I 0 / O 0 Ja X LP 0 ~ s `..I...;_.-A-» ` v»,_ 1 ` DC I I - ' 1? Q Y -I A t *li x 2. I* A '» II* ` DC LP I Ir v 1 if 1' l 6 M ` 0 *.-'1 LPm a,-qi SD SD *' ' Om ' LP 0 i 1, 3. gi O ` ' 0 ' Q-I ~», _/ / D G _ Q QI' 100 M1I_.Es 'I Fig. 1. Synopsis of the Palaeozoic structure of Victoria. nlltlwlnwuvun- I-:NI-lun In [ FAULT on MONOCLINE ' *' ' LIMIT OF MESOZOIC I 1 + UPLIFT. ' -I..I -.._ LIMIT OF UPPER CRETACEOUS P / ' - VOLCANO I' ' ' ' ' ' LIMIT OF MARINE TERTIARY 1 D I I f ' ' ~ Q, ` : / 1' I _/.E ', '. sg ' I': uo:: 3 -& ' I I I I '»'`r~,+l} ` :.. '90 _/' 0 ` *.' / '~.` `~`,/.'.f'----:'t'v-f Q _, ,1. - 'mr 1`, '. an 9 ' ': ' *_ I`,`/ `?.> . I.. {.` _.-:'_: /`//`/-X ` l`/`, 171'.. ``.. `. 0,Ir `/' G 1,/Q. `, /,~' Q,.`/,`, ` 7,_,._;:. _..._._._.-~- ye/*_- ` `_ - `~` If />/`.I-*-*' O W'.' I`l 0 : ' 'I' ~ ` `... 1, '...' Etf '&, X l._.` W- +,_ -_ - `/. I~I_.;l» , / + /I I, / + I -1 '_' &/`. / / * s _-- ` /f _ .` ',`-I.' gé --` ` ` `~ ` ` ~ ` I ` MILES ~ _, 1 Fig. Z. Synopsis of the post-p111tcozoic structure of Victoria, sho wing the distribution of Mesozoic Volcanic and Tertiary sediments and Newer vents.
14 5 stones with rich shelly faunas characterize the Lower Devonian at Kinglake and Lilydale (type Ye ringian), with a lenticular coral-stromatoporoid limestone intercalated at Lilydale. In the eastern portion of the trough the early Lower Devonian is typified by pelagic faunas, the Monograptus-Baragwanathia association, now regarded as early Lower Devonian (Jaeger, 1962), and the specialised Tanjilian' fauna with the lamellibranch Panenka, orthoconic nautiloids, and pteropods'. The widespread occurrence of land plants in these and in the succeeding Walhalla Series implies the existence of a contiguous land area, almost certainly to the eastward. The very thick Walhalla Series consists of shales and slates with rhythmic sandstone and spasmodic thick beds of relatively clean fossilife rous grit, echoes of the Basal Grits. The 'Basal Grits' of the Walhalla Series are a persistent horizon of fossilife rous shallow-water conglomerates and sandstones, and lenticular limestones which accumulated on local shoal areas. Cambrian greenstone pebbles in some of the conglomerates indicate that one of the Cambrian axes to the east was exposed to erosion. In the Silurian-Devonian, neritic shelly faunas become progressively more conspicuous. Conversely graptolites,ubiquitous in the Ordovician, occur only spasmodically, usually in narrow bands. All in all, deposition was predominantly neritic with local intermittent areas of deeper water as, for example, while the Monograptus-Baragwanathia dark shales accumulated. The youngest assemblages known indicate that sedimentation finally ceased late in the Emsian or perhaps early in the Eifelian. The structure of the Silurian-Devonian shows a contrast between west and east. In the western sector the folds are simple persistent structures, with several simple domes and basins. Cleavage and fissuring are subordinate. Deformation was more intense in the eastern sector with the production of anticlinoria and synclinoria. The Mt. Easton and Mt. Useful Axes flanking the Walhalla Synclinorium are complex faulted structures bringing up Ordovician in their cores (Ch. 18). Cleavage and fissuring become progressively more intense eastwards particularly in the eastern limb of the Walhalla Synclinorium which has been severely crushed against the trough margin. Major structure pattern in eastern Victoria. Eastern Victoria and contiguous parts of New South Wales entered a rather different tectonic regime because of the stabilization at the end of the Ordovician with development of a more competent substrate. East of the metamorphic belt, large faults divide the region into a mosaic of large phacotic blocks. One such fault has been traced from Bindi down the Indi River and into New South Wales as far as the latitude of Canberra. This pattern of augen-like blocks is considered to be the result of 'flattening' by compression from the east, with considerable shearing in the bounding fault zones. We stwards into the less disturbed metamorphic belt the pattern changes into two conjugate fault sets, one NNW-SSE parallel to the regional trend, the other NE-SW. These faults were certainly active at the end of the Silurian and probably earlier as determinants of Silurian sedimentation. Variations in both thickness and lithology suggest that various blocks behaved differently, either sinking rapidly or slowly, or remaining positive. Silurian of eastern Victoria. The Silurian in this eutectonic region contrasts strongly with that in central Victoria. At Wombat Creek, north of Omeo, a Silurian sequence occupying a narrow graben begins with the thick sub-aerial Mitta Mitta River rhyolites, including ignimbrites with xenoliths of Ordovician sandstone and slate, and of granite. This is overlain by a massive conglomerate formation containing rhyolite pebbles in addition to sandstone, slate, and granite. The upper fossiliferous beds are mainly shales, with interbedded conglomerates, sandstones, and lime stones. At Limestone Creek near the New South Wales border the Silurian is represented by very thick low rank greywackes and mudstones, with subordinate lime stones and clean quartz sandstones (Talent, 1959). At Quedong near Bombala, N.S.W., a simple gentle basin structure contains a relatively thin sequence of quartz sandstones, followed successively by limestones and calcareous shales. An outlier of the basal sandstone forms the monadnock of Mt. Delegate near Bendoc. The shelly faunas in all these sequences indicate a Middle or Late Silurian age but the beginning and end of sedimentation cannot be dated (accurately. Epi-Silurian deformation and igneous activitl. At or about the end of the Silurian another period of deformation affected eastern Victoria - the so-called Bowning 'Orogeny' - but because of the more competent bedrock, it was expressed largely as major faulting. The thick Limestone Creek sequence was strongly folded whereas
15 6 the thin Quedong sequence was protected. Likewise the Wombat Creek sediments, while steeply inclined, escaped strong folding because of the underlying competent rhyolites and conglomerates. The Limestone Creek Silurian has been intruded by the southern end of the Kosciusko mas sif and weakly metamorphosed to low-grade schists and marble (Talent, 1959). The relationships between the major fault pattern and intrusions, such as the Murrumbidgee and Kosciusko Batholiths in New South Wales, suggest that foundering of fault blocks has been responsible for their emplacement. Metamorphism has been insignificant in comparison to the size of the intrusions. LOWER AND,MIDDLE DEVONIAN. East of the Mt. Wellington Axis, Silurian rocks were apparently absent over a wide belt, for at Tabberabbera transgressive Lower, to early Middle, Devonian rests with violent unconformity upon Upper Ordovician (Talent, 1963). This neritic sequence, some 8,000 ft. thick, links the geosynclinal Lower Devonian of central Victoria, already discussed, with the marine Devonian of eastern Victoria. Basal conglomerate and coarse quartz sandstones pass up through thick silty sandstones and fhales, with an Emsian shelly fauna, into dark shales and minor lime stone bands of Eifelian age. The whole is folded into a strongly plunging synclinorium with a remarkable northerly extension as a long simple syncline. Further east the epi-silurian deformation and intrusion was followed by another deposition cycle similar to that of the Silurian, but showing the effects of still greater bedrock stability. At Limestone Creek both the Silurianiand succeeding granodiorite are overlain with strong unconformity by the sub-aerial Snowy River Volcanics (Talent, 1959). These extend southwards to Buchan and Nowa Nowa in a general synclinal structure and consist of albitized rhodacites with sub-ordinate pyroclastics and latite flows (Ringwood, 1955), and local intercalations of non-marine conglomerates and sandstones (Fletcher, 1963). The volcanics, normally 2000 to 2500 ft. thick, reach a maximum of 10, 000 ft. about 30 miles north of Buchan where they represent flood extrusions from fault fissures. South of Buchan thin intercalations of fossiliferous sandstone presage the marine transgression which followed. At Buchan the neritic marine sequence, up to Z, 800 ft. thick (Teichert and Talent, 1958), began with thin clastic sediments including arkose, rapidly succeeded by the uniform Buchan Caves Limestone, the lower part of which is dolomitized. The upper bedsgrade laterally southwards from bedded lime stones, dark calcilutites, and calcareous mudstones into slightly deeper water mudstones and nodular muddy lime stones. In places richly fossiliferous massively bedded lime stones have been interpreted as bioherms, but, in fact, true reefs are not present. The Shelly faunas, principally of corals, stromatoporoids, and brachiopods, range in age from Emsian in the Buchan Caves Limestone to Upper Eifelian. Similar Devonian sequences are found at Bindi, Limestone Creek, and on the Erinundra River. Because of the thick competent lavas the major structures are broad and open, with strike faulting and disharmonic folding of the sediments forming a synclinorium at Buchan. At Waratah Bay, Lower Devonian Siegenian lime stones with a gritty basal phase re st unconformably upon greenstones of the Cambrian axis and are followed disconformably, by dark Emsian lime stones (Talent, personal communication). This sequence is separated by a major boundary fault from homologues of the Walhalla Series - the Liptrap Formation - which may extend into the early Middle Devonian._ This contemporaneity with the limestones emphasises the contrast between shallow water deposition on the Cambrian axis and the accumulation of clastic sediments in the flanking deeper water trough. Late Middle Devonian deformation. Eastern and central Victoria we re subjected to the (last major deformation - the socalled Tabberabberan 'Orogeny' which can be dated within the limits of late Middle and early, Upper Devonian. The resultant structures are much more spectacular in central Victoria where they developed in unconsolidated sediments, whereas in eastern Victoria movement was largely absorbed by the major fault lines. Epi-Middle Devonian igneous activity. An episode of igneous intrusion followed the late Middle Devonian deformation but antedated all the Upper Devonian rocks. The Woods Point dyke swarm (Hills, 1952) is concentrated in the
16 7 western limb of the Walhalla Synclinorium, dykes decreasing in abundance westwards and being absent from the more strongly crushed eastern limb. The dykes generally follow regional strike but are cross-cutting in section. Diorites and hornblende lamprophyres predominate although the composition ranges from quartz porphyry to perknite and peridotite. Many dykes have suffered later compression with the development of conjugate shear-plane fractures which have acted as loci for the introduction of auriferous quartz reefs - the ladder veins of the Morning Star and other mines. Similar diorite dykes at Tabberabbera are accurately dated, cutting Eifelian but truncated by the Upper Devonian. A petrologically related hornblende granodiorite at Mt'. Buller, east of Mansfield, antedates Upper Devonian lavas (see Ch, 18) and the similarly situated Mt. Taylor granite porphyry stock near Bairnsdale is probably contemporaneous. UPPER DEVONIAN AND LOWER CARBONIFEROUS. With the whole of Victoria largely stabilized, thick non-marine sedimentation during the Late Devonian and Early Carboniferous was restricted to two graben structures, one in the Grampian Ranges of western Victoria, the other on the eastern flank of the erstwhile Silurian- Devonian trough of central Victoria. Typical fluviatile red beds are characteristic, with plant fossils and occasional fish faunas. Upper Devonian cauldron volcanics and intrusives. Acid Volcanics are wide spread in the Upper Devonian. ln central Victoria volcanicity was concentrated in a number of rounded and polygonal cauldron subsidences, several skirted by ring dykes, which contain piles of lavas up to 5, 000 ft. thick (Hills, 1959). Initially, relatively thin acid lavas and ignimbrites, with subordinate ande site and basalt, were extruded from central vents. Pyroclastics occur spasmodically and one of the rare lenses of clastic sediment contains Late Devonian fishes at Taggerty. At the northern end of the eastern Upper Palaeozoic belt (north of Mansfield) conglomerates are interbedded with rhyodacites and have been locally folded prior to the main cauldron lavas (Brown, 1961). During the second phase, the final cauldron collapse, flood extrusions of nevadite, rhyodacite, and hypersthene dacite, individually up to ft. thick, filled the cauldrons in one or several stages. Finally, granite and granodiorite intrusions were emplaced by major stoping adjacent to and into the Volcanics. North of Mansfield, granite intruding unfolded Upper Devonian cauldron lavas is in turn overlain unconformably by Lower Carboniferous sediments (Brown, 1961). A number of other high level discordant granitic batholiths in central Victoria, sometimes showing evidence of the same emplacement mechanism, can be reliably correlated with these epi-upper Devonian intrusives. All have unstressed hornfels metamorphic aureoles. Hills (1959) has recognized a cauldron subsidence in north-easte rn Victoria where the thick Jemba nevadite is surrounded by a quartz porphyry ring dyke. This, together with the nearby Pine Mountain and Mt. Mittamatite red granites, which transect a consanguineous swarm of NE- SW trending dykes ranging from quartz porphyry to diorite and labradorite porphyrite (Edwards and Easton, 1937), is likely to represent slightly older igneous activity (Ch. 19), Upper Palaeozoic sedimentary sequences. The Upper Palaeozoic sequence in we ste rn Victoria began with extensive rhyolites and minor trachytes. The overlying Grampians Sandstones were deposited mainly in a rapidly subsiding graben, with thinner sections on the flanking aprons. Within the graben their base is covered ; even so 20,000 ft. of beds are exposed. A thin basal phase of conglomerates, with pebbles of rhyolite and granite as well as sediment, is followed by a remarkably uniform succession of pale cross-bedded quartz sandstone, siltstone, and shale (Spencer-Jones, 1961). Near the top of one of the se - the Silverband Formation - is a thin marine inte rcalation with a small undiagnostic fauna (Talent and Spencer-Jones, 1963). The Grampians Sandstones certainly include Upper Devonian and are likely to extend into the Lower Carboniferous. Within the graben they have been down-faulted and tilted to the we st. Where the boundary faults converge towards the north strong drag on both margins has produced a closed syncline. Within the graben, they have been intruded by sills of quartz porphyrite and stocks of granite and granodiorite. In the eastern Upper Palaeozoic belt, more complex in history and structure, the depositional basin approximates to a graben trending NNW-SSE with the bounding structures evident in places. The belt is subdivided by conjugate anticlinal structures trending NNE-SSW.
17 8 In the South Blue Range at Mansfield the Upper Devonian sediments, interbedded sandstones and mudstones with fish, are underlain by basal muddy conglomerates lacking igneous pebbles and capped by a thin rhyodacite ignimbrite. These beds have been folded into a tight synclinorium prior to the deposition of the Carboniferous (see Ch.l8`).: The Carboniferous of the Mansfield Basin begins with sandy basal conglomerates, containing igneous pebbles and intercalated arkoses where overlying lavas, followed by a return to red-bed sedimentation. Lower Carboniferous fish occur some distance above the base. In the remainder of the belt, Upper Devonian and Lower Carboniferous are concordant and have not been differentiated yet. The basal phase, of proven Upper Devonian age, consists of widespread volcanics with local interbedded sediments, largely conglomerates. Individual flows are thin and predominantly rhyolitic, with subordinate basalts. Further conglomerates are followed by many thousands of feet of red beds. Locally lava flows persist for some distance and, in contrast to the Grampians sequence, pale sandstones are subordinate. Upper Palaeozoic deformation. Internally these Upper Palaeozoic rocks have been only gently deformed into broad open folds but in proximity to some of the Lower Palaeozoic contacts, particularly on the western margin of the belt, strong deformation has occurred. These boundaries are usually fault folds which have even caused local overturning in the Carbonife rous (see Ch. 18). In places clean fractures form the boundary, and on the Barkly River Cambrian greenstones have been thrust over the Upper Palaeozoic (Harris and Thomas, 1954). This compression along the we stern margin of the belt, the shearing of the Woods Point dykes, and reversed faulting of some of the epi-upper Devonian quartz reefs, for example in the Wattle Gully Mine, Chewton, mark the final pulses of tectonic activity in the Victorian Palaeozoic. After the Lower Carboniferous, tectonic instability connected with the eastern Australian mobile belt finally ceased. PERMIAN AND TRIASS_IC_= A period of tectonic quiescence intervened during the Permian and early Mesozoic. The Permian is represented by glacial and fluvio-glacial sediments usually preserved from erosion by down-faulting. They are normally flat-lying and, in the absence of any overburden, often so poorly lithified as to resemble Pleistocene tills. The sequences are comparatively thin, except at Bacchus Marsh where several thousand feet occupy an east-west graben, the first indication of a new tectonic regime. A thin marine band with Notoconularia has recently been discovered towards the top of this sequence (Thomas, l9f69' ), which is capped by beds containing Triassic plants. At Benambra, near Omeo, are a number of stocks of granite porphyry and quartz syenite, some of which intrude their associated trachytic lavas and tuffs for up to 1, OOO ft. As the base of the lavas corresponds to the erosion surface of the time, plutonic rocks were intruded well above the surrounding bedrock. A recent K-Ar dating by the Australian National University gave a late Triassic age of 202 and 207 million years (McDougall, personal communication), making it the youngest known acidic intrusive in the State. JURASSIC AND CRETACEOUS. Jurassic and, or Lower Cretaceous. The establishment of a new tectonic regime during the Mesozoic led to the initiation of depositional basins spread across the southern portion of the State The South Gippsland basin is - separated by the positive Mornington Peninsula from the Western District basin, which is continuous between its outcrops in the Otway Ranges and Casterton area. The South Gippsland basin is rimmed on the south by Palaeozoic rocks and is thus a separate structure, distinct from the present Bass Strait. With over 9,000 ft. of deposition, subsidence was extremely rapid. The exclusively fluviatile sediments consist of greenish grey cross-bedded feldspathic sandstones approximating to arkoses,monotonously alternating with grey mudstones and shales (Edwards and Baker, 1943). Grains of ande site of unknown source occur in the arkoses. Exotic conglomerates occur at the base while autochthonous conglomerates are common throughout. The Wonthaggi-Korumburra area of South Gippsland contains thin bituminous drift coals, formerly mined. Plant fossils
18 9 are common, with rare fish remains. On the basis of plant remains these rocks were assigned to the Jurassic, but recent palynological studies have dated them as between the base of the.cretaceous and the Aptian to Albian (Dettmann, 1963). These sediments now outcrop in late Cainozoic structures discussed below. There is little discordance between them and the flanking't 1`tia1`Y 1` C ks» but in the Balook Dome of South Gippsland overstepping by Eocene basalts indicates quite considerable pre-tertiary upwarping (Edwards, 1942). Upper Cretaceoug ln a separate episode, up to 3, OOO ft. of neritic Upper Cretaceous was deposited during a marine transgression on to the coastal belt of western Victoria between Port Campbell and Nelson on the South Australian border (Baker, 1961; Taylor, 1964). Around Port Campbell a simple marine cycle of shallow water sandstones and siltstones grades outwards into dark mudstones, in part glauconitic and pyritic, containing Turonian and Santonian foraminife ra and an ammonite. These are completely overlapped without any obvious break by marine Paleocene. ln the Nelson bore, quartz sandstones predominate. CAINOZOIC. The entire Tertiary succession is represented in Victoria but in no single section (maximum thickness 4, 500 ft.) is it complete. The principal depositional areas, now lowlands, are the Gippsland Basin with a synclinal extension we stwards into the Latrobe Valley, the Westernport and Port Phillip sunklands separated by the Mornington Peninsula, the Western District plains, and the Mallee and Wimmera regions in the north-we st of the State which form the south-easte rn portion of the Murray Basin. Complications in the stratigraphy are largely the result of the interplay between three depositional environments. The coal measures environment is represented by stable clastic sediments from conglomerates to clays, with the accumulation of extremely thick seams of brown coal in favourable situations. Coal measures deposition was widespread during the Paleogene and persisted locally into the Early Miocene. The marine deltaic environment, typified by the Angle sea Sand and Dilwyn Clay, is represented by fine-grained carbonaceous pyritic clastics deposited rapidly under anaerobic bottom conditions, due more to an excess of organic matter than to poor circulation. The carbonaceous matter and abundant pollen was supplied by plant debris washed and blown in from the adjacent land. A benthonic fauna is absent, the foraminifer Ha_plo_phra_gm_o_ides being the only common fossil. However occasional thin intercalations of better aerated sediment do carry small shelly faunas. Sediments of this environment range in age from Paleocene to Early Oligocene, being contemporaneous with the coal measures forming on the adjacent land. As such, they occur either overlying or seawards from the coal measures sequences. The normal marine environment is further divisible into shallow water neritic, characterized by polyzoal lime stones with echinoid-brachiopod-pectinid faunas, and slightly deeper water neritic with glauconitic marls and clays containing rich molluscan faunas. Marginal grits, sometimes glauconitic and invariably fe rruginized in outcrop, are subordinate. Thin phosphatic nodule beds occur at the base of transgressive units and periods of condensed, deposition are marked by nodule beds or greensands. From the Paleocene to Early Oligocene because of the wide spread marine deltaic environment and the influx of clastic detritus, normal marine deposits were localized and lime stones uncommon. They became wide spread following marine transgression which was intensified in the Late Oligocene (Janjukian) and reached a :maximum in the Miocene. Deposition of Upper Oligocene to early Upper Miocene limestones, marls and clays with the entry of clastic detritus at a minimurn, indicates low relief in the highlands over this time. During the Late Miocene the sea began to fill up and a greater influx of detritus led to the deposition both then and in the Lower Pliocene of regressive shallow water sands and clays, and an absence of limestone. The sea was then expelled from most areas except the far south-west, where a separate local transgression in the Late_Pliocene (Werrikooian) and Early Pleistocene is represented by shallow water shell beds and oyster limestones. Rejuvenation of the highlands which began in the Late Miocene reached a climax in the Late Pliocene and Pleistocene, shown by widespread conglomerates and sands, such as the 'Torrent Gravels in Gippsland. Similar, perhaps older, deposits constitute the overburden to the Latrobe Valley coal measures and have been displaced by local structures. Quaternary sediments include widespread dune and sheet
19 10 sands in the Mallee and south-western Victoria, alluvial deposits in the Wimmera, Northern Plains and Gippsland Plains, and Pleistocene coastal dune limestone. Gypsum and rock salt deposits occur in playas in the Mallee. Palaeogene_ coal measures contain some of the thickest brown coal seams in the world. In the Latrobe Valley several major seams, separated and subdivided by impersistent clay splits, reach a maximurn total thickness of 1000 ft. (Gloe, 1960). Thick seams also occur around the South Gippsland Hills, ufnder the We rribee Plains between Melbourne and Bacchus Marsh, and on the eastern and northern flanks of the Otway Ranges (Thomas and Baragwanath, ). On the Gippsland Shelf petroleum and natural gas occur in Cretaceous and Tertiary horizons (James and Evans, 1971; Griffith and Hodgson, 1971). lt is of historical interest that the first oil produced and marketed in Australia came from a Lower Oligocene greensand at Lakes Entrance.) Cainozoic volcanic activity. The Cainozoic was a period of basic volcanicity grouped about two maxima in the Eocene and Plio-Pleistocene, but linked by spasmodic flows in the Oligocene and Miocene. The Eocene Older Volcanics are concentrated to the east of Melbourne, both in South Gippsland and the highlands, whereas the Newer Volcanics lie almost entirely to the west of Melbourne, forming the Werribee and Western District lava plains, and valley flows in the western highlands. The Older Volcanics, locally more than 1100 ft. thick, are olivine basalts averaging 45 per cent SiO2 with unsaturated differentiates such as nephelinite, tinguaite, and phonolite. On the other hand the Newer Volcanics, up to 500 ft. thick, average 50 per cent SiO2, with saturated alkaline differentiates including alkaline basalt, trachyte and soda trachyte. While the Newer Volcanics began in the Pliocene, they invariably overlie the marine Tertiary, including Upper Pliocene marine, and are largely Pleistocene, continuing into the Holocene. The physiographic features of the youngest volcanoes and flows are practically unaltered by weathering. Cainozoic tectonic activity; Mild tectonic activity occurred intermittently through the Tertiary with downwarping in the sedimentary basins and active faulting in the Palaeozoic rocks, f01 example 011 The most obvious movements, however, took place during and after the Pliocene. A series of en echelon domal uplifts elongated in an ENE WSW direction and bounded by monoclines and, faults, is located on the site of the former Lower Cretaceous troughs. Initiated prior to Upper Cretaceous sedimentation, these were rejuvenated and accentuated during the late Cainozoic. They continue out on to the Gippsland Shelf where structures form reservoirs for major natural gas and petroleum accumulations. Se1WY1'1'S Fault At the same time the highlands of Victoria were elevated along an E-W axis, and N-S faulting, some of it very recent, occurred along pre-existing fault lines or on new structures such as the Rowsley Fault. PH YSIOGRAPHY. The east-to-we st backbone of the Victorian Highlands separates the Murray Basin Plains on the north from a series of lowlands grouped together by Gregory as the 'Great Valley' of Victoria, in turn flanked on the south by the youthful uplifts of the Southern Uplands (Hills, 1940, 1955). Victorian Highlands. While continuous topographically with the NNE trending highlands of New South Wales, the Victorian Highlands owe their origin to the tectonic regime which controlled Mesozoic and Tertiary sedimentation rather than to the primary westerly directed forces operating along the east coast of the continent. They approximate to a broad E-W anticlinal arch with a gentle westerly plunge, modified in detail by pre-existing Palaeozoic trends. Remnants of at least three erosion surfaces are recognizable, the youngest of which, carrying Older Volcanic residuals, is at the latest early Tertiary in development, implying that the two higher surfaces are pre-tertiary and perhaps of great antiquity. The highlands are conveniently divided into eastern and we ste rn sections by the Kilmore Gap north of Melbourne. The eastern highlands are similar to contiguous New South Wales, and preserve extensive tracts of the higher erosion surfaces, particularly the middle one, forming the Fig. 3 (opposite). Geological map of Victoria and adjoining south-eastern New South Wales.
20
21 11,» 1 6 `s I 1 _ f'~~ ' ' b `V( ` nunuv `~_ nlsm ruin; 'I 'N /2-5 '_a`_,z> ' -.J X trr- A VICTORIAN _ If HIGHLANDS 4'~~»;»`` #_/-'J ' L Q,.»' xo Q*,f ` ' ` I .-I ` af $9 ` ` ' '_, If 6 D,I 8 O.-'» SOUTHERN`,- r w. L mmns ~.f Q..& _ <& 7 W e vp ` 7 '& AQ o` .<. LANDS 6 - o loo 5 f nu I Fig. 4. Major Physiographical Divisions of Victoria showing - Murray Basin Plains l. Mallee, 2. Wimmera, 3. Northern Riverina Plain -_Xictorian Highlands 4. Western Highlands, 5. Eastern Highlands - Southern Lowlands 6. Western District Volcanic Plain, 7. Coastal Plains, 8. Port Phillip Sunkland, 9. Westernport Bay Sunkland, 10. Gippsland Plain - Southern Uplands, including from west to east, Otway Ranges, Barrabool Hills, Mornington Peninsula, South Gippsland, Wilson's Promontory. various 'High Plains'. Some of the se carry Older Volcanic residuals and they decrease in elevation progressively we stwards from nearly 6000 ft. on the Bogong High Plains to under 2, 000 ft. on the Kinglake Plateau. The upper surface is seen to the east of Melbourne in ranges of Devonian igneous rocks with flattened summits, and in monadnocks such as The Cobberas further east. Dissected ranges with concordant summits fall away from these plateaux, evenly to the south and more disjointedly to the north. Discontinuities and local elevation also result from movement on preexisting fault lines such as the Indi fault system and Tawonga thrust. The early Tertiary surface is largely confined to the flanks of the highlands, occurring at elevations of up to 2, 000 ft. Rugged mountains are the exception, the most spectacular being formed by erosional edges of the Upper Palaeozoic belt and by some igneous bodies. Evidence of Pleistocene glaciation is entirely wanting although local solifluction effects are known. The major streams draining to north and south off the arch are entrenched for as much as 3, 000 ft. below interfluves and have developed narrow alluviated flood plains within the highlands. The we stern highlands differ principally in the much more widespread development of the early Tertiary erosion surface, with scattered residuals upon it forming isolated. ranges up to andabove 3, 000 ft., of which the Upper Palaeozoic strike ridges of the Grampians are the largest. The arched early Tertiary surface shows seve ral local culminations. It reaches 2., 500 ft. in a domal uplift centred on Trentham. The Dundas Tableland is a late rite capped uplift with associated faults, forming the western limit of the highlands, with the Glenelg River flowing around' it. Deep dissection of the early Tertiary surface occurs in the neighbourhood of youthful fault scarps, notably the Rowsley fault. Between the Kilmore Gap and the Ballarat district, the Newer Volcanics occur as valley flows and small lava fields emanating from a multitude of vents, over 200 of which occur within the domal uplift mentioned above. The pre-volcanic streams have been displaced late rally but the re is 'little evidence of major disruption of drainage. Murray Basin Plains. The plains north of the highlands are divisible into three regions - the Mallee, Wimmera, and Northern Rive rine Plain. The semi-arid Mallee is underlain by marine Tertiary rocks of the Murray Basin and is typified by a system of east-we st fixed sand dunes, salt lakes and gypsum ('copi') deposits, and the absence of permanent streams. Gentle structures in the underlying Tertiary are expressed as broad ridges and depressions.
22 12 The riverine plain of northern Victoria consists of an alluvial sheet several hundred feet thick, formed by aggradation by the Murray River and its tributaries, helped by uplift of the Tertiary of the Murray Basin in South Australia. Gradients are extremely low (3-5 ft. per mile), and lakes, frequently with bordering lunettes, occur in low-lying areas. A few residual hills of Palaeozoic rocks are isolated in the plain. Minor fault movements along the northern extension of the Heathcote Axis produced the Cadell Tilt block diverting the Murray River southwards through Echuca. The natural western extension of this riverine plain is the Wimmera, with its characteristic black soils. Towards the South Australian border sand ridges and lakes become numerous. Southe rn Lowland s. The lowlands of southern Victoria are formed by a series of structures of Tertiary age. The Western District Plains consist of a sheet of Newer Volcanic basalt flows largely overlying marine Tertiary. The youngest Volcanics, geologically Recent, are excellently preserved - the cones with craters, and the flows with broken surfaces ( stony rises'). Lake - filled maars are common particularly along the southern border of the plain, and Sha11OW lakes such as Lake Corangamite occupy depressions in the lava plain. In-the far south -we st, beyond the Kanawinka Fault, the Tertiary coastal plain carries a system of coastal calcareous dunes of Quaternary age with intervening sand sheets. _ The Port Phillip and We sternport sunklands, separated by the Mornington Peninsula horst, are downthrown by late Cainozoic faulting, with marine inundation of the lowerlying portions. Port Phillip Bay is land-locked by a bar of Quaternary dune limestone and sands. The Gippsland Plain covers the Tertiary Gippsland Basin with the Latrobe River and Gippsland lakes situated on the main synclinal axis. Its northern junction with the highlands is a series of faults and flexures which also delineated the edge of the sedimentary basin. The plain is covered by anapron of torrent gravels with lower alluvial flood plains along the rivers. The westward extension of the Gippsland Plain occupies the Latrobe Valley syncline and the depressed block north of the Strzelecki Ranges. Southern Uplands; The Otway Ranges and South Gippsland Hills are the topographic expression of the series of domal uplifts across southern Victoria. Each is a double structure, the latter with minor fault blocks between the two main domes. Their topography results from late Cainozoic uplift with the pre-uplift surface shown by concordant summits to the ridges. Smaller uplifts form the Barrabool Hills and Bellarine Peninsula near Geelong, and the Baragwanath anticline in Gippsland. Adjacent to these uplifts are coastal plains in Tertiary sediments showing evidence of post-miocene planation and late ritisation. The Mornington Peninsula and the granitic Wilson's Promontory were elevated at the same time. REFERENCES. Baker, G., Studies of Nelson bore sediments, western Victoria, Geol. Surv. Vic. QQ. 58. Beavis, F.C., The geology of the Kiewa area, Proc. Roy. Soc. Vic., 75: Brown, M.C., 1961.' The geology of the Tatong-Tolmie area, M.Sc. Thesis, University of Melbourne (unpublished). Crohn, P.W The geology, petrology and physiography of the Omeo district, north-i, eastern Victoria, Proc. Roy. Soc. Vic., 62: Dettmann, M.E., Upper Mesozoic microfloras from south-eastern Australia, Proc. Roy. Soc. Vic., 77: Edwards, A. B A donde-like structure in the Jurassic rocks of South Gippsland, Proc. Roy. Soc.gVic., 54: Edwards, A.B., and Baker, G., Jurassic arkose in southern Victoria, Proc. Roy. Soc. _'LLc_., 55: Edwards, A. B., and Easton, J.G., The igneous rocks of north-eastern Benambra, Proc Roy. Soc. Vic., 50:
23 13 Fletcher, K., The Snowy River volcanics west of Buchan, Victoria, Proc. Roy. Soc. Vic., 76: Gloe, C.S., The geology of the Latrobe Valley coalfields, Proc. Aust. lnst. Min. 7 _:L/igg., No. 194: Griffith, B. R., and Hodgson, E.A., Offshore Gippsland Basin fields, Jour. Aust. Petrol. Explor. Assoc., 2(1): Harris, (W. J.,' and Thomas, D.E., 1938.` A revised classification and correlation of the Ordovician graptolite beds of Victoria, Min. Geol. Jour., 1(3): Harris, W. J., and Thomas, D.E., Notes on the geology of the Wellington-Macalister area, Min. Geol. Jour., 5(3): Hills, E.S., The Physiography of Victoria. Whitecombe and Tombs. Hills, E.S The Wood s Point dyke swarm, Victoria, in Sir Douglas Mawson Anniversary Volume, pp (University of Adelaide Adelaide). :, Hills, E.S., Physiography and Geology in lplcroducing Victoria (ed. G. W. Leeper), pp (A.N. Z.A.A.S.: Melbourne). Hills, E.S., Cauldron subsidences, granitic rocks, and crustal fracturing in S.E. Australia, Sonderdrtlck Geol. Runds., 47: Hills, E.S. and Thomas, D.E Turbidity currents and the graptolitic facies in, Victoria, Jour. Geol. Soc. Aust., 1: Jaeger, H., Das Silur (Gotlandium) in Thuringen und am ostand des Rheinischen Schiefergebirges, Simpogsium Silur/Devon-Grenze 1960, p. 131 (Stuttgart). James, E.A., and Evans, P. R., The stratigraphy of the offshore Gippsland Basin, Jour. Aust. Petrol. Explor. Assoc., Z(1): Ollier, C.D. and Joyce, E. B., Volcanic Physiography of the Western Plains of Victoria. Proc. Ro_y. Soc. Vic., 77(2): Ringwood, A.E The geology of the Deddick-Wulgulmerang area, East Gippsland, Proc., Roy. Soc., Vic., 67: Spencer-Jones, D., The geology and structure of the Grampians region, Ph.D. Thesis, University of Melbourne (unpublished). Talent, J.A Notes on Middle Palaeozoic stratigraphy and diastrophism in Eastern, Victoria, Min. Geol. Jour., 6(3): Talent, J.A The Devonian of the Mitchell and Wentworth Rivers, Geol. Surv. Vic., Mem. 24. Talent, J.A., and Spencer-Jones, D The Devono-Carboniferous fauna of the Silverband, Formation, Victoria, Proc. Roy. Soc_. Vic., 76: Taylor, D. J., Foraminifera and the stratigraphy of the Western Victorian Cretaceous sediments, Proc. Roy. Soc. Vic., 77: Teichert, C. and Talent, J.A Geology of the Buchan area, Gippsland, Geol. Surv., Vic., Mem., 21. Thiele, E, O., Notes on the Dolodrook serpentine area and the Mt. Wellington rhyolites, North Gippsland, Proc. Roy. Soc. Vic., 21: Thomas, G_A_ Notoconularia, a new Conularid genus from the Permian of Eastern Australia., Journ. Pal., 43: Thomas, D.E The structure of Victoria with respect to the Lower Palaeozoic rocks, Min. Geol. Jour., l(4): Thomas, D.E., and Baragwanath, W Geology of the brown coals of Victoria, Parts, 1-4, Min. Geol. Jour., 3(6): 28-55; 4(l): 36-52; 4(2): 41-63; 4(3): Thomas, D.E. and Singleton, O.P., The Cambrian stratigraphy of Victoria, in El, Sistema Cambrico, su Paleogeografiag, y el Problema de su Base (Ed. J. Rodgers 2: (20thllnt. Geol. Congr.: Mexico City). Wells, B.E., Geology of the Casterton district, Proc. Roy. Soc. Vic., 68:
24 14 CHAPTER 2 GEOLOGY or THE MELBoURNE DISTRICT bv A, H, M. VandenBer_g with contributions by M. A.H. Marsden and J. McAndrew The first phase of the geological history of the Melbourne district is represented by folded Lower Palaeozoic geosynclinal sediments, intruded by Upper Devonian granitic rocks, associated with which are acid Volcanics lying unconformably on the folded sedimentary bedrock. Although sedimentation is known to have occurred in the Lower Carboniferous, Permian and Mesozoic in adjacent regions of Victoria, there is no evidence of further deposition in the Melbourne district until the Cainozoic. Clearly this second phase of the history was largely one of prolonged erosion. ln the third phase, deposition occurred.of a variety of shallow marine terrigenous and minor carbonate sediments, and of non-marine sediments including thick brown coals. These occur especially in the down-faulted Port Phillip and Western Port Sunklands (Fig. l). Periods of basaltic volcanic activity occurred from the Early Tertiary to the Holocene. The Cainozoic sequences are flat-lying and lie with pronounced angular unconformity on the bedrock. The district described in this chapter includes the south-central portion of the Melbourne, and the northernmost part of the Queenscliff l:z50, OOO map sheets (Fig. Z). Reference should be made to more detailed aspects of the geology of Keilor, Lilydale and the Dandenong Ranges in Chapters 3, 4 and 5. Much of the geology of the Melbourne district is closely related to that of the adjacent areas of the Mornington Peninsula, Geelong, Bacchus Marsh, Macedon and Central Victoria (Chapters 6, 7, 8, 9, ll) LOWER PALAEOZOIC In 'central Victoria the bedrock geosynclinal sequence ranges in age from Cambrian to Lower Devonian, but in the Melbourne district the oldest rocks known are Lower Ordovician. In general, lithological units have not been recognised in the Ordovician, the subdivision being based on graptolite zonation. In contrast, lithological changes and regional differences in the Silurian and Lower Devonian rocks enable recognition of major lithological units. The sequences appear to be conformable, and have been folded into a series of anticlinoria and synclinoria. Ordovician. Within the Melbourne district, Lower Ordovician greywackes with interbedded siltstones and shales (Bendigonian to Yapeenian) are restricted in outcrop to a small area west of the Djerriwarrh~Fault. The Upper Ordovician sediments generally cons-ist of siltstones, sandstones and minor shales. They outcrop in a wide belt between the Djerriwarrh Fault and Deep Creek. (Thomas and Keble, 1933; see Ch. 9). Isolated outcrops of Darriwilian age (M. O. 4) are known from the imniediate vicinity of the Djerriwarrh Fault (P. R. Kenley, N. McLaurin, pers. comm. ). The only recognised lithological unit is thethick Riddell Grits (chiefly Gisbornian), which comprises rather well-sorted flys ch-type sandstones, with comminuted shelly fossils. Good outcrops occur on the Calder Highway near The Gap, and on the road between Toolern Vale and Gisborne. Within the Mornington Peninsula Anticlinorium (Keble 1950; see Ch. 6) the Ordovician sequence comprises interbedded siltstones, thin sandstones, shales, and cherty
25 f: 15 ; ; Iihnceheld Y `} / * 5 H;,I Day esford S/ 5' P I Kulmore R 3 F E LL. 42/ yr //{ ' + I / / Glenburn O ' S Q Mt Fraser Q E ig! Gisborne 5 N G O 21 I wh- B %'&5~DA 3 :tt esea. Kinghke é LE_ g I ' 9' U Q 5 >» 2 Y' Q- /Y 9 >~ Q FI/ f E? BALLAN ` 3 <;0NP // Svnbvrv 3 '_ / p 5* I =; / Bacchus Marsh QF ' X Lnyaaue SPR/NG CK `& j Gzensborou h *vg`/ 9 PAL/LT'F` `>, Pom Pu L.P sun <.ANn / MELBOURNE! 4, r/ _. <<~ A /I }- + ' Wg (GOO» ~ ` QV / 4> } / 9% Werribee X 4% / A '_ I Q59 4' .A- 5 * <9 ' 1 *PA I <* // Q + QQ? + + LU Q* + J: I/ Q7 Dandenong + smsanue :N RANGES } / Maude + } ' i ` Ca r rum Swy Sr// + oc' 'E c b Q fan OUYUC Q RL /ffl? FJ C 5 k 5 4 p,9~?`p`% FAULT / Y? QV Q. OJ 'Q J Geelong 5 Franksion / Q I 7 5 5/ 5 éq );'o P 6 Q/Q 15' $' = 4? / Q, / ll - Q 3 4* Y 5' Y' ~i Q Dromana + éi ' /5 H 5f'95 fo $ S' af '' reverse A Devonian volcanics I O FAULT -r' ' normal + Devonian granites / A _,»» M0N0CL NE -Q Cambrian rocks 'K-kv. o miles X kilometres Q) Fig. 1. Structural features of south-central Victoria.
26 16 shales, with a thick horizon of predominantly flysch-type sandstones near the base ( Kangerong Stage'). According to Hills and Thomas (1953) the exposed thickness of the Lancefieldian is about 450 m whereas the rest of the Lower Ordovician is only about 600 m thick (cf m for the Lower Ordovician at Lancefield). Upper Ordovician graptolites are known at the northern end of the Mornington Peninsula (J. J. Jenkin, pers. comm.) and an apparently conformable Ordovician-Silurian sequence is present. Silurian. The Upper Ordovician to Lower Silurian succession is found northwest of Melbourne and its principal features are summarised in Table 1. East and northeast of Melbourne the Lower to Middle Silurian Anderson Creek Formation outcrops in the Templestowe and Warrandyte Anticlinoria (VandenBerg, 1971; Garratt, 1973b). Conglomerates and massive thick greywackes outcropping in the core of the Warrandyte Anticlinorium (Jutson, 1911b) correlate with Unit B and the lower part of Unit C of the Keilor Group (Table 2). They are overlain by a thick sequence of siltstones, often worm burrowed, throughout which arenite beds occur mainly grouped together to form distinct horizons ('bunches'). The formation is at least 1150 m thick and contains Monograptus cf. priodon at Warrandyte (Gill, 1952) and Monograptus testis inornatus near the top of TABLE 1. Stratigraphy and tentative correlation of the Lower Silurian Keilor Group 1 l m l J A C K S 0 N C R E E K LANCEFIELD GRAPTOLITE STRATIGRAPHY GRAPTOLITE FAUNA I ZONES (Thomas and Keble, 1933; (Thomas, 1960) Harris and Thomas, 1949) 'L I LOWER SILURIAN( UNIT C: Thin to thick silt- Stomatograptus australis, (Llandovery) stones,interbedded 'bunches' of Monograptus turriculatus, Springfield crispus greywacke, and at least one M.marri, M.pandus, M.spirato conglomerate horizon. lis permensis, M.crispus, M. Formation turriculatus (Top not known). jaculum, M.priodon, M. undulatus,`m.exiguus. UNIT B (240 m): Thick to very Springfield thick massive greywackes with Monograptus cf. halli, turriculatus interbedded siltstones; several M. turriculatus. Conglomerate conglomerate and pebbly siltstone horizons. Glyptograptus tamariscus, ll UNIT A (1100 m): Thin sand- Diplograptus? sinuatus, Mono Deep Creek gregarius stones and siltstones, sand- graptus Cf- concinnus. 'M» stones often with convolute cf. fimbriatus', M. cf. Formation lamination. gregarius, Dictyonema spp. UP,P1:1i ORDOVICIAN Bolindian Thinly bedded sandstones, siltstones and minor shales. Orthograptus truncatus socialis, 0. truncatus cf. abbreviatus, Climacograptus cf. scalaris miserabilis, C.bicornis, C.missilis, Dicellograptus cf. complanatus pd. cf. caduceus. Fig. 2 (opposite). Geological map of the Melbourne district.
27 ' / r -JI v~ v 0 v PORT / II Belgrave I. ~ 'n'lc.. :':...,',:.. :': -g_, Swamp and /ogoonol deposits:,-~, : -,-.._ cloy, silt, peat, mud. :;.c21g ECENT _ Coastal and estuor;ne deposits; dunes, -',',/, -g - raised beaches: sond, sift, silty cloy. Alluvial flats ond terraces: RECENT. sond, silt, day, grovel. PLEISTOCEN E..., Fan cleposits.. loul, aprons: 9rove', sand. minor sif' granitic sond. ---S0 Newer Volcanics: bosolts, L:J minor limburg;,., scoria. PHILLIP..... ~ G '.n.d ;., ; t... :. i :... quartz d iori,e and '. UPPER _ - Mount Dand.nong Volcanics: '. '. ~ - rhyofit.. rhyoc/ocite;. ',. Z /V, r#t yotloeit. in ' o aureole. > [ ' C ~ Humevale Siltstone: LOWER - ffi siltstone; minor sanastone and limestone. UPPER - =-lid Dorgile Forma tion: laminated and current bedjed sonclstone wi,h interbedded mudstone and shale. EF33c:i;;;3;;;rcci;;;3=icc:i:::3=i5 Mites EF3=C=0i:ecc:i::::i::::::Ei3'O Kilometres Brighton Group and equivolents PLIOCENE _ ~ Bull.nvorcoll Grovels: MIOCENE r..l:j sond, silty sond, grovel, minor.. cloy, ligneous cloy, calcareous.. sand. MIOCENE ~ Sub.Olde, Volcon ic Sediments: ~9rov. l. sand. MIOCENE. ~ Old., Volcanics : oliv;ne, EOCENE ~ titonougit. and augite bosalts. ~ _~'z: ~ ~ _ ~ Glaciol and fluviog/ociol : moui',. to ~ interbedded tiftit., conglomerat. and pebbly siltstone. K.i lor Group Anderson C,.ek Formation: =----fm mo ssive mudstone, interbedded wi,h UPPER... LO. -,Iun sondstone, rhythmlcoll y ''e, WER bedded thin shol. and sandstone.. numerous greywacke conglomerate intervals. ~ Mudstone, claystone, sondstone. UNDIFFERENT I A~O''1::::::::j horn/.ls neor grani te contacts. z: 5-CDARRIWILIAN.. ~ Monotonous sequence af shale and!::2 BOLlNr' IAN ~ sandstone. Subdivision based on bio- ~, stratigraphic evidence (graptolites), C BfNDIGONIAN ~ not on litholo9y. ~ YAPEENIAN ~
28 l, 17 mcxsou eatenuemcore msrmcr LANCEFIELD msrmcr MELBOURNE WARRANDYTE-LILYDALE moon msrmcr warmu an msrmcr cave - LL ss CATHEDRAL sans L Eusuu BELL POINT LS C/I/2 Z Z: undifferentiated Q LIPTRAP g._ FORMATION < TABLE 2. Correlation of Silurian - Lower Devonian formations of the Melbourne district. 7 WW // > NORTON GULLY WARATAH ig Lllydll Lmmm SANDSTONE E LIMESTONE / 5 - s,ege, ' WILSON CREEK SHALE é HIUMEVALE ETLOON sans 3 MT IDA BEDS S LTSTONE G LOCIIKDVIII -----i-- é 1 asnunnlnn E Z( P s1 Lu L v MCWOR SANDSTONE undnfferentsuted Q /covered nnterva Pmuolhuu A _ 9,/ f as wmmnn DARGILE FORMATION DARGILE f=0rma~f 0N // // C ' NT N i covered interval; / = 'ENLUCKMN WAPEN-TAKE FgRMA1' 0N / / / / I ANDERSON 5 FORMA-HON KEILOR GROUP F0$ `il; f0n Q SPRINGFIELD nh C _/I / U -» '/nm... amd# F R'AT' N E'- ;-3; wafmdvfe C N AOAN 1 LLAIIDUVERIAII COSTERFIELD s..t.,~. cn ', B 'H SANDSTONE SILTSTONE DEEp CREEK 1 SILTSTONE.mn A 7 7'/7 pt ~ - / not exposed 1? 'not pxposed Z / / / A 4/mr fm n the formation at Cottles Bridge (D. E. Thomas and P. R. Kenley,pers. comm. ). Thomastus jutsoni, found near Templestowe, is closely comparable to Thomastus from the 1llaenus' band at Heathcote. The widely distributed Dargile Formation follows (Yan Yean Formation, Williams, 1964; Christmas Hills Formation, Gill, 1965), and is 1700 m thick in the Ringwood area (VandenBerg, 1971). East of Melbourne it is relatively uniform, comprising thin to medium interbedded flysch-type sandstones, siltstones, and rare shales. The sandstones typically show current bedding, and often have planar lamination. _North of Melbourne, in the Wandong district, Williams (1964) has recognised two members, the lower being about 600 m thick, and similar to the Ringwood sequence. The upper member, about 900 m thick, consists of rhythmically bedded siltstones with interbedded thin sandstones, whereas at Heathcote these lithologies are dominant throughout the formation. The Dargile Formation is noted for the presence of echinoderms. In the Melbourne area, a rich ophiuroid-asteroid-crinoid fauna is known from the type Melbournian' locality at Moonee Ponds Creek, Brunswick, and from South Yarra (Talent, 1967). The fauna also includes brachiopods, bivalves, and trilobites. A monograptid fauna from Studley Park includes Monograptus chimaera and 'Monograptus crinitus (probably belonging to the Lobograptus scanicus group) (Jones, 1927). Thomas and Keble (1933) record, amongst others, 'Monograptus' chimaera, M. bohemicus and M.' nillsoni from various localities around Melbourne. In addition, Thomas and Kenley (pers. comm.) have found Monograptus' chimaera and Lobograptus scanicus from Wonga Park at or just below the base of the Dargile Formation (Garratt, 1973 b ), and 'Monograptus' bohemicus from near Cottles Bridge and further east at One Tree Hill. Although these faunas need to be re-studied, they indicate a Lower Ludlovian age for the graptolite beds. spp.
29 18 Thick siltstones with thin interbedded sandstones outcrop on the eastern flank of the Mornington Peninsula Antiglinorium (Keble, 1950). Recognisable Silurian graptolites have only been found in the northern part, and are thought to correlate with the Anderson Creek Formation. Lower Devonian. The Humevale Siltstone (Ruddock Siltstone, Gill, 1965), outcrops in the Lilydale Syncline in the eastern part of the area. lt consists of about 4, 300 m of massive to thinly bedded siltstones with very thin interbedded sandstones. As the basal part is unfossiliferous, the age of the Dargile-Humevale boundary is poorly known: Talent (1965) places it for convenience near the Siluro-Devonian boundary (Table Z). The upper part of the formation is richly fossiliferous in places (see Ch. 4), including the Lilydale Limestone Lens which occurs near the exposed top of the formation. Talent (l965; and in Talent and Banks, 1967) assigned this limestone to the Emsian, largely on unpublished studies of the brachiopod fauna. Philip and Pedder (1967) gave a Lower Siegenian age for the limestone, based on the coral and conodont fauna. Revision of the conodont fauna points to a Middle to Upper Siegenian age (Cooper, 1970). At Lilydale the Cave Hill Sandstone overlies the Lilydale Limestone Lens unconformably. This is a sequence of white, finelylaminated silty sandstones and pebbly sandstones of marine origin, which may possibly correlate with the basal marine part of the Cathedral Beds near Taggerty. The Cave Hill Sandstone marks the close of geosynclinal deposition in the Melbourne district. LATE MIDDLE DEvoN1AN DEFoRMAT1oN. The Lower Palaeozoic sediments were folded during the late Middle Devonian Tabberabberan Orogeny'. The resulting structural pattern is one of major anticlinoria and synclinoria, showing a remarkably uniform axial strike in the Melbourne district of about 0300 (Fig. 2). Tight folding is restricted to the Ordovician and Lower to Middle Silurian rocks, whereas the Upper Silurian and Lower Devonian rocks generally occupy wide, fairly open synclines. Folding of the Upper Silurian sediments in the Melbourne Synclinorium (the southern extension of the Merriang Syncline) is confused; fold axes are poorly defined and discontinuous, and wide belts of sediments have low angles of dip. In the Melbourne district, three major strike faults, all with large easterly downthrow, are present. Along the Djerriwarrh Fault, part of the Castlemainian, the entire Yapeenian, and part of the Darriwilian are absent. The Moormbool Fault, largely hidden by Cainozoic basalt, marks the boundary between steeply dipping Middle Silurian and gently folded Upper Silurian sediments (N.W, Schleiger, pers. comm. ). The Yarra Fault separates the westerly dipping Dargile Formation from the easterly dipping Humevale Siltstone. (Garratt, l973a). UPPER DEVONIAN Mount Dandenong Volcanics. Following the Tabberabberan folding, acid volcanics were extruded in several parts of Victoria, and at Mount Dandenong the sequence has been subdivided into four formations (Morris, 1914; Edwards, 1956; VandenBerg, 1971; see Ch. 5), as follows: Ferny Creek Rhyodacite - 'Upper Dacite' Kalorama Rhyodacite -_ 'Middle Dacite' Mt. Evelyn Rhyodacite - 'Lower Dacite' Coldstream Rhyolite - Lower' and 'Upper Toscanites These occur in a triangular cauldron collapse structure, bordered to the south by a fault, and to the west and east by faults and homoclinal warps. A thick acid dyke along the prominent Yellingbo Fault may have been a feeder.
30 Acid lntrusions. 19 A number of granodiorite intrusions occur in the Melbourne district. The largest of these, the Lysterfield Granodiorite, intrudes Silurian-Devonian sediments and the Mount Dandenong Volcanics. lt is a medium-grained biotite granodiorite, with some hornblende (Edwards, 1956) lts metamorphic aureole is up to Z km wide in the Silurian-Devonian sediments, and includes schistose rhyodacite at the contact with the Ferny Creek Rhyodacite. Similar metamorphism of the sediments flanking the Mount Dandenong Volcanics on the east and west suggests hidden intrusions. In the Yarra Glen - Tarrawarra area, Garratt (1973 a ) has discovered a fault system comprising the NW-SE Tarrawarra Fault, with a southerly downthrow, and the Tarrawarra Ring Fault, along which some rotational movement has taken place. The entire fault complex has been intruded by acid dykes. lt is not known whether this faulting took place during the Tabberabberan 'Orogeny', or accompanied the somewhat younger Dandenong Ranges cauldron subsidence. The Bulla Granodiorite is largely covered by Cainozoic basalts. lt is a medium to coarse grained biotite granodiorite, sometimes approaching adamellite (James, 1920; Stillwell, 1911; Tattam, 1925). Both granitic and hornfelsic xenoliths are abundant and the hornfels aureole is rather narrow (370 to 800 m wide). A small isolated area of hornfels on Deep Creek about 3. 5 km north of Bulla indicates granodiorite at shallow depth. The very small, partly covered Morang Granodiorite is medium to fine grained and contains biotite and minor hornblende (Edwards and Baker, 1944). It has a narrow marginal phase with large orthoclase phenocrysts in a contaminated granodiorite groundmass, and is surrounded and partly covered by a hornfels aureole. Small granitic intrusions are also known from St. and near Silvan. Kilda, South Yarra, near Huntingdale, Kaolinisation of the granodiorite at Broadmeadows and Bulla (Bulla Granodiorite), at Dandenong (Lysterfield Granodiorite), and at South Yarra, may be due to Tertiary weathering. Kaolin-rich late Tertiary sediments overlie the Bulla Granodiorite, and form thick deposits in the Campbellfield area. Numerous quartz-bearing dykes intruding the Lower Palaeozoic are nearly always weathered to clay. They are probably contemporaneous with the granitic intrusions. A swarm of feldspar-hornblende porphyry dykes has intruded the Lysterfield Granodiorite and surrounding hornfels and rhyodacite, possibly following closely the intrusion of the granodiorite (Edwards, 1956). CAINOZOIC SEDIMENTS AND VOLCANICS. During the Cainozoic, the Port Phillip Sunkland developed as a basin of marine and non-marine sedimentation, and was also the site of periodic basaltic volcanic activity. The Sunkland is bounded by the Rowsley Fault and the Selwyn Fault, with the upthrown Mornington Peninsula lying to the east (Fig._ 1). The northeastern limit of the Tertiary sea was controlled by the relatively minor Melbourne Warp, which extends from Dandenong to Essendon. North of this structure the sediments are essentially non-marine, whereas the thicker sequences to the south and west are partly marine and thicken basinwards. lts latest movement post-dates the Brighton Group near Dandenong. The formations are generally flat, commonly dipping at -Q50 to lo, and lie unconformably on Silurian (and Ordovician) sedimentary rocks and on granitic rocks. On the Mornington Peninsula the Tertiary sediments on the upthrown side of Selwyn Fault are relatively thin, although thick Lower Tertiary Older Volcanics cover much of the southern part of the upthrown block. West of Selwyn Fault the sequence is incompletely known, but is much thicker. For example the Nepean No. Z9 Bore drilled to 615 m without penetrating beyond the Middle Tertiary (Longfordian), and large thicknesses in the nearby Sorrento Bore included
31 m of Quaternary sediments. This indicates fault movement of over 600 m during the Cainozoic. In general, three main phases of deposition can be distinguished in the Melbourne district: 1. Early Tertiary terrestrial deposition, Z. Middle Tertiary marine deposition, 3. Late Tertiary terrestrial deposition. Intermittent volcanic activity occurred in each phase. 1. Early Tertiary Phase. (a) Werribee Formation. The Werribee Formation is known only from bores and unconformably overlies Ordovician and Silurian sediments. It is widespread southwest of Melbourne and has been encountered in the southeastern suburbs, south of the Beaurnaris Monocline. At Bacchus Marsh, its equivalent is the Yaloak Formation (Thomas and Baragwanath, 1950). The formation consists of coarse to fine, pyritic, angular sands and silty sands, with at least two main lignite seams. Minor clays, ligneous clays and occasional lenses of gravel occur. Basalts (Older Volcanics) occur at or near the top. The formation reaches a maximum thickness of about 110 m in the Werribee area. Kenley (1967) suggested a partly paludal, partly estuarine depositional environment, although fluviatile elements may be present. Stratigraphically useful fossils are absent. Cookson (1959) identified several species of Nothofagus pollen from the Altona Coal Seam, and suggested an Eocene to Early Miocene age, but foraminifera in the overlying Newport Formation set the upper age limit at Late Oligocene (C. Abele, pers. comm. ). (b) Undifferentiated Sub-Older Volcanic Sediments. Scattered and thin Early Tertiary occurrences of sandy gravel, sand, silt and clay underlie the Older Volcanics at numerous localities. These represent alluvial valley fills which have been protected by the overlying basalts. Poorly sorted sands and gravelly sands are widespread in the Kangaroo Ground - Greensborough area. Sandy silts and sands containing kaolin, probably derived from the Bulla Granodiorite, occur at Campbellfield, and isolated lenses of sandy silt and clay ('leaf beds') occur along Moonee Ponds Creek. The flora includes Ficonium nitidum, Eucalyptus kitsoni, Nothofagus muelleri, and Cinnamomum~ sp. (Paterson, 1934; Douglas, 1967). (c) Older Volcanics. In the Melbourne district the Older Volcanics occur in three discrete areas: Tullamarine-Gampbellfield-South Melbourne; Bundoora-Greensborough- Kangaroo Ground; and in the Woori Yallock Basin, east of the Dandenong Ranges. In the latter two areas, they occur as residual hill cappings, whereas the westernmost basalts are overlain by or interbedded with Tertiary sediments. The most extensive occurrence is found on the Mornington Peninsula, being up to 600 m thick. The Older Volcanics 'comprise two groups (Edwards, 1938) distinguished respectively by ophitic titanaugite, or nontitaniferous granular augite in the groundmass. Edward's Moorooduc type of olivine titanaugite basalt occurs from Greensborough to Kangaroo Ground, as well as in the Mornington Peninsula. Analcite-bearing types (crinanites and crinanite basalts) are less common. Of the olivine basalts without titanaugite, the Flinders type is widespread, and is characterised by a considerable amount of green glass, generally devitrified. The finer-grained Keilor type, with abundant brown glass, occurs particularly in the Essendon-Keilor area, and has close, well-developed jointing in the Tullamarine Quarries. The intercalated basalts in the Werribee Formation are regarded as Eocene to Oligocene. Recent radiometric age determinations (Geol. Surv. Vic.) show that the Tullamarine and Greensborough basalts are considerably younger, being comparable in age with the Miocene Maude Basalt (Bowler, 1963).
32 ~ TABLE 3. Generalised stratigraphy and correlation of the Cainozoic of the Melbourne district. Time-scale is not drawn to the scale of dates shown (from Berggren, 1972). MELBOURNE DISTRI.CT MORNINGTON GEELONG RECENT PLEISTOCENE l.8my Port Melbourne Sand Yarra~I Coo de Island Silt Delta I Newer Volcanics O.8my G roup Fishermans Bend Silt ~. Moray Street Gravels UPLIFT FOLLOWED BY EROSION. [ Deposition in Yarra Delta [& other areas] Periodic volcanic activity. PLIOCENE 5my Kalimnan LatejCheltenhamian lomy Hi tchellian TERRESTRIAL. - mainly fluviatile. SHALLOW MARINE. - regressive. Terrestrial north of Melbourne Wa NON-DEPOSITION. -? marine erosion. 7- Baxter Sandstone Newer Volcanics Moorabool Viaduct Sands Nodule Bed MIOCENE I 22. 5my MiddleJBairnsdalian 16my Balcombian EarlYIBatesford~an ILongfordian MARINE. Newport Formation - main transgression'll rs including some 8atesford< limestones. Tullamarine and Greensborough Basalts I Some volcanic activity. OLIGOCENE Janjukian EROSION / NON-DEPOSITION. 38my TERRESTRIAL (with minor shallow marine, estuarine, swamps, etc.l EOCENE Periodic volcanic activity. N
33 22 Basic dykes, known fro:m :many parts of the district, :may be related to the Older Volcanics. They include alkaline dykes (Hills, 1941), la:mprophyre dykes (Edwards, 1934) and a li:mburgite plug (Chap:man and Thiele, 1911) and are :mostly weathered to clay. 2. Middle Tertiary Marine Phase. (a) Newport For:mation (Newport Silt). Marine sedi:ments of Oligocene age are known fro:m the base of the Newport For:mation (Abele, pers. co:m:m.). In the Miocene, :marine conditions beca:me :more extensive, resulting in the for:rnation being deposited disconfor:mably on the Werribee For:mation, and overlapping on to the bedrock. The typical fresh lithology is known only fro:m sub-surface occurrences and co:mprises grey and green glauconitic clayey silts. So:me thin i:mpure lignites and carbonaceous silts occur near the base. Sandy and calcareous littoral to shallow:marine sedi:ments were deposited near the basin :margin as an extensive sheet, of which only re:rnnants are preserved. The for:mation is widespread in the southern part of the district, reaching a :maxi:mu:rn thickness of about 120 :m in the Werribee area where it beco:mes increasingly sandy westwards, in the proxi:mity of the You Yangs. Southeast of Melbourne the for:mation is up to 60 :m thick south of the Beau:rnaris Monocline, but is :much thinner to the north. Minor pockets of i:mpure bryozoa.lli:mestone are found near the base. In the vicinity of Melbourne, re:rnnants of the littoral deposits are found in railway cuttings at Windsor, South Yarra, South Melbourne, Royal Park and Essendon, and also along the Maribyrnong River downstrea:m fro:m Keilor (including the Green Gully Li:mestone). In tunnels in the Gardenvale-Or:mond district, littoral deposits lie on a rocky coastline cut into the Silurian bedrock in the Miocene. The rich fauna of the Newport For:mation includes :molluscs, corals, brachiopods, fora:minifera, echinoder:ms and sponge spicules (Abele, pen. co:rn:rn.; Darragh and Abele, in VandenBerg, 1971; Kenley, 1967, lists earlier references). Fora:minifera show that it ranges fro:m Early to Late Miocene (Batesfordian to Bairnsdalian) southeast of Melbourne and fro:mlate Oligocene to Middle Miocene (Longfordian to at least Balco:mbian) to the west. Beyond the Melbourne district, extensions of the for:mation include the Fyansford Clay (Geelong), Balco:mbe Clay (Mornington) and the Sherwood Marl (Westernport area). (b) Brighton Group. This unit for:ms an extensive cover over the southern and south-eastern suburbs, whereas west and southwest of the city it is below sea level and often thin or even absent. It disconfor:mably overlies the Newport For:mation, or unconfor:mably overlies the Older Volcanics and Palaeozoic rocks, and co:mprises two for:mations - the predo:minantly :marine Black Rock Sandstone, and the overlying terrestrial Red Bluff Sands. Marine Brighton Group sedi:ments are essentially confined to the region southwest of the Melbourne Warp. Residual cappings of ferruginous clayey sands and gravels northeast of the Warp are probably largely Red Bluff Sands and :may possibly be equivalent in part to the Black Rock Sandstone. The Black Rock Sandstone is known fro:m Essendon to the!louth-eastern suburbs. At the type locality at Beau:rnaris it consists of about 15 :m of ferruginous sandstones and silty or rarely pebbly sands, disconfor:mably overlying the Newport For:mation. A thin nodule bed containing phosphatic concretions and abraded vertebrate re:mains (sharks' teeth, whale, penguin and albatross bones)represents a significant ti:me gap between the two for:matiuns. The richly fossiliferous basal 6 :m at Beau:rnaris is the type locality of the Cheltenha:mian (upper:most Miocene). In bores, the for:mation consists of glauconitic, silty and shelly sands, and is difficult to distinguish lithologically fro:m the underlying Newport For:mation. A rich :molluscan fauna includes littoral and sub-littoral species fro:m several localities, and indicates that deposition occurred in progressively shallowing water (Darragh, in VandenBerg, 1971). The for:mation can be correlated with the lower (:marine) part of the Mciorabool
34 ~ ~_5W NE 1 OLDER VOLCANICS (Greensborough Phase) NEWER VOLCANICS v V V V v BRIGHTON GROUP Granite '_'~..:',::';';..o-~;::::...;:.~'.:.;;::':'::':~ 100- ' ///:/:///'i/:;::::;:00_~;:::>/;:::;;:?:;3;-~/::;:;::;:;:::/~;;:~::::~~/;:::c~~:;::~;-~~%--%m ///.// _/: / _/././';-;::..--: :/./;_:0-/;/; /;::::;::;//;0~-:;> ~::./;:::-C:-% ~ :/ ~~-~~ _~~/;:::? /.// y'--;:--.--c. - /'~ - =~ ~/..--:::-:%/_/ /;/./ met /.--;:--///~~~-_~»;:;;/.--c. //;::;:.:- ;:-: /~~ metre. Fig. 3 (upper). Melbourne area. Fig. 4 (lower). Diagrammatic cross-section illustrating the stratigraphic relationships of the principal Tertiary formations in (Not to scale, vertical dimension greatly exaggerated. adapted from Kenle~ 1967). Cross-section of the Yarra Delta between Stony Creek, Spotswood and Princes Bridge (after Neilson, 1967). the N W
35 24 Viaduct Sands at Geelong (Ch. 7), possibly also with the littoral Marina Cove Sand at Mornington (Ch. 6). 3. Late Tertiary Terrestrial Phase. (a) Brighton Group - Red Bluff Sands. The Red Bluff Sands outcrop in a wide area between Essendon, Camberwell, Dandenong and the coastline, and extend under the New Volcanics southwest of Melbourne. Gill (1950, 1958) suggested a disconformity between it and the underlying Black Rock Sandstone, possibly with an intervening period of laterisation. The formation is 24 m thick at the type locality near Sandringham, but is somewhat thicker in the Ormond-Oakleigh area. It consists of poorly consolidated sands, silts, clays and gravels, often with cross-bedding and rapid changes of grain size. Individual bands have been ferruginised by weathering. Gill (1957) postulated a partly fluviatile, partly nearshore lagoonal or paludal origin for the formation. However, a predominantly fluviatile environment is likely. The sparse fauna and flora includes a fresh-water spong spicules and bivalves, wood fragments, and pollen. An acritarch (Hystrichosphaeridium tubuliferum; Gill, 1957) from Red Bluff is indicative of a marine environment, although the associated remaining flora is terrestrial. The Red Bluff Sands are probably of Middle to Late Pliocene age (Singleton, 1941). In the Geelong area, its equivalent is represented by the upper part of the Moorabool Viaduct Sands, and on the Mornington Peninsula it is represented by the Baxter Sandstone. Undifferentiated thin, discontinuous deposits of fluviatile silty sand and sandy gravel, often partly silicified, underlie the Newer Volcanics northwest of Melbourne. These become more continuous southwards and merge laterally into the Red Bluff Sands. Near Bulla, they contain Eucalyptus spp., Acacia spp., and ferns. The deposits are regarded as Pliocene, although definite indication of their age has yet to be found. (b) Newer Volcanics. Erosion of the Red Bluff Sands and underlying rocks produced only slight relief southwest and east of Melbourne. Subsequent volcanicity formed the Werribee Plains - a continuous sheet of Newer Volcanics up to 60+ m thick. In contrast, the volcanics were restricted to valley flows in the undulating topography fringing the Werribee Plains. The Newer Volcanics have been extruded from a large number of basalt and scoria cones, and comprise numerous flows, with interbedded pyroclastics, sand, and soil horizons. Most of the flows in the district are olivine basalts of various types, but limburgites are also known (Edwards, 1938; Condon, 1951; Hanks, 1955). A range of more siliceous alkaline variants occurs in the Gisborne-Macedon district (Ch. 11). Condon (1951) suggested two phases of activity in the Werribee Plains, early extensive sheet flows of olivine and pyroxene basalt, possibly from dyke feeders, and later small tongue flows of olivine and iddingsite basalt from central vents. As many of the flow boundaries, however, are not visible on aerial photographs, and others are traceable only for short distances, this interpretation is uncertain, particularly as the sequence north of Melbourne does not show any clear division into earlier sheet flows and later central eruptions (Hanks, 1955). In this area the youngest flow (possibly the youngest in the entire district) extends probably from Mt. Fraser to the Yarra Delta, a distance of 50 km. The Pliocene-Pleistocene age of the basalts has been confirmed by radiometric dating (Page, 1968). The oldest dated basalt is from the Essendon area, with an age of 4.5 m. y.. Basalts from Newport and Albion gave dates of 2. 5 m. y., and a basalt from Northcote, probably originating from one of the vents near Craigieburn, gave an age of 2.2 m. y.. The Mt. Fraser-Yarra Delta flow has been dated at Alphington at 0.81 m. y.. Most of the numerous volcanic cones in the district are of the flat-topped type (see page 97), for example Mt. Kororoit. A variety of scoria cones occurs, for example Mt. Fraser, with multiple deep craters and relatively steep slopes, and Mt. Mary with a low breached cone. j The Newer Basalts show a variety of well-preserved structures. The basalts are typically vesicular, for example, on shore platforms south of Williamstown, where vesicles are arranged along confused flow lines. Columnar jointing is widespread, unusual examples of which along Jacksons Creek include the well-known Organ Pipes. Pillow lavas occur at the base of flows at Exford (Condon, 1951) and Footscray. A fine example of a radial squeeze-up rising some 5 m occurs on Mt. Kororoit. On the Mt. Fraser flow east of Merri Creek, in the Beveridge Donnybrook area, crescentic tumuli are well developed,and unusual, broad flat-topped stony rises lie above the general level of the basalt..
36 25 QUATERNARY Thin Quaternary sediments are scattered throughout the district and include alluvial, swamp, deltaic, fault apron and dune deposits. The Darley Gravels and Werribee flood plain deposits consist of sediments eroded from the upthrown blocks of the Rowsley and Coimadai Faults. The Darley Gravels grade from fault apron sandy silts, sands and gravels to alluvial sandy gravels along the Werribee River and Toolern Creek. The Werribee flood plain consists of poorly bedded, well sorted overbank silts with minor sand interbedded in the lower part. Three Pleistocene stream courses are still traceable on the surface of the flood plain. Thin (not more than 1 m) wind-blown silts 'and sandy silts, probably derived from these Quaternary sediments, form a veneer over the Newer Volcanics'extending eastwards into the western suburbs. Pliocene or Pleistocene rejuvenation of the Yarra Fault developed aggrading conditions in the Yarra River between Yarra Glen and Healesville with consequent formation of an extensive flood plain. The high-level alluvium along the Yarra River downstream from Templestowe, and along Gardiners Creek, was deposited following damming of the lower reaches of the Yarra by the Mt. Fraser - Yarra Delta flow. Younger low-level alluvium was deposited following the cutting of a new stream course. In the Yarra Delta, sedimentation occurred in a deep, broad drowned valley system, cut into Pliocene basalts and older rocks (Neilson and Jenkin, 1967). The maximum vertical thickness of sediment in depressions and channels is about 45 m, but usually is little more than 30 m and may be as little as 8 m. The development of the delta reflects fluctuating Quaternary sea levels, and includes one major break in deposition. The earliest deposition was of widespread fluviatile gravels and sands (Moray Street Gravels), probably during a glacial low sea level. Marine deposition during an interglacial period of high sea level produced the overlying silty clays and clays of the Fishermens Bend Silt, following which a succeeding low sea level caused a major break in deposition, with sub-aerial exposure indicated by the over-consolidation, oxidation and fissuring of the silty clays. During this break, lava from Mt. Fraser (0.81 m. y.) flowed down the valley as far as the Yarra Delta. A return to marine-estuarine conditions is shown by the soft, dark grey silts and clays of the Coode Island Silt, lying disconformably on the Fishermens Bend Silt, and on the basalt flow {.seen inbores at Jolimont). A radiocarbon date on tree material within the Coode Island Silt of approximately 8500 years, gives an estimate of the age of this interglacial high sea level. The uppermost unit is the Port Melbourne Sand, from 20 ft. to 40 ft. thick, consisting of medium to fine, littoral to near-shore sands containing shell beds, on the surface of which sand ridges were developed. Present sea level is approximately 1 m below the topmost marine sands, indicating the extent of the retreat of sea level since Coode Island Silt time. The Carrum Swamp comprises a thin sequence of black clays and silts and minor shell beds, probably of Pleistocene age, reflecting a swampy lagoonal environment with minor marine inte rcalations. PHYSIOGRAPHIC EVOLUTION The physiographic evolution of the Melbourne district was governed by combinations of erosion, faulting, warping and volcanic activity. West of Melbourne, the topography has low relief and is determined by the late Cainozoic volcanicity and by faulting. In contrast, east of Melbourne, extensive areas of outcropping bedrock have higher elevations. Prolonged erosion has produced a step-like succession of partially preserved erosion surfaces, dissection of which has resulted in considerable relief. Topographic effects of Cainozoic faulting are also apparent. Areas east of Melbourne. Three main cycles of erosion are recognisable in central Victoria, culminating in turn in the Baw Baw Surface, the KinglakE' Surface and the Nillumbik Terrain. Late- Tertiary
37 26 uplift (Kosciusko Uplift) initiated further dissection. The Baw Baw Surface (considered either Cretaceous or Triassic by Hills, 1934, 1955) is the oldest recognisable feature and is only preserved in resistant rock types, for exanlple, around Mt. Baw Baw (1500 Ill), Mt. Torbreck (1500 Ill) to Mt. Donna Buang (1200 Ill) and possibly Mt. Macedon (1000 Ill). The Kinglake Surface (the Triassic Erosion Surface of Neilson, 1970; but possibly up to Early Tertiary in age) is represented by two extensive plateaux. The higher Gregory Plateau (ranging froill 900 to 1200 Ill) slopes gently westward froill the Matlock district to Toolangi and GeIllbrook, possibly with Mt. DisappointIllent as an outlying reinnant, and is flanked by the slightly lower Kinglake Plateau (500 to. 600 Ill) of the Kinglake - Flowerdale - Trawool district, with outlying reinnants in the Dandenong Ranges (600 Ill) and the Warranlate Hills (400 Ill) (Garratt, 1973a). The NillUIllbik Terrain is the proillinent erosion surface shown by the generally concordant level of ridges in the area of Silurian-Lower Devonian bedrock east and northeast of Melbourne. It rises in elevation froill about 20 III at Melbourne to about 200 III at the foot of Mt. Sugarloaf, which is part of the well-defined escarpillent at the southern edge of the higher Kinglake Plateau. It is also present further east in the 'Woori Yallock Basin (p. lsi). The NilluIllbik Terrain has been dissected by the Yarra River and its tributaries and to a lesser extent by the Dandenong Creek. North and west of the Dandenong Ranges, extensive flats along the Yarra Valley, and the broad valley of Olinda Creek-Dandenong Creek, together forill a belt of low elevation separated by scarps froill the higher NilluIllbik Terrain to the west. ' The Yarra Fault has been shown to be a Illajor structure with a total easterly downthrow of 1500 III (Garratt, 1973 a ) rather than an erosional scarp (Keble, 1915; Hills, 1934). Renewed IlloveIllent in the? Pleistocene produced the present fault scarp in the Yarra Glen district with a relief of about 240 Ill. As suggested by Jutson (1911a), IlloveIllent was slow enough for the Yarra to Illaintain its course through the upthrown block by excavating the deep Yarra and Yering Gorges. Extensive developillent of alluvial flats occurred upstreaill. The lowlands of the Olinda Creek-Dandenong Creek,valleys and the strike-ridge scarps to the west have been attributed to either differential erosion or to faulting. Between Glen Waverley and Dandenong, the Wheelers Hill Fault has prod'l1ced a proillinent scarp, whose IllaxiIllUIll relief of 100 III is partly due to subsequent erosion by Dandenong Creek. Pliocene Red Bluff Sands cap the Wheelers Hill Scarp and extend across the line of the Dandenong Valley with a relatively flat base, suggesting that there was no Illajor valley in the Pliocene. In the dissected area east of Melbourne, Tertiary sediillents occur only as residual hill cappings, but to tile southeast they forill the continuous low relief Brighton Coastal Plain (Neilson, 1967). The ill-defined drainage pattern of the coastal plain is largely deterillined by a series of distinct parallel low ridges trending NW, the Illain streaill being Elster Creek (Elwood Canal). The ridges are parallel to the coastline and have been variously referred to as dunes (Whincup, 1944), as folds in the Black Rock Sandstone (Kenley, 1967) or as structures akin to beach ridges within the Black Rock Sandstone (Kenley, in VandenBerg, 1971). They are absent east 'of the Melbourne Warp. Area west of Melbourne - Newer Volcanic Plains. The Newer Volcanic Plains are divisible into two physiographic entities, firstly, the Werribee Plains, entirely covered by Newer Volcanics or post-volcanic sediillents, and., secondly, a wide outer zone of Newer Volcanics covering an undulating terrain of Palaeozoic bedrock which frequently protrudes. J The plain has a gently coastward gradient of 0.5% to 0.8% and is silloothly undulating. In the outer zone, undulations often Illark the boundaries of flows (e. g. as on MMBW 1 :24,000 contour Illaps of the Bulla-MicklehaIll-Kalkallo area) but Illay also be found within flows. The strongly Illeandrine courses of the larger streanls reflect the gentle initial slope of the terrain. Subsequent entrenchillent has produced deep gorge-like valleys with
38 Nillumbik Terrain Kinglake Surface Baw Baw Surface Volcanic cones contour interval 100 metres miles a 5 ~ ~ I o 0 o W kilometres,tifmv {)u.'11 v'~<:o ','< ~«,<;;... ~<l' Kellor PORT PHILLIP BAY o /MELBOURNE Fig. 5. Morphometric map of south central Victoria, showing the distribution of the three main erosion surfaces. These surfaces are difficult to recognize in the western part of the area because of the extensive basalt cover. N -.J
39 28 steep sides partly due to columnar jointing. Jointing and abundant vesicles Inake the basalts highly perineable, and hence surface drainage is poorly dev.eloped. This has, to a large extent, prevented the norinal developinent of tributaries, the larger streains (Werribee River, Djerriwarrh Creek, Deep Creek, Jackson Creek) receiving Inuch of their water froin catchinents outside the volcanic plains. Many of the streains are lateral, flowing either along bedrock-basalt boundaries (e. g. Jackson Creek near Sunbury, Deep Creek upstreain froin Bulla, Plenty River upstreain froin Greensborough, and the Yarra River downstreain froin Studley Park) or along proininent flow boundaries (e. g. Merri Creek, EInU Creek, and part of the Werribee River). j Coastline The coastline of Port Phillip in the Melbourne district is partly erosional and partly depositional. In general the eastern coastline is exposed to Inore active erosion than the western. Deposition by the Yarra River, the Moonee Ponds Creek and the Maribyrnong River has built the Yarra Delta. North-westerly longshore drift with deposition of the youngest littoral sands of the delta (Port Melbourne Sands) has caused the Yarra below the confluence with the Maribyrnong River to flow along the eastern, cliffed Inargin of the Newer Volcanics, froin Footscray to WilliaInstown. The top of the Port Melbourne Sand which now lies about 1 In above sea level, originally showed surface sand ridges which have been obliterated by =an. FroIn St. Kilda to Mordialloc, the coastline is largely erosional The coastline is developed along the =argin of the coastal plain in Brighton Group sediinents, and headlands (Point OrInond, Green Point, Picnic Point and Rickett's Point) occur where gentle anticlinal warping has brought the relatively resistant Black Rock Sandstone to sea level. Intervening bays have been eroded into the softer overlying Red Bluff Sands. At BeaUInaris the coastline changes direction abruptly to north-easterly for about one Inile, along the strike of the axis of the BeaUInaris Monocline. This reflects a bedrock fault along which repeated InoveInent is shown by a total displaceinent of about 60 In, but displaceinent of the top of the Newport ForInation of only about 18 In. Moderately steep dips can be seen just offshore in the Black Rock Sandstone along the axis, and erosion of relatively flat-lying beds on the upthrown side has caused the BeaUInaris cliffs. On the downthrown side, the Red Bluff Sands have been brought down to sea level and their erosion has produced the pronounced bight between BeaUInaris and Mordialloc. South of Mordialloc, the Tertiary sediinents extend beneath the low-lying area of the CarrUIn SwaInp, which is bounded on the s.outheast by the Selwyn Fault whose scarp runs inland near Frankston. The swainp is bounded along the coastline by a zone of coastal dunes running froin Mordialloc to Frankston. The lower reaches of Kananook Creek are confined by these ridges froin CarrUIn to Frankston. West of Melbourne, the coastline is generally flat and of low elevation along the Inargin of the volcanic plain. Drainage is largely inhibited by low beach ridges, resulting in salt Inarsh and mangrove, which were forinerly Inore extensive. Deposition by the Werribee River has produced a large sub-aerial'delta', and =arine erosion of the soft Pleistocene (and Tertiary) sediinents has forined cliffs. A variety of evidence around the coastline points to a relatively recent fall in sea level. This includes the raised Inarine deposits of Anthony's Nose (DroInana), CarrUIn SwaInp, and the Yarra Delta, the shell beds at Altona, and also the raised shore piatiorin and fossil cliff behind Rickett's Point.
40 29 REFERENCES Berggren, W.A., A Cenozoic time-scale - some implications for regional geology and paleobiogeography. Lethaia, 5: Bowler, J. M., Tertiary stratigraphy and sedimentation in the Geelong-Maude area, Victoria. Proc. Roy. Soc. Vict., 76: Chapman, F., and Thiele, E. 0., On a limburgite rock occurring as a volcanic plug at Balwyn, near Doncaster. Proc. Roy. Soc. Vict., 24: Condon, M.A., The geology of the lower Werribee River, Victoria. Proc. Roy. Soc. Vict., 63: Cookson, I. C., Fossil pollen grains of Nothofagus from Australia. Proc. Roy. Soc. Vict., 71: Cooper, B. J., Lower Devonian conodonts at Lilydale and Loyola. Unpubl. B. Sc. (Hons.) Thesis, Univ. Melb. Douglas, J. G., Fossil Plants in Melbourne area, in Geology of the Melbourne District. Victoria. Geol. Surv. Vict. BuU:- 59: Edwards, A. B., Tertiary dykes and volcanic necks of South Gippsland, Victoria. Proc. Roy. Soc. Vict., 47: Edwards, A. B., Petrology of the Older Volcanic rocks of Victoria. Proc. Roy. Soc. Vict., 51: Edwards, A. B:-:-I956. The rhyolite-dacite-granodiorite association of the Dandenong Ranges. Proc. Roy. Soc. Vict., 68: Edwards, A. B., and Baker, G., Contact phenomena in the Morang Hills, Victoria. Proc. Roy. Soc. Vict., 56: Garrett, M. J., 1973a. Faulting and physiography of Croydon Sunkland. Proc. Roy. Soc. Vict., (in press). Garrett, M.J.,1973b. Explanatory notes to the Yan Yean and Kinglake 1:63,360 geological maps. Mines Dept. Vict. Geol. Surv. Rept., (in press). Garrett, M.J., et. ai., Yan Yean 1:63,360 geological map. Mines Dept. Vict. (in press). Geological Survey of Victoria, Melbourne. 1:250,000 geological map. Mines Dept. Vict. Geological Survey of Victoria, Queenscliff 1 :250,000 geological map. Mines Dept. Vi ct. Gill, E.D., Nomenclature of certain Tertiary sediments near Melbourne. Proc. Roy. Soc. Vict., 62: Gill, E.D., On the age of the bedrock between Melbourne and Lilydale, Victoria. Vict. Nat., 69(4): Gill, E.D., The stratigraphical occurrence and palaeoecology of some Australian Tertiary marsupials. Mem. Nat. Mus. Vict., 21: Gill, E.D., Dating of Cainozoic non-marine rocks in Australia. ANZAAS Adelaide, Abstracts of lectures and papers. Gill, E.D., The Devonian rocks of Lilydale, Victoria. Vict. Nat., 82(4): Hanks, W., Newer Volcanic vents and lava fields between Wallan and Yuroke, Victoria. Proc. Roy. Soc. Vict., 67: Hills, E.S., Some fundamental concepts in Victorian physiography. Proc. Roy. Soc. Vict., 47: Hills, E.S., The Silurian rocks of the Studley Park district. Proc. Roy. Soc. Viet., 53: Hills, E.S., Physiography and geology, in Introducing Victoria, Ed. G. W. Leeper, pp (ANZAAS, Melbourne). Hills, E. S., The Physiography of Victoria. 4th ed. (Whitcombe and Toombs, Melbourne). Hills, E. S., and Thomas, D. E., Turbidity currents and the graptolitic facies in Victoria. J. Geo!. Soc. Aust., 1: James, A. V. G., The physiography and geology of the Bulla-Sydenham area. Proc. Roy, Soc. Vict., 32: Jones, O.A Silurian graptolites from Studley Park, Melbourne, Australia. Geo!. Mag., 64: Jutson, J. T., 1911a. A contribution to the physiography of the Yarra River and Dandenong Creek basins, Victoria. Proc. Roy. Soc. Vict., 23:
41 30 Jutson, J. T., 1911 b. The structure and general geology of the Warrandyte goldfield and adjacent country. Proc. Roy. Soc. Vict., 23: Keble, R. A., The significance of lava residuals in the development of the Western Port and Port Phillip drainage systems. Proc. Roy. Soc. Vict., 31: Keble, R. A., The Mornington Peninsula. Geo!. Surv. Vict. Mem. 17. Kenley, P. R., The Tertiary, in Geology of the Melbourne District, Victoria. Geo!. Surv. Vict. Bull~59: 30,:,46. Morris, M., On the geology and petrology of the district between Lilydale and Mount Dandenong. Proc. Roy. Soc. Vict., 26: Neilson, J.L., The physiography of the Melbourne area, in Geology of the Melbourne District, Victoria. Geol. Surv. Vict. Bull. 59: Neilson, J. L., Notes on weathering of the Silurian rocks of the Melbourne District. J. Inst. Eng. Aust., 42: 1-2, Neilson, J. L., and Jenkin, J. J., Quaternary, in Geology of the Melbourne District, Victoria. Geo!. Surv. Vict. Bull. 59: Page, R. W., Catalogue of radiometric age determinations carried out on Australian rocks in Bur. Min. Res. Geo!. Geophys. Rec. 1968/30: Paterson, H. T., Notes on some Tertiary leaves from Pascoe Vale. Proc. Roy. Soc. Vict., 46: Philip, G. M. and Pedder, A. E. H., Stratigraphical correlation of the principal limestone sequences of Eastern Australia. Int. Syrup. Dev. Syst., Calgary, Vol. 2: Singleton, F. A., The Tertiary geology of Australia. Proc. Roy. Soc. Vict., 53: Stillwell, F. L., Notes on the geology of Broadmeadows. Proc. Roy. Soc. Vict., 24: Strusz, D. L., et al Correlation of the Lower Devonian rocks of Australasia. J.' Geol. Soc. Aust., 18: Talent, J. A The stratigraphic and diastrophic evolution of central and eastern Victoria in Middle Palaeozoic times. Proc. Roy. Soc. Vict., 79: Talent, J. A., Silurian, sedimentary petrology and palaeontology, in Geology of the Melbourne District, Victoria. Geol. Surv. Vict. Bull. 59: Talent, J. A. and Banks, M. R., Devonian of Victoria and Tasmania. Int. Symp. Dev. Syst., Calgary, Vol. 2: Tattam, C. M Contact metamorphism in the Bulla area and some factors in differentiation of the granodiorite of Bulla, Victoria. Proc. Roy. Soc. 37: Thomas, D. E., and Baragwanath, W., Geology of the brown coals of Victoria, Pt. 3: Port Phillip Sunkland. Min. Geo!. J. Vict., 4(2): Thomas, D. E. and Keb1e, R. A., The Ordovician and Silurian rocks of the Bulla-Sunbury area, and discussion of the sequence of the Melbourne area. Proc. Roy. Soc. Vict., 45: VandenBerg, A.H.M., Explanatory notes on the Ringwood 1:63,360 geological map. Mines Dept. Vict. Geo!. Surv. Rept. 1971/1. VandenBerg, A. H. M., et~., Ringwood 1 :63,360 geological map. Mines Dept. Vict. VandenBerg, A. H. M., et a!. Melbourne and Sunbury 1:63,360 geological maps. Mines Dept:-Vict. (in press). VandenBerg, A.H.M., and Schleiger, N.W., Palaeogeographic and tectonic significance of diachronism in Siluro-Devonian age flysch sediments, Melbourne Trough, Southeastern Australia: Discussion. Geol. Soc. Amer. Bull. 83: 1565_1570. Whincup, S., Superficial sand deposits between Brighton and Frankston, Victoria. Proc. Roy. Soc. Vict., 56: Williams, G. M., The geology of the Kinglake district, Central Victoria. Proc. Roy. Soc. Vict., 77:
42 31 CHAPTER 3 QUATERNAR Y SEDIMENTS OF THE MARIBYRNONG RIVER, KEILOR by E. D. Gill The Maribyrnong River flows south and is incised through the basaltic plains of Upper Pliocene and Quaternary lavas, through the underlying Tertiary marine and nonmarine rocks, and into the Silurian and Ordovician bedrock. Its course is affected by old valleys it crosses. Thus at Keilor it crosses an Eocene or Oligocene valley infilled with Older Basalt, so that upstream the river has cut a broad valley. The Keilor cranium site is where Dry Creek joins the Maribyrnong River at the north end of this broad floodplain. Downstream from this Early Tertiary valley, the Maribyrnong River takes a wide sweep in the Silurian bedrock, flowing in a narrow valley with rapids. Near the downstream end of the rapids, Green Gully joins the Maribyrnong River near the site of the discovery in 1965 of Green Gully Man. River terraces may be considered as bodies of sediments (geologic formations) or planar surfaces (geomorphic features). The following terraces have been named: Youngest Oldest Planar Surface Maribyrnong Terrace Keilor Terrace Arundel Terrace Geologic Formation Maribyrnong Alluvium Doutta Galla Silt Arundel Formation In geologic nomenclature, the name Keilor had been used for a stage and so was not available here for a formation. The Arundel Formation contains materials of more than one age; they are in process of being differentiated. Some recognize an erosion surface between the Maribyrnong Terrace and the Keilor Terrace named the Braybrook Terrace. It is cut in the Doutta Galla Silt. The writer considers that in the Yarra Delta these formations interdigitate with marine formations. The Coode Island Silt (the top of which is mid-holocene) lies in a valley cut in the Doutta Galla Silt. Radiocarbon dates show that the Doutta Galla Silt began to be deposited before years B. P. and finished deposition after 8,500. Its age range may be of the order of to years B. P. Green Gully Man is in Doutta Galla Silt. The fossil age is of the order of years. Keilor Man is older. and in the same formation. but more difficult to date. A sample. too small for proper dating, at the level of the cranium at the cranium site gave a 14C age of 15,000 ± 2000 years. Carbonate from the Keilor cranium. which can only give a minimum date for the emplacement of this material, gave a date of 7360 years. This is a minimal limit on the age of the cranium. The Doutta Galla Silt. which contains the cranium, is graded not to present sea level, but to the low sea level of the last glaciation. The Doutta Galla Silt. in its upper ten feet or so, is of very even grain size and similar to a loess. It is considered to be a redeposited loess. Its even grain size has made it useful for non-ferrcus castings. and hence the many quarries in it. While the soil on the Maribyrnong Alluvium is juvenile. that on the Doutta Galla Silt is a chernozemic (prairie) soil. It has a deep well-organized calcareous profile with welldeveloped prismatic cleavage to 10 ft. This contrasts with the more variable textures. dark humus profiles. poorly differentiated nature and weak acidic reactions of the Maribyrnong Alluvium. Wood at a depth of a few feet in this formation gave a 14C age of about 1020 years B. P. Reprinted with permission from REG~ONAL GUIDE TO VICTORIAN GEOLOGY. Edited by J. McAndrew and M.A.H. Marsden, 2nd Ed., 1973
43 32 At Keilor, on the Arundel Formation, a duplex Red Brown Earth profile has a sandy A-horizon passing sharply to well-organized calcareous red clays becoming sandy in depth, and over-lying weathered boulder gravels. The three formations named can be distinguished by the nature of their sediments, by their superposition, by their internal structures, by their degree of oxidation and weathering, by their maximal height above valley thalweg, by their soils, by their type of erosion, and by their relationships with the marine formations of the Yarra Delta. REFERENCES Gill, E. D., Fluorine tests relative to the Keilor skull. Am. Jour. Phys. Anthrop., 11: Gill, E.D., Eustacy and the Yarra Delta. Proc.Roy.Soc. Vic., 74: Gill, E.D., Report for Victoria, in ANZAAS Comm. Investigation Quaternary Shorelines Changes. Austr. Jour. Sci., 25: Keble, R.A., and Macpherson, J. Hope, The contemporaniety of the Maribyrnong Terraces with those of the Upper Pleistocene of Europe. Mem. Nat. Mus. Vic., 14: POINT LONSDALE:. :.rr'fl'./ar/fy. 171 {/w slraa/;caimil/ 'r thuz- bedb< SdAAi.sWIU', ami. the,l,.'drtw; duvadp. {J/' tfu, ortr!jl7f1 lcmzfulju-. R. Vai~ee - Geot. S~v. Repo~, 1861.
44 CHAPTER DEVONIAN ROCKS OF LIL YDALE Lilydale, 24 miles east of Melbourne, is adjacent to the north end of the Late Devonian igneous complex forming the Dandenong Ranges. General geological maps of the district are included in Chapter 5 (Dandenong Ranges) and Chapter 2 (Melbourne District). The district is noted for the richly fossiliferous Lower Devonian shales, and the limestone lens at Cave Hill quarry. SILURIAN - DEVONIAN Humevale Siltstone The fossiliferous shales, the Humevale Siltstone (VandenBerg, 1971), formerly the Ruddock Siltstone, occupy a synclinorium trending NNE. To the north of Lilydale, the plunge is southerly, reversing to northerly in the south (Moore, 1965). Consisting predominantly of siltstones and shales with occasional thin sandstone bands, this unit outcrops in the Croydon lowland and much of it is covered by a veneer of alluvium. Cited thicknesses of 6000 ft. and 7500 ft. are therefore estimates. Rich assemblages occur at many localities with intervening unfossiliferous intervals, and have been partially described in a number of papers by McCoy, Chapman, Gill and others. Characteristic fossils are listed in the itinerary. The faunas, which form the basis for the old Yeringian stage, were originally regarded as Silurian in age but, initially from Ripper's (1933, 1937, 1938) studies on the stromatoporoids later confirmed by Hill (1939) on the corals and Gill (1940, 1942 etc.) on brachiopods, they have been placed in the Lower Devonian. Talent (1965), in the latest assessment of age, regards them as Siegenian, extending into the Lower Emsian in the youngest beds as at Hull Rd., Mooroolbark. Dargile Formation The underlying Dargile Formation (VandenBerg, 1971), formerly the Christmas Hills Formation, consists of some 5000 ft. of current bedded siltstones showing current ripple laminations, with occasional more massive siltstones, becoming more sandy in the upper 1000 ft. These upper beds contain rare fossils including Lissatrypa and Petrocrania, a phacopid trilobite, solitary rugose corals and Clado'pora. D. E. Thomas and P. R. Kenley (personal com.m.unication) have found 'Monograptus' (Lobograptus) scanicus near the base of the formation indicating a Lower Ludlow age, but the interval between this and the Siegenian at Ruddock's quarry cannot be date precisely. The Dargile Formation outcrops in the Christmas Hills and higher ground southwards to Croydon. The prominent easterly facing scarp of the Christmas Hills marks the Yarra Fault. The Brushy Creek scarp, near Croydon,' is attributed to differential erosion of the softer Humevale Siltstone on its eastern side. Further westwards successively older largely unfossilferous beds outcrop, culminating in the Warrandyte anticlinorium where the presence of Monograptus priodon indicates a horizon within the Upper Llandovery (D. E. Thomas, personal communication). Lilydale Lime stone The limestone quarried at Cave Hill, Lilydale, is a lenticular body overlying high horizons in the Humevaie Siltstone and probably interbedded within them. Borin~ has indicated a length of nearly one mile and a stratigraphicalthickness' of 600 ft. (Crohn, 1953). It dips eastward at an average of 60 0, flattening locally to 30 0 The limestone is a well-bedded ian Editorial Contribution
45 34, , -,-, -'-i',s.- '... 0', - - '''-,-, L RECENT E:J Alluvium TERTIARY Older Volcanics Sand,Clay UPPER DEVONIAN IT7-n Coldstniam LL.L.J Rhyolite DEVONIAN Cave Hill Sandstone LOWER DEVONIAN Lilydale Limestone Humevale Siltstone D L Outcrop obscured Limestone in bore A B.f o Feet Fig. 1. Geological outcrop map of Cave Hill, Lilydale (after Crohn, 1953).
46 35 detrital calcarenite with occasional bands containing algal pellets or oolites. Stromatoporoid and tabulate coral colonies are abundant but are not in position of growth and there is no evidence to suggest reef-building in any form. Besides the stromatoporoids described by Ripper and corals by Hill, and recently by Pedder (l965), the limestone contains gasteropods described by Etheridge f., Cresswell,and by Chapman (1916). severallamellibranchs, ostracods, and a small brachiopod assemblage of spiriferids, atrypids and rhynchonellids. Cave Hill Sandstone. In the eastern face of Cave Hill quarry the limestone is overlain unconformably by the Devonian Cave Hill Sandstone, between 100 and 200 ft. thick. The unconformity is irregular. with limestone pinnacles projecting into the sandstone. There is also an 11 0 difference in strike and the sandstone dips eastward at lower angles up to 450 as opposed to 60 0 in the underlying limestone. The Cave Hill Sandstone is strongly leached and outcrops as friable sandstone with bands of sandy conglomerate in which many of the pebbles have been sheared. Concomitant with the leaching, surface silicification has formed a layer of quartzite 10 to 20 ft.. thick which follows the contours of the hill. A small fossil assemblage including crinoid ossicles and a spiriferid occurs in the lower part and. while indicating a Devonian age, is too poorly preserved to permit more precise dating. C'oldstream Rhyolite The basal Coldstream Rhyolite of the Upper Devonian Mt. Dandenong Volcanics occurs to the east within a quarter of a mile of the Cave Hill Sandstone. Their mutual relationship has not been established but is believed to be an unconformity as the lavas in this vicinity dip eastward at only 150. There is also the possibility of local faulting. TERTIARY. Melbourne Hill is capped by a residual of olivine basalt flows which are correlated with the Palaeogene Older Volcanics. An eastward extension of this covers the limestone in the south face of Cave Hill quarry. Here the basalt overlies thin sands and clays which contain pieces of silicified and ferruginised angiosperm wood identified as Beilschrneidia. Much of this sediment was derived from the Cave Hill Sandstone which forms the eastern wall of a pre-basaltic valley. Gill (1949) considers that the basalt blocked a major south-flowing stream, the 'Wurrunjerri R. ', ancestral to the present Yarra R. The physiography of the district is discussed in Chapters 2 and 5. IN TRANSIT. ITINERARY Melbourne to Lilydale (24 miles) by Maroondah Highway. Dargile Formation and Brushy Ck. scarp at Croydon N. (18 m.). Melbourne Hill (23 m.) - Older Volcanj.cs capping - view of Cave Hill quarry with U.Devonian lavas of Dandenong Ranges to E and SEe LOCALITY 1 - Ruddockls Quarry (Loc. 20 of Gill. 1940). The type locality for the former Ruddock Siltstone, about 1000 to 1500 ft. above the base, is typical of the sediments in the lower part of the Humevale Formation and contains one of the oldest richly fossiliferous horizons. Characteristic fossils: Pleurodictyum sp., 'Chonetes' ruddockensis, Gypidula victoriae, Lissatrypa d. lenticulata, Atrypa de-::urrens, Cyrtina sub-biplicata, Hercynella sp., Ctenodonta sp. and Actinopteria sp., Notanoplia australis, Plectodonata bipartita, Leptaena sp.,
47 36 'Carinaropsis' victoriae, Straparollus~, platyceratids, hyolithids, Scutellum greenii, Gravicalymene angustior, and Cheirurus (Crotalocephalus) sp. LOCALITY 2 - Hull Road. Lilydale (Loc.l of Gill, 1940). Representative of the higher beds of the Hum.evale Siltstone,' this locality is immediately overlain by basalt and is unfortunately deeply weathered. Characteristic fossils: 'Chonetes' cresswelli. Strophonella euglyphoides, an undescribed schuchertellid, Cymostrophia sp., Maoristrophia keblei, Leptostrophia cf. affinalata, Hysterolites lilydalensis, Leptaena sp.nov., an undescribed acastid trilobite, and a number of land plants described by Dr. I. C. Cookson (1940): Zosterophyllum australianum, Hedeia cf. corymbosa, Yarravia cf. oblonga and cf. Sporogonites. LOCALITY 3 - Cave Hill Quarry. The section in this quarry - Lilydale Lime stone, Cave Hill Sandstone, pre - basaltic sands and clays, Older Volcanics - has been described above. Characteristic fossils in the Lilydale Limestone: Sterictophyllum cresswelli, Hexagonaria stevensi, Lyrielasma subcaespitosum, Heliolites daintreei, Roemeria progenitor, Favosite s spp., Alveolite s, Coenite s, Thamnopora, Tremanotus pritchardi, Bellerophon cresswelli, Phanerotrema australis, Michelia brazieri, 'Mourlonia' subaequilatera, Euomphalus ~, Scalaetrochus lindstroemi, 'Cyclonema' australis, 'Cyrtostropha ' 1ilyda1ensis, the monoplacophoran Vallatotheca nycteis, Conocardium costatum, C.cresswelli, 'Ambonychia'~, and occasional nautiloids. REFERENCES Chapman, F., On the Palaeontology of the Silurian of Victoria. Aust. Assoc. Adv. Sci., 14: Chapman, F., Some Yeringian Trilobites. Proc. Roy. Soc. Vic., 28: Chapman, F., The Yeringian Gastropod Fauna. Ibid., 29: Crohn, P. W., Lilydale Limestone Deposit. Min. Geo1. Jour., 5(1): Gill, E.D., The Silurian Rocks of Melbourne and Lilyda1e. Proc. Roy. Soc. Vic., 52: Gill, E. D., The Thickness and Age of the Type Yeringian Strata, Lilydale, Victoria. Ibid., 54: Gill, E. D., The Physiography and Palaeogeography of the River Yarra, Victoria. Mem. Nat. Mus. Vic., 16: Gill, E. D., The Devonian Rocks of Lilydale, Victoria. Vic. Nat., 82: Hill, D., The Devonian Rugose Corals of Lilydale and Loyala. Proc. Roy. Soc. Vic., 51: , Moore, B.R., The Structure and Stratigraphy of the Siluro-Devonian Sediments of the Middle Yarra Basin, Central Victoria. ~, 79: Pedder, A. E. H., A Revision of the Australian Devonian Corals previously referred to Mictophyllum. Ibid., 78(2):
48 37 Philip, G. M., Victorian Siluro-Devonian Faunas and Correlations. Congr., Pt.2: XXI Int. Geol. Ripper, E.A., The Stromatoporoids of the Lilydale Limestone Part I. Proc. Roy. Soc. Vic., 45: Ripper, E.A., The Stromatoporoids of the Lilydale Limestone Part II. Ibid., 49: Ripper, E.A., Notes on the Middle Palaeozoic Stromatoporoid Faunas of Victoria. Ibid., 50: Talent, J.A., The Stratigraphic and Diastrophic Evolution of Central and Eastern Victoria in Middle Palaeozoic Time. ill.!!.-, 79: VandenBerg, A. H. M., Explanatory notes on the Ringwood 1 :63,360 geological map. Mines Dept. Vic., Geol. Surv. Rept. 1971/1. J(fNCTJO'N 0]' TYE WONGUNGlIRRA AND WONNANGATTA RIVERS. A.W.How~ - P~og. Rep. Geot. S~v. Vic., 1877.
49 38 CHAPTER 5 THE DANDENONG RANGES IGNEOUS COMPLEX by O. P. Singleton INTRODUCTION. The nearest example to Melbourne of the Upper Devonian cauldron lavas and associated granitic intrusions so typical of central Victoria is in the Dandenong Ranges. This chapter is devoted to the sequence of acid lavas and its structural setting, the associated Lysterfield granodiorite, and the metamorphic effects in the contact zone between lavas and granodiorite. PHYSIOGRAPHY. From Mt. Dandenong (2078 ft.) remnants of three distinct erosion surfaces can be seen. The highest, preserved as monadnocks in resistant Upper Devonian igneous rocks, is represented by Mt. Macedon (3301 ft.) to the NW, Mt. Disappointment (2601 ft.) to the NNW, the ranges behind Healesville to the NE, and Mt. Donna Buang (4080 ft.) to the ENE. The intermediate surface, cut in Silurian-Devonian sediments, forms the Kinglake Plateau to the N and the Upper Yarra 'plateau, seen to the ENE th~ough th~ W'arb~rton gap. The lowe st surface, also cut in Silurian-Devonian sediments, occupies lowe'r ground in the drainage basin of the Yarra River westwards to Melbourne and eastwards in the Woori Yallock basin. This lowest surface, capped in places byolder Volcanic flows,is at least rnid- Tertiary in age, thus the higher surfaces probably date from the Mesozoic. The Dandenong Ranges are a monadnock rising above this Tertiary surface, the range itself being the youngest volcanics, the hypersthene rhyodacite. The earlier volcanics and Lysterfield Granodiorite, affected in part by Early Tertiary planation, form foothills to the range, while metamorphosed sediments in the aureole of the latter project as local ridges in the Lysterfield Hills and to the south-east of Emerald. Late Cainozoic uplift has arched the region along an E-W axis and imparted a decided westerly slope to the upper erosion surfaces. This slope together with the location of monadnocks has determined the anomalous east to west course of the Yarra River which developed as a consequent stream on the intermediate surface on the Upper Yarra plateau. Confined by the lavas of Mt. Donna Buang and by granitic monadnocks of the Powelltown Ranges on the south, it formed an outlet through the narrow gap at Warburton. From there to Yarra Glen its mature alluviated valley is cut into the Tertiary surface. Below Yarra Glen the river crosses the Brushy Creek scarp, a local base-level, and enters a gorge downstream, through Warrandyte, before' eventually reaching the depre ssed area of Port Phillip Bay. The easterlyfacing Brushy Creek scarp, crossed near Croydon has in the past been variously attributed to differential erosion or faulting. SILURIAN -DEVONIAN BEDROCK. Bedrock consists of Silurian to Lower Devonian sediments folded along meridional axes during the late Middle or early Upper Devonian (see Chapter 2)' The sediments are interbedded muddy sandstones and shales which are predominantly non-calcareous. o 5 10,! Scale of Miles Coldstrt:.am Evelyn Fault Fig. 1. Dandenong igneous complex.
50 39 UPPER DEVONIAN IGNEOUS SUITE. The Dandenong Ranges igneous suite is typical of the Upper Devonian calc-alkaline province in Central Victoria, which is dated by the occurrence of fossil fish at Taggerty and elsewhere. Very thick dominantly acid lavas accumulated in cauldron subsidences and were closely followed and intruded by granitic rocks emplaced by 'subterranean cauldron subsidence' (Hills, 1959). The Mt. Dandenong Volcanics occupy a triangular area (Fig. I}, intruded on the south by the Lyste rfield Granodiorite, which is elonga1;ed in an east-we st direction. The volcanic sequence was first elucidated by Morris (19l4) and with minor emendations his units are still recognized, and VandenBerg (197-l) gives their revised nomenclature. Hills (1941, 1959) has interpreted the structure of the lavas. A full account of the petrology and structure of the suite, upon which this account is based, has been given by Edwards (1956) while trace element studies are given by Valliullah (1964). Metamorphism of the lavas has been described by Skeats (19l0) and by Berger (196l). MouNT DANDENONG VOLCANICS. The sequence represents two phases in the development of a cauldron. Phase 1. Numerous individual flows with associated pyroclastics. Phase Coldstr~am Rhyolite ('Toscanites') - lava flows divisible into lower and upper units., 2. Mount Evelyn Rhyodacite ('Lower Dacite') - numerous flows of rhyolite, quartz rhyodacite, and quartz dacite in gradational sequence, many being fragmental, together with intercalated pyroclastic~. Major cauldron subsidence in two stages. 3. Kalorama Rhyodacite ('Middle Dacite') - thick uniform quartz-biotite rhyodacite. 4. Ferny Creek Rhyodacite ('Upper Dacite') - major single extrusion of hypersthene rhyodacite. Except for the Coldstream Rhyolite this sequence is closely similar to that in the Acheron cauldron (see Ch~pter l8). Structure of the Volcanics. There is little doubt that these volcanics accumulated in a cauldron, but in the absence of known feeders the limit of it cannot be defined. Nevertheless the present structure (Figs. 1, 2) is a reflection of cauldron collapse immediately following and perhaps during extrusion of the hypersthene dacite and prior to the emplacement of granodiorite. The eastern boundary is a combination of fault and monocline with pronounced drag in places, and the southern boundary is also faulted (Berger, 1961). The western scarp of the main range marks a monocline with steep easterly dips, so completing a triangular block within which the rhyodacite flows representing the main cauldron subsidence are confined. To the north the earlier lavas occupy a shallow southerly plunging syncline produced by gentle sagging. Coldstream Rhyolite This earliest group of flows is exposed only on the northern and western margins of the volcanic pile. The outcrops of both lower and upper units are discontinuous, a consequence of relief in the pre-volcanic topography and overlap by succeeding flows. Chemically the rhyolites differ markedly from other members of the suite, particularly in the dearth of MgO (Table 1). The lower unit is greenish to bluish-grey in colour, weathering to buff and cream, and shows gradational features between its lower and upper portions. The lower portion shows a distinctive fine platy flow structure with partial alignment of crystals in the groundmass and development of strings and lenses of minute biotite flakes. Sparse phenocrysts of andesine An40 are set in a cryptocrystalline base. Calcite is commonly present. In the upper portion the flow structure is less regular and marked by lenses of coarser biotite, calcite, and quartz. Phenocrysts and groundmass quartz are more common and locally the rocks are ve sicular. The upper units differ in their blocky jointing and lack of flow structure. They are blue-black aphanitic rocks with occasional feldspar phenocrysts and have a finer grained groundmass containing less biotite. Locally they are agglomeratic with numerous fragments of bedrock sediment and occasionally of lower rhyolites.
51 40 Mount Evelyn Rhyodacite. This division shows a similar but larger outcrop than the rhyolites. They are grey, greenish-grey, or green in colour and consist of numbers of flows with associated pyroclastics. These rocks are characterised by abundant quartz phenocrysts, scattered almandine garnets, and num.erous angular inclusions of hornfels, rhyolite and Mount Evelyn Rhyodacite. Many of them. are highly fragm.ental. The pyroclastics are m.ainlyagglom.erates, locally with fragm.ents up to 12 inches across, but thin tuffs are recorded from several localities. There is a progressive change in composition from rhyolite at the base through quartz rhyodacite to feldspathic quartz rhyodacite (Table 1). North of Montrose and at the Basin the basal ft. consists of rhyolites and fragmental rhyolites many of which show characteristic features of ignimbrites. These were more widespread,as rhyolite fragments occur in later flows of the Mount Evelyn Rhyodacite, and in agglom.erates in Kaloram.a Rhyodacite at The Patch, on the eastern flank. The rhyolites contain numerous corroded quartz phenocrysts, less orthoclase, and occasional resorbed garnet,in a glassy to cryptocrystalline base. They grade upwards into grey rhyodacites, ft. thi<,.k, which outcrop as far south as The Basin. The upper phase of the Mount Evelyn Rhyodacite (in Morris's Middle Dacite), consists of green quartz dacite outcropping along the western flank of the range. It is ft. thick in the north and thickens southwards. Clotted phenocrysts of plagioclase predominate over orthoclase and particularly quartz. Biotite both as phenocrysts and in the groundmass has been altered to chlorite with as sociated epidote and sphene N 0 Black's Quarry -'i'~':':':~'. 5 Kalorama Miles Sassafras Creek 10 S + ~ W 0 0 One Tree Hill I The Patch E WNW 3000 Mount Dandenong Silvan 0 '..'- _ -_ Miles ESE Fig. 2 (above). Geological cross sections of the Dandenong Ranges (Edwards, 1956). Fig. 3 (opposite). Geological map of the Dandenong Ranges (after Edwards, 1956). i
52
53 41 TABLE 1 - REPRESENTATIVE ANALYSES OF UPPER DEVONIAN IGNEOUS SUITE OF THE DANDENONG RANGES Z SiOZ 6S S5 6S S Z6 69.Z n ll. n Z S AI Z S S lz.s Z ' TiO Z O. ZO 0.Z5 O.ZS 0.50 Fe Z O.SO 0.57 O.SI 1. I Z I.Z 0.5Z 1. OS ZI O.Z S FeO Z.74 Z ZO Z S z.6 I Z MgO 0.Z S OS 2. SI Z.SZ CaO I. 95 I. SO NaZO IS KZO HZO I I HZO O. II 0.14 COZ I. 93 Nil. Nil Nil Nil. Nil. - Nil. Nil. Nil. Nil P Z tr tr MnO ctc Nil tr. tr IQIt.!.: 'Lowe r TOBcanite. 1I Black's Quarry, Coldstream. Analyst: P.G. W. Baylyl A. G. Hall z. 'Upper Toscanite. 1I 1 mile east of Mooroolbark. P.G.W. Baylyl A. G. Hall J Rhyolitl' J base of the Mount Evelyn rhyodacite. Quartz rhyodacite. Fcldspathic quartz rhyodacite. 1 mile east of Lilydale. North of Evelyn. 1 mile east of Boronia. A.B. Edwards, F.F. Field. G.C. Carlos, Quartz.. biotite rhyodacite. Between The Basin and Sassafras. G.C. Carlos, Hyp'orsthE'nt> rhyoda<'ite, chi.lled base. Mt. Dandenong road, N. of Kalorama. G.C. Carlos Hypersthene biotite rhyodacite. 1 mile south of Sassafras. A.B. Edwards, Calculated composition of groundmas8 of hypersthene dacite at Upwey computed from data given by Richards Biotite adamellite. East of Kalorama. F.F. Field. II. Biotite- hornblende granodiorite. I mile B.:luth of Belgrave. M. Evans. Il. Hornblende... biotite granodiorite. 4 mile s north of Pakenham. F.F. Field. 13. Ft>ldspar-hornbh.. ndr. porphyrite dyke. Lyste rfield Hills. G.C. Carlos Hornblende porphyrite dyke. Lyste rfield. G.C. Carlos
54 42 Kalorama Rhyodacite. On Mt. Dandenong road above Montrose the Mount Evelyn and Kalorama Rhyodacites are separated by a band of tuff (Fig. 4) from which Hills (1941) recorded indeterminate plant remains. Fig. 4. Position of tuffs on the Montrose Kalorama Rd. (after Hills, 1940). The Kalorama Rhyodacite is a uniform dark rock, OOOft. thick, with a chilled top and relatively free of rock fragments. It appears to be essentially a single extrusion, marking the fir st stage of final cauldron collapse. Petrologically it is a quartz - biotite rhyodacite with phenocrysts of feldspar, quartz and biotite. Similar but fragmental rocks, up to 1000 ft. thick, outcrop near The Patch, followed by up to 2000 ft. of pyroclastics which are in turn overlain by the Upper Dacite. The pyroclastics consist of agglomerates with fragments of rhyolite and toscanite interbedded with tuffs and mudstones. On the western side, north of The Basin, a thin band of tuff separates Kalorama Rhyodacite from Ferny Creek Rhyodacite. This steep-dipping band contains boulders of the underlying rhyodacite which Hills has interpreted as surface blocks buried by the tuff and subsequently rolled into it by shearing during formation of the Montrose monocline. Edwards refers to the presence in places of a zone of severely weathered rock at this. horizon,. which suggests a hiatus in volcanic activity prior to the extrusion of the Ferny Creek R;hyodacite. Ferny Creek Rhyodacite. This hypersthene rhyodacite represents the main stage of cauldron subsidence and accords in composition and position to similar extremely thick final flows in several other cauldrons. Though there is a progressive change upwards in composition it is apparently a single extrusion. It is more than 1000 ft. and could be up to 5000 ft. thick, involving the extrusion of between 7 and 35 cubic mile s of lava. The basal 200 ft. of the flow is black to blue-black in colour and is conspicuously chilled. Phenocrysts of zoned plagioclase with labradorite cores and hypersthene are set in a dense glassy base. Higher in the flow the groundrnass become s increasingly crystalline and the proportion of phenocrysts increases. With slower cooling biotite appears at the expense of hypersthene, as phenocrysts and frequently fringing hypersthene, until in the upper portion of the unit the rock is a light blue-grey hypersthene-biotite rhyodacite. Hornf~ls fragments occur mainly in the basal part. INTRUSIVE ROCKS. Lyste rfield and Silvan Granodiorite s. The Lysterfield Granodiorite is a small very high-level batholith with sharp undisturbed boundaries and was doubtless emplaced by a proce ss of major stoping involving subterranean cauldron collapse (d. Hills, 1959). Along seven miles of its northern boundary it intrudes the volcanics but while sedimentary xenoliths in varying stages of assimilation are abundant, only one of volcanic origin has been recognized. This suggests that the batholith was not roofed by volcanics but developed as a separate structure in juxtaposition to the volcanic cauldron subsidence. Small outcrops of granodiorite, scattered over about a square mile to the north-west of Silvan reservoir, may belong to a partially deroofed cupola - the Silvan Granodiorite. Quartz Porphyrite Intrusions. A quartz porphyrite intrusion, 500 yards across, occurs to the west of Silvan reservoir and metamorphoses the c-hilled base o{the Ferny Creek Rhyodacite. A similar rock, now obscured, occurs near the Silvan darn site intruding basement sediments. A third similar
55 43 body intrudes the Kalorama Rhyodacite just west of the Evelyn Fault. Lysterfield Dyke Swarm.,. A small dyke swarm intrudes the north-western corner of the Lysterfield Granodiorite and adjacent metamorphic aureole, and similar dykes occur sparsely along the northern boundary of the granodiorite. More than sixty dykes have been mapped, varying from 2-20 ft. wide and up to a mile long. F~ldspar-hornblende porphyrites predominate. A few dykes are aplitic. Petrogene sis. Edwards considered that the differentiation of rock types was the result of fractional crystallization of lime-rich plagioclase and pyroxene with gravitational settling, influenced by changes in magma composition due to assimilation of argillaceous sediments. Differentiation following similar trends was renewed after each period of extrusion, the successive magmas being of slightly different bulk composition. Oxide ratio variations show parallel serial trends for the Mount Evelyn and Ferny Creek Rhyodacites, and granodiorites, less clearly for the Kalorama Rhyodacite and dyke rocks, suggesting derivation from a common magma similar to the hornblende-bearing granodiorite. For the extrusives the order in each series corresponds to the sequence of extrusion. There is a progressive relative increase in CaO and MgO from the Mount Evelyn Rhyodacites to the granodiorites, while the Kalorama and Ferny Creek Rhyodacites are enriched in iron relative to the Mount Evelyn Rhyodacite and the granodiorites. The Coldstream Rhyolites however are relatively enriched in iron and low in CaO and particularly MgO relative to iron, indicating that they are not normal differentiates. While the CaO/AI20 3 ratios in Victorian hypersthene rhyodacites and related granodiorites are generally similar, the former tend to be richer in both oxides, suggesting gravitational sinking of Ca-plagioclase into the hypersthene rhyodacite magma. The hypersthene rhyodacite is enriched in iron presumably by. the accumulation of ferromagnesian minerals settling from higher magma levels during differentiation producing the earlier rhyodacites. Edwards considered that the presence of hypersthene rather than augite or hornblende was caused by the CaO being withdrawn in the cores of strongly zoned plagioclase phenoc,rysts during or before the crystallization of ferromagnesians, which are thus lime-free. Further he suggested that at the temperature then prevailing the magma was saturated in A1203. Subsequent reaction between hypersthene and the potassic residuum led to the formation of biotite, whereas in the slower cooling granodiorites release of CaO from early formed plagioclase allowed the formation of some hornblende. pyrogenetic almandine, indicative of Al20 3 saturation, occurs only in those lavas with quartz phenocrysts and relatively large amounts of ferromagnesians and has formed at a late stage in cooling prior to extrusion. Edwards sugge sted that assimilation of argillaceous Palaeozoic sediments, in combination with normal differentiation processes, would explain both the ~aturation in A and the abnormal compositional features of the rhyolites. Analyses of the shales show them to be non-calcareous and to contain 1-30/0 MgO and about 70/0 iron oxide. METAMORPHOSED RHYODACITES. Silurian-Devonian sediments intruded by the Lysterfield and Silvan Granodiorites have been converted to a variety of hornfelses, including biotite and cordierite-bearing types, best seen in the Lysterfield Hills where the aureole is about half a mile wide. Schistose and 'gneissic' textures in the hypersthene rhyodacite in the contact zone: 300 'to 500 yards wide,with the Lysterfield Granodiorite are the result of two distinct consecutive processes (Berger, 1961). Firstly, movement along the Selby Fault during cauldron collapse caused intense shearing in a relatively narrow zone, which with contemporaneous or later recrystallization produced strongly foliated rocks. Secondly, later emplacement of the granodiorite in juxtaposition to the down-faulted cauldron superimposed a weaker thermal metamorphism b ::>th within and outside the sheared zone. The shear zone has been traced from east of Selby westward to a point south of Upwey where it is truncated by a northward extension of the granodiorite. The degree of metamorphism decreases more or less symmetrically on either side of the central section between Selby and South Belgrave, which corresponds to the region of greatest movement on the SelbyFault. Beyond the shear zone to east and west,metamorphism was predominantly
56 44 thermal. Edwards has described essentially similar rocks where hypersthene rhyodacite has been metamorphosed by the Silvan Granodiorite and quartz porphyrite, and in which hypersthene is either rimmed or replaced by biotite. Within the shear zone the intensity of metamorphism depends on the amount of shearing the rocks have undergone and bears no relation to the proximity of granodiorite. Lenses of weakly altered unsheared rhyodacite similar to rocks outside the zone occur clol!!e to the granodiorite contact (Fig. 5), whereas high grade schists often occur in the northern half of ~1~~ ' ~~ Narre Warren Road Fig. 5. Road cutting south of Selby with granodiorite contact (after Berger, 1961). the contact zone adjacent to normal unmetamorphosed rhyodacite. In the central, most altered. sector the contact zone is an interleaved plexus of schistose rhyodacite. schist. augen schist and a few rocks with banded gneissic texture, together with lenses and pods of unsheared rhyodacite. Original rhyodacite features are still recognisable in the schistose rocks which have deveioped a good biotite foliation. Initial textures have been destroyed in the Rchists, now' composed of quartz, feldspar and biotite. Relict plagioclase phenocrysts are still present. with the foliation sweeping around them, whereas ilmenite and hypersthene have been completely replaced by biotite. and biotite phenocrysts are corroded or have recrystallized. Quartz and orthoclase have developed as porphyroblasts and in augen. OLDER VOLCANICS. Older Volcanics were extruded on the Tertiary erosion surface and occur as residuals. a'round th'; foot of the Dandenong Range s - capping Melbourne Hill, Lilydale. in a large area on the eastern side of the range near Silvan, between Emerald and Gembrook, and to the south near Pakenham and Berwick. These lavas belong to a suite of olivine,basalts whose petrology was described by Edwards (1939). This Older Volcanic suite differs from the late Cainozic Newer Volcanic suite in being less siliceous and less potassic, the development of unsaturated differentiates, the abundance of titanaugite and the rarity of iddingsite. ' ITINERARY. By Maroondah Highway to Lilydale (24 miles). Brushy Ck. scarp at Croydon N. (18m). Melbourne Hill (23 m.) - capping of Older Basalt - view of Cave Hill quarry in L. Devonian limestone lens with basalt overburden, and Dandenong Ranges with foothills to N. of Coldstream Rhyolite, overlij.in by Mount Evelyn Rhyodacite. LOCALITY 1. - Black's Quarry, Coldstream. Coldstream Rhyolite ('Lower Toscanite') showing strong vertical jointing and fine flow,banding dipping 10 0 SE. LOCALITY 2. - % mile S.E. of Lilydale. Basal rhyolites of Mount Evelyn Rhyodacite, with fragmental ignimbritic rocks.
57 45..,. LOCALITY 3. - Mt. Dandenong Rd., l~ m. above Montrose. Grey quartz rhyodaci~e member of Mount Evelyn Rhyodacite, with quartz, feldspar. and garnet phenocrysts, angular rock fragments. and interbedded agglomerates. dipping SE on Montrose Monocline. LOCALITY 4. - ~ m. beyond Loc. 3 (Fig.3). Greenish feldspathic quartz rhyodacite member of Mount Evelyn Rhyodacite. Lavas with abundant feldspar phenocrysts and chloritised ferromagnesians. overlain by tuffs with plant remains. then by dark quartz-biotite rhyodacite at base of Kalorama Rhyodacite. LOCALITY 5. - ljtm. beyond Loc.4. Top of Kalorama Rhyodacite separated by thin tuffs from chilled base of Ferny Creek Rhyodacite. dipping 70 0 _ 75 0 SE. Panorama showing erosion surfaces and Yarra River valley. LOCALITY 6. - Summit of Mt. Dandenoni (2.078 ft.) Panorama. LOCALITY 7. - Mt. Dandenong Hotel. Ferny Creek Rhyodacite - upper portion of flow containing biotite phenocrysts. Pass Sherbrook Forest to Kallista. cross John's Hill to Selby.' LOCALITY 8. - ~ m. S. of Selby. Contact zone of Lysterfield Granodiorite in central sector where metamorphism most intense - fine schist. augen schist. schistose rhyodacite, and lenses of unsheared rhyodacite (Fig. 5). Lysterfield Granodiorite. LOCALITY 9. - Glenfern Quarry. Ferntree Gully. Upper member of Mount Evelyn Rhyodacite. with steeply dipping feldspathic quartz rhyodacite flows with thin seams of tuff. View to Lysterfield Hills to S. composed of metamorphosed sediments. REFERENCES. Berger, A. R., Studies on Dacite-Granodiorite Contact Relationships in the Dandenong Ranges and Warburton Areas. Victoria. Unpublished Thesis. Univ. Melbourne. Edwards, A. B On the Occurrence of Almandine Garnets in some Devonian Igneous Rocks of Victoria. Proc.Roy.Soc.Vic.. 49(1): Edwards. A. B. > Quartz Diorite Magma in Eastern Victoria. Ibid, 50(1) : Edwards. A. B.; The Rhyolite-Dacite-Granodiorite Association of the Dandenong Ranges. Ibid. 68 : Hills. E. S Note s on the occurrence of Fossilife rous Devonian Tuffs in the Dandenong Rang~s. Ibid Hills. E. S: Cauldron Subsidences. Granitic Rocks and Crustal Fracturing in S.E. Australia. Geol. Rundschau. 47 : Morris. M On the Geology and Petrology of the District between Lilydale and Mount Dandenong. ' Proe. Roy. Soc. Vic. 26(2) : Richards. H. C On the Separation and Analysis of Minerals in the Dacite of Mount Dandenong. Victoria. Ibid. 21(2) : Skeats. E. W Gneisses and Dacites of the Dandenong District. Quart. Journ.Geol.Soc. London. 64 : Valliullah, M., A Study of Upper Devonian Volcanic Complexes in Centralrictoria.. Unpublished Thesis. Univ.Melbourne. VandenBerg. A. H. M Explanatory notes on the Ringwood 1: geological map. Mines Dept. Vic. Geoi. Surv. Rept. 1971/1
58 46 CHAPTER 6 GEOLOGY OF THE MORNINGTON PENINSULA by V.A. Gostin GENERAL. The bedrock of the Mornington Peninsula is well exposed along its axis, and consists of strongly folded Ordovician and Silurian sediments, intruded by granitic plutons of probable Upper Devonian age. The Peninsula is essentially a horst with a prominent graben to the west (the Port Phillip Sunkland) and a lesser negative area to the east (the Western Port Sunkland). The strike of the major faults is NNE-SSW, parallel to the trend of the folded Palaeozoic sediments, although several cross faults and diagonal faults are known (Keble, 1950). Several faults have shown recurrent movement and probably date back to the Palaeozoic. Many faults were active during the Tertiary and this movement has persisted to Recent times, with earthquake trerrlors originating in the Selwyn Fault zone. This fault, on the western edge of the Peninsula, is very im.portant having a throw of over 2,000 ft. during the Cainozoic. t Melbourne 12 miles Quaternary Sediments Sediments ] Older Volcanics Tertiary Mesozoic Sediments Granite ] Sediments L. Palaeozoic 4 miles PORT PHILLIP BAY N N BASS f STRAIT Schanck Fig. 1. Geological map of the Mornington Peninsula (after Keble, 1950).
59 47 SEDIMENTARY EZJ -.. '. 1:- ; 1 Tertiary ROCKS. '.. Pleistocene 1+ ' ~ 1 Upper Ordovician ~ Lower Ordovician IGNEOUS ROCKS ~ Older Volcanics Balcombe Bay Granites o I Martha Miles Dromana Bay N 1 + +t /' 1! ~I! ct! II ' / f '.,'. 1 ' 1 1 f ' 1 A A., ' /,'-, '-.'- /. ' Port Fig. 2. Geological Map of the Arthurs Seat and Red Hill area (Keble. 1950).
60 48 PALAEOZOIC. The Palaeozoic sediments are geosynclinal and have been folded into a broad anticlinorium with its main axis striking at 020 0, parallel to the length of the Peninsula. The axis passes through McIlroy's Quarry, 4 miles east of Dromana, where the oldest strata of Lancefieldian (La2) age are exposed (Locality 1). East of this axis progressively younger beds are exposed including those of Bendigonian and Castlemainian age, followed by Middle and Upper Ordovician, and some Silurian sediments on the eastern side of the Peninsula (Keble, 1950). The Ordovician sediments are estimated to be some 10,000 ft. thick, and consist of silty, generally fine grained sandstones (greywackes), graptolitic shales and slates, in a monotonous thin-bedded sequence deposited mainly under deep marine anaerobic conditions. A succe ssion of beds within the Lancefieldian consists of light coloure d unfos silife rous sandy shales and medium sandstones, and is thought to have been deposited under shallow marine conditions ('Kangerong Stage' of Keble, 1950). The greywackes are quartz rich, with some mica, chert and soda feldspar. They were probably turbidity current deposits whereas the interbedded dark shales accumulated during the quiet periods and frequently contain graptolites and pyrite (Hills and Thomas, 1953). The Ordovician strata have been silicified to a certain degree, but this has not affected the graptolites. No conglomerates, limestones or volcanic-derived sediments are known. The succeeding Silurian sediments consist of lighter coloured mudstones, shales, medium to coarse grained sandstones and a conglomerate. Fossils include brachiopods, crinoids, polyzoa and some graptolite s. Shallow marine ne ritic conditions are indicated. Igneous rocks of probable Upper Devonian age include the Dromana Granite with associated dacites at Arthur's Seat, the Mount Martha Granodiorite and the Mount Eliza Granodiorite. Around the summit of Arthur's Seat is a small patch of rhyodacite and a hornblende dacite, which have been intruded by the Dromana Granite (Baker, 1938) (Locality 3). The granite is a medium, even-grained rock with abundant greenish orthoclase. In thin section it consists of quartz, orthoclase pe rthite, oligoclase and biotite. The oligoclase is often blocky due to inte r growth with orthoclase and sometimes possesses saussuritized cores. Xenoliths are scarce. Joints and small faults are common, especially to the north-west near Selwyn Fault. The Mount Martha Granodiorite is generally grey, medium grained and consists of quartz, zoned poikilitic oligoclase, orthoclase microperthite and abundant biotite. Some hornblende is associated with biotite in dark coloured clots and has been largely altered to biotite. The Mount Eliza Granodiorite is similar but contains a greater proportion of biotite (Keble, 1950). ' ro <='1 HNI I.-i.c e-..u... 0 >4 1' to + T [,:/'::'/ I:... :1 ' <IJ ~... 0 U _UJ.u ro ~ i- + Quaternary Sediments Tertiary Sands T LOver Tert iary Volcanics Upper Devonian Granite s.>: UJ ' 0... ::l OJ.>: I-< OJ ro CIl 0 I-< 0... ~ u :<:... ~ ro...-l CIl OJ U :> ~... g <IJ....u Cfl ::l A ~1ii Silurian ~ Upper Ordovician I~ Middle Ordovician ~.u...-i ::l ro ~ ~ ' <IJ <'l ESE : ft I Sea Level Castlemainian Bendigonian Lower Ordovician Lancefieldian ('Kangerone Stage' shown in black) Fig. 3. Geological section across the Mornington Peninsula.
61 49 A raft of Palaeozoic sediments outcrops on the coast road about half a mile south of Mount Martha township. It consists of grey micaceous hornfels and quartzite. Xenoliths are also abundant in the surrounding granodiorite which is closely jointed and sheared. MESOZOIC. The Mesozoic sediments of the Peninsula occur in a very small infaulted remnant exposed on the shore platforms at.sunnyside Beach, 2 miles NE of Mornington. They consist of fluviatile arkosic sandstones and grey mudstones with a well preserved Lower Cretaceous flora. TERTIARY. The Tertiary sedimentary sequence on the Peninsula is generally flat-lying and thin (less than 300 ft. ) but thickens considerably into the flanking troughs, especially into the Port Phillip Sunkland where it is at least 1200 ft. thick beneath a Quaternary cover of 450 ft. It is best exposed along the Mt.Ma-rtha-Frankston coastline (Locality 4). Deposition may be regarded as having occurred in three phases - an early Tertiary terrestrial and volcanic phase; a marine transgression during the Miocene; and a final regressive phase leading to a return to terrestrial sedimentation in the late Tertiary. A period of intense leaching and ferruginization then occurred. As well as being intercalated in the sediments of the early Tertiary deposition phase, basalts (Older Volcanics) cover much of the southern part of the Mornington Peninsula where they reach great thicknesses and form impressive cliffs along the Cape Schank-Flinders-Phillip Island coastline (views between Localities 2 and 3). Older Volcanics. South of the Flinders Fault these lavas are at least 1300 ft. thick but elsewhere on the Peninsula they are usually less than 150 ft. thick. The lavas were extruded as many, often thin, sub-aerial flows, separated by short intervals of weathering and erosion, with occasional deposition of fluviatile sediments and lignites as at Hastings. Several closely related varieties of basalt occur. Textures range from medium to fine grained and often with much interstitial glass. Their petrology has been described by Edwards (1938) who distinguished three main types. 1. The Crinanites consist of doleritic olivine-analcite basalts which have a few phenocrysts of olivine set in a matrix of ophitic titanaugite and labradorite, with some ilmenite, needles of apatite, and interstitial analcite. Aegirine and biotite may also be present. This type is common towards the south. 2. The Moorooduc Type consists of titanaugite basalts common in the north of the area but present also at Flinders and Cape Schanck. They are medium~grained with olivine phenocrysts in a matrix of ophitic titanaugite and labradorite, and abundant interstitial glass. Chilled phase s with more glas s also occur. 3. The Flinders Type is widespread throughout the area and is characterized by the absence of titanaugite, and by ophitic structure. Olivine is present as phenocrysts in a matrix showing flow structure, and consisting of augite, labradorite, iron ore and green glass. Although Keble(1950) indicated a few possible extrusion centres on his map, the source of most of the voluminous lavas on the Mornington Peninsula is still unknown. Zeolites are commonly associated with the basalt along the Flinders-Cape Schanck coastline, and include analcite, natrolite, phillipsite, gmelinite, stilbite, thomsonite, and chabazite.
62 c Fossil Beach ~'~'i?~;0~?'i'--r-o;;'b.,u'c~~~~~;~<el Baxter Sand6to~e ---- ::;:,~< ;.c':'j-~;;'o~- ~ :--'~~~~, /~'.-:-T7/:: c:~'.:::::'- ~'=- ~-'.'.. Llh~~/~e.na} osealje,~~':' ;;< I'.(t, ' -::::-~ ''i- ~ ~ ~ '-~~ ''t ~ 'llf lcs :~',----':- calcareous'..,l,til -- Older Volca;;: '.A ~ - e ''' Vertical Exag. x :;.;;..:-/ Fossil Beach Vertical Scale /)Q' Fault ~ 1';0 f - o Miles ~ Hanyung N ~<, A ~~~~ 8 Baxt. er Sands ~ -' ;.._- tone... _ -;_-':;~. ~ /- /- / ~1 - ~-- - ~~ ~ Marina Cove Sand':'_,.,-,:~ / / I I. r, Pre-Tertiary... ~-' S. L.-. Ba~rn -s~d~a'hr,a.. tr-, -_.-. t / otl.)1-3..' :..'.?J.f:> '. r: Basement 1 I '(' ~ 1I-Pa.'C .o~o..,.: ki ';'~':-&ls',..- -;1/1 Horizontal and Vertical Scale terrestrial sed~ments... t.' 'I b's' a ft. Fault PORT PHILLIP BAY C' 0,- ' $~cq'rs e $4y Section at right angles to Manyung Fault. Fig. 4. Geological coastal sections, and locality map, of Mornington district (Gostin, 1965)..,. '...., '
63 51 Tertiary Sediments. l' In the first phase fluviatile sediments were deposited including gravels, sands and finer carbonaceous silts intercalated with which are? Oligocene basalts. The marine transgression began during the Early Miocene. At Flinders (Locality 2) a 20 ft. thick remnant of coarse to fine friable limestone (calcarenite) of Batesfordian age overlies the basalt directly, or with a thin pebble bed at the base. Between Mt. Martha and Fossil Beach (Locality 4), the Older Volcanics and overlying terrestrial sediments are succeeded by the Mt. Martha Sand Beds which represent the onset of littoral or near-shore conditions. These consist of fine grained, rounded and well sorted quartz sands, and are about 30 ft. thick, although their equivalent further north at Manyung Rocks is much thinner. A thin very coarse quartz sand unit follows the Mt. Martha Sand Beds. These coarse, paralic sediments in the Mornington District were succeeded in the Balcombian by a widespread development of deeper water calcareous and richly fossiliferous clayey silts known as the Balcombe Clay (Gostin, 1966). The type section of the Balcombian stage is at Fossil Beach, Mornington (Singleton, 1941, p.25) (Locality 4) where the Balcombe Clay is some 70 ft. thick: however, some 4 miles NE at Manyung Rocks, this unit is 170 ft. thick and ranges from Batesfordian to Bairnsdalian in age. Equivalent beds are found further north at Frankston and as isolated remnants on the central horst of the Peninsula. In the Sorrento Bore of the Nepean Peninsula, a similar facies of consolidated 'marl' and 'sandy marl' occurs and marine sedimentation in the area was probably continuous from at least the Miocene up into Pleistocene times. The fauna of the Balcombe Clay is chiefly mollusca, foraminifera and other microfossils, but includes bryozoa, sponges, corals, brachiopods, echinoids and fish. A large bibliography relating to this is listed in Singleton (1941). The maximum transgression in the Balcombian and Bairnsdalian was followed by slow withdrawal of the sea. Overlying the Balcombe Clay in the Mornington District is a thin (average 10 ft. thick) but persistent unit of a very fine, very well sorted, quartz sand, the Marina Cove Sand in which marine fossils are rare. This was deposited in a very shallow marine environment during the Upper Miocene (Gostin, 1966). The regression was completed with deposition of the fluviatile Baxter Sandstone probably in the Cheltenhamian (Upper Miocene). It is a widespread unit, usually about 40 ft. thick overlying the Marina Cove Sand, and is in part unconformable with older formations. It consists mainly of poorly sorted coarse quartz sands and clayey sands. Cross-bedding is common and wood fragments occur. The unit has been subsequently leached and heavily ferruginized. QUATERNARY In the southwest, the Nepean Peninsula extends westward towards Sorrento and Portsea. This region of low and hummocky topography consists mainly of Pleistocene dune limestone (aeolianite) developed as a bar across the Port Phillip Sunkland. It is thinly mantled by Recent dunes and swamp deposits LOCALITY 1 - McIlroy's Quarry. ITINERARY This quarry. 4 miles E of Dromana. on Dunn's Creek Road, is on the axis of the Palaeozoic anticlinorium and exposes the oldest of the Ordovician beds of the Lancefieldian stage (La 2). The beds consist almost wholly of bluish dark grey shales. the darker beds containing Clonograptus tenellus. C. rigidus. C. flexilis. C. magnificus, Tetragraptus decipiens, Bryograptus victoriae, B. clarki.
64 52 IN TRANSIT. Proceeding east and then south to Red Hill and thence to Shoreham on the shores of Western Port Bay, the road traverses Lower Tertiary Older Volcanics which is largely weathered into rich red brown soils. Thence to Flinders. LOCALITY 2 - Flinders ocean foreshore. On the south side ~f golf links a low cliff of bryozoal and foraminiferal calcarenite overlies an eroded surface of Lower Tertiary basalt. Veins of calcite penetrate the joints in the upper weathered portion of the basalt. A thin discontinuous layer of basalt gravel and quartz sand underlies the calcarenite which shows indistinct beds of various grain size. Fossils include foraminifera, polyzoa, corals, calcisponges, echinoid spines and plates, brachiopods, bivalve s and sharks' teeth. IN TRANSIT Proceeding west towards Cape Schanck the road includes the scenic views of the coastline eroded into the layered basalt flows. LOCALITY 3 - Arthur's Seat Arthur's Seat (1,030 ft.) is the highest point on Mornington Peninsula. The view from the Tower includes the low lying Nepean Peninsula to the west, the low hills, about 500 ft. high, of Mt. Martha and Mt. Eliza ( granodiorites) to the north, and the Dandenong Ranges on the horizon. The physiographic expression of Selwyn Fault is clearly marked. Several hundred yarp.s down the road towards Dromana strongly jointed granite and infaulted rhyodacite occur. LOCALITY 4 - Fossil Beach, Mornington. Fossil Beach Fault, active only during the Miocene, passes through this locality 2 miles south of Mornington. On the upthrown southern side, weathered Lower Tertiary Older Volcanics are overlain by fluviatile sands and gravels. The near-shore marine Mt. Martha Sand Beds (20 ft. thick) follow, and are overlain by 9 ft. of clayey, very coarse sand. The Balcombe Clay follows, often stained or partly cemented with yellow jarosite. On the downthrown northern side of the fault, the succession of Balcombe Clay (ca. 35 ft. exposed), Marina Cove Sand (9 ft.) and Baxter Sandstones (15+ ft.) may be seen. Here the Balcombe Clay is a homogeneous grey fossiliferous clayey silt with an average carbonate content of 20%, with layers of hard spheroidal carbonate concretions containing 80% carbonate. The old kilns were usedto produce lime from these concretions. Exposed sections are olive coloured, the upper part of which is leached and oxidised, gypsum being produced from the original calcium carbonate and disseminated pyrite. The abundant fauna is chiefly mollusca, foraminifera and other microfossils, but includes bryozoa, sponges, corals, echinoids and fish. This is the type section of the Balcombian Stage. The coast is littered with ferruginized blocks of the Baxter Sandstones. REFERENCES Baker, G., Dacites and associated rocks at Arthur's Seat, Dromana. Proc.Roy.Soc. Vic., 50: Carter, A.N. ; Tertiary foraminifera from Gippsland, Victoria and ~heir stratigraphic significance. Geo1.Surv. Vic. Mem. 23. Gostin, V.A., Tertiary stratigraphy of the Mornington District, Victoria. Proc. Roy. Soc. Vic., 79 (2). Hills, E.S., and Thomas, D.E., Turbidity currents and the graptolitic facies in Victoria. Jour.Geo1.Soc.Aust. 1 : Jenkin, J. J., The geology and hydrogeology of the Western Port Area. Underground Water Investigation, Dept. Mines Vic. Rep.5. Keble, R.A., The Mornington Peninsula. Geo1.Surv. Vic. Mern.17. Singleton, F.A., The Tertiary geology of Australia. Proc. Roy. Soc. Vic., 53(1):
65 53 CHAPTER 7 GEOLOGY OF THE GEE LONG DISTRICT by D. Spencer-Jones GENERAL GEOLOGY. In the Geelong district, pre-tertiary rocks form the higher areas comprising the Barrabool Hills, You Yangs and Brisbane Ranges. The surrounding flat to gently undulating country consists of marine and non-marine Tertiary sediments, largely covered by Quaternary basalt flows. The only exposures of Tertiary sediments of any continuity are found in the valleys of the Barwon and Moorabool Rivers. The Barrabool Hills are an uplifted block of Lower Cretaceous sediments with the upwarped remnants of Tertiary sediments and Quaternary basalts draped around the margins (Figs. 1 and 2). Low hills of Devonian? granite (Dog Rocks, etc.) protrude through the Tertiary sediments and represent a topography that was almost completely buried. The oldest known rocks are 'epidiorites' (altered basic igneous rocks - Skeats, 1908, Coulson,1930) which outcrop in small areas in the eastern part of the Dog Rocks granite. This epidiorite has been intruded by the granite (Coulson, 1930). Larger areas of epidiorite outcrop on George's Hill and Gleeson's Hill in the Barrabool Hills south of Ceres Bridge (Fig. 2), together with some granite. These two hills represent the pre-lower Cretaceous topography and massive boulders of epidiorite and granite occur in the conglomerates in the lower part of the Barrabool Hills succession. The Lower Cretaceous Barrabool Sandstone grades upwards from coarse conglomerates along the northern edge of the outcrop up to coarse feldspathic sandstones, arkose and mudstones. Abundant, although fragmentary, plant remains are found. The oldest Tertiary sediment outcropping in the district is the Oligocene (Janjukian) Waurn Ponds Limestonewhich dips gently to the south-east off the southern margin of the Barrabool Hills. Remnants of the limestone cap hills north-west of Waurn Ponds. Monoclinal flexuring in the limestone both north and south of Waurn Ponds Creek has formed an easterly plunging synclinal trough along which the creek has eroded its valley (Fig. 2). The southeasterly dip of the Tertiary sequence results in younger formations covering the Waurn Ponds Limestone to the south. In the old limestone pits on the Princes Highway, the limestone rests directly on Lower Cretaceous rocks but exploratory boring by the Victorian Portland Cement Co. Pty. Ltd., immediately to the south, has established that sands and silts of possible Eocene-Oligocene age underlie the lime stone. WERRIBEIl The Middle Miocene (Bate sfordian in part) Batesford Limestone has been proved by drilling to be confined to the eastern and south-eastern sides of the Dog Rocks granite mass, which is thought to have been an island at this time (Bowler, 1963). Shallow water rock-dwelling forms may have provided the calcarenite debris which was deposited in slightly deeper water (Foster, 1970). The limestone grades vertically and laterally into earthy limestone, marls, silty clays and silts of Middle to Upper Miocene age (Batesfordian to Bairnsdalian) forming the Fyansford Clay. In natural exposure before quarrying, the Batesford Limestone outcropped in the Moorabool River valley south of the Ballarat Road and dipped Fig. 1. Major structures of the Geelong district. Volcanic erudtive centres ~
66 54 s 0 1 2?... Horiz. scale - miles Vert. scale - feet 1'-- Marl and limestone Limestone Marl and limestone Fig. 3. Geological sections across Geelong district beneath the valley floor on a gentle south-easterly dip. The Fyansford Clay outcrops along the east side of the Moorabool valley northwards from Orphanage Hill at Fyansford. Carter (196l) regards the section exposed here as Upper Miocene (Bairnsdalian) in age. Outcrops of silty clay, marls and sandy limestones in the cliff sections at Western Beach and North Shore, Corio Bay, have been considered as facies variants of the Fyansford Clay (Bowler, 1963). The formation dips gently to the north and is Upper Miocene (Bairnsdalian) in age. The Moorabool Viaduct Sands (Bowler, 1963) of Pliocene age is a thin sequence of sands, sandy clays, calcareous sandstones and overlies the Fyansford Clay with a slight disconformity. At the disconformity there is a discontinuous layer of phosphatic nodules derived from the underlying sediments. The Moorabool Viaduct Sands originally covered the area of Tertiary sediments as a thin veneer of marine and non-marine origin, deposited during regression of the sea. At the type locality. the Railway Viaduct crossing the Moorabool River. marine sediments of Lower Pliocene (Kalimnan) and Upper Pliocene to Lower Pleistocene? (Werrikooian) age have been established from fossil collections. Elsewhere fossils can be found but their poor preservation prevents accurate age determination. The Quaternary basalt flows (Newer Volcanics) covered most of the Tertiary sediments leaving only the higher topography exposed. During the Pleistocene. lakes were formed by the disruption of drainage systems by the vulcanicity and freshwater limestones, sands and clays formed in some of these lakes e. g. limestone at Lara and Limeburners Point. Marsupial bones and freshwater molluscs were found in these limestones (Pritchard, 1895). GEOMORPHIC EVOLUTION. The interplay of tectonic movements and vulcanicity. particularly during late Tertiary and Quaternary times. has resulted in a geomorphic evolution of considerable complexity much of which is yet to be elucidated. During the early marine transgression even the area of the Barrabool Hills must have been inundated. This is indicated by the presence of residuals of Waurn Ponds Limestone capping some of highest parts. The initial movements leading to the emergence of the Barrabool Block or Horst commenced between Oligocene (Janjukian) and Upper Miocene (Balcom bian) (Coulson. 1960). Marine deposition continued in the othe r parts of the area with limestone being deposit~d in marginal environments e.g. Batesford Limestone. and marls. Fig. 2 (opposite). Geological map of the Geelong district.
67 Recent Alluvium ~..: H 8 c:r:: ril 8 Pleistocene L.Pliocene Miocene Oligocene L.Cretaceous Devonian Cambrian Alluvium, coastal de;'losi ts Freshwater Limestone Etc. ~} a Newer Volcanic - basalt 0 Moorabool Viaduct Sands ~ Fyansford Clay Batesford Limestone ES3 bs E±l Waurn Ponds Limestone Barrabool Sandstone Granite ~ Epidiorite v v V V v v v v v v v v v v v v v v v v I V V V V V v, I ', V V V, y ' v V v ', , _,;9.-, ' v,. v y v, V v It' v ': j, (=:~:; I -1 v V V V V ' v V V V V V V v v v, v v y v v v v v v v v v v v v v v v v v v v v v v ' v v 'ti'.,~~..., v v v Z:_::: v v v v v v V v v ' v v v V I,. v, v v y v, /. v v.'. v ' ' v Shore CORIO BAY GEOLOGICAL MAP OF THE G 1<~F.rJONn. DISTRICT o 2 Scale in miles ' v
68 55 sandy clays, silts, sandy limestones in deeper waters during Middle to Upper Miocene. Sedimentation was continuous in the Geelong District but further inland several transgressive and regressive phases occurred (Bowler, 1963). In the Lower Pliocene, broad uplift initiated the regressive phase associated with erosion and deposition of the nodule bed and thin clastic sediments. Following the withdrawal of the seas in late Pliocene or early Pleistocene extensive flows of Newer Volcanics covered most of the area. Movements on the Rowsley Fault, Lovely Banks Monocline and around the margins of the Barrabool Hills (Fig. 1) displaced the basalt flows of this earlier phase and movements along the Lovely Banks Monocline and the Newtown Fault influenced the courses of the Barwon and Moorabool Rivers. These streams eventually eroded wide valleys in the vicinity of and upstream from their junction, but due to repetitive movements on the Newtown Fault, the Barwon eroded a narrow valley through the eastern end of the Barrabool Hills. Later basalt flows partially filled these valleys, the flows banking up in the vicinity of Fyansford because of the narrowing of the valley. Continued movements on the Newtown Fault forced the Barwon River to cut a gorge downstream from Queen's Park through this valley-filling flow. These younger valley-filling flows have been dated in the Moorabool River and at Pollocksford at about 2. 1 m. y. (Aziz-Ur Rahman and McDougall, 1972) indicating that tectonic movements possibly persisted into the Pleistocene. ITINERARY LOCALITY 1 - Lara Limestone (Pleistocene). A pit in freshwater limestone. The limestones, sands, fine gravels and clay outcrop in the Lara District and in the valley of Hovell Creek. The se sediments overlie the basalt at Lara, but in Limeburner's Bay similar sediments occur between basalt flows. Coarse angular quartz and mica is included in the limestone suggesting that part of the source for detritus was the granitic rocks of the You Yangs. A freshwater mussel cf. Unio australis, Lamarck has been recorded from Lara and a palate and molar teeth of Diprotodon longiceps McCoy from Limeburner's Point on the south side of Corio Bay (Pritchard, 1895). An analysis of the limestone is - CaC03 MgC03 FeC03 Silica and clay 88.38% 0.76% 0.51% 7.020/0 LOCALITY 2 - Batesford - Landslip on east side of Moorabool River Valley. Pleistocene (Newer Volcanic) Pliocene (Moorabool Viaduct Sands) Miocene Tertiary Section (After Singleton, 1941) Fyansford Clay Disconformity Bate sford Lime stone Basalt White sands Brown ferruginous sands Nodule bed 6 ft. 16 ft. 15 ft. Yellow and grey clays, marls, 30 ft. more calcareous towards base. Earthy limestones 30 ft. White bryozoal calcarenite Lepidocyclinal calcarenite 30 ft. 45 ft. The Moorabool Viaduct Sands underlie the basalt and overlie disconformably the richly fossiliferous Fyansford Clay. The upper part of the Moorabool Viaduct Sands is white to grey and grades down to yellowish brown limonitic, bedded sands with some hard calcareous beds. These lower beds are fossiliferous but the poor state of preservation has prevented any accurate identification. The nodule bed is discontinuous at the base of the Moorabool Viaduct Sands. The richly fossiliferous clays, marls, and earthy
69 56 limestones are included in the Fyansford Clay and vary from the Balcombian to Bairnsdalian in age. The bryozoal and Lepidocyclina limestones are included in the Batesford Limestone as defined by Bowler (1963) for the Batesford Quarry section. LOCALITY 3 - Dog Rocks. Granite is coarse grained, porphyritic and supplied terrigenous debris in the lower parts of the Batesford Limestone. Prominent joints, aplites etc. Panoramic view to north, west and south of You Yangs, Anakies, Rowsley Fault Scarp, Barrabool Hills, Barwon River Valley, Mt. Moriac and Mt. Pollock basalt eruption centres, and the George's Hill and Gleeson's Hill inliers of epidiorite. LOCALITY 4 - Batesford Quarry of Australian Portland Cement Ltd. As defined by Bowler (1963) the Batesford Limestone includes all the calcareous sediments overlying the granite and underlying the Fyansford Clay in the quarry area. The present face exposes 110 ft. of the limestone and at least another 100 ft. underlies the quarry floor. The Batesfordian Stage was defined by F.A. Singleton (1941) as 'the interval of time represented by the deposition of the Lepidocyclina - bearing limestones of the Batesford quarries', but as pointed out by Bowler (1963) since only the upper part of the limestone exposed in the quarry contains Lepidocyclina then the remainder of the limestone sequence is excluded from the definition. The lower parts of the limestone could be Lower Miocene (Longfordian) in age or older. Bowler established that the detrital content of quartz, felspar and mica showed lateral and vertical decrease away from the granite. Carbonate content inc rease s above the quarry floor in the working face. The mate rial below the pre sent quarry floor is not of high enough grade for cement manufacture. A typical analysis of limestone supplied by Australian Portland Cement Co. Ltd. is - SiOZ 16.68% S % AlZ0 3 Z.83 KZO 0.75 Fe Z Na~O 0.70 CaO Ignition 10 s s MgO 0.84 Exploratory drilling by the company has established that the limestone interdigitates and passes laterally into marly sediments to the south and south-east. Overlying the limestone there are well-bedded earthy limestones, marls and clays (Balcombian) which grade up into predominant marls and clays (Bairnsdalian). Basalts of the low level flow of the Moorabool River valley rest directly on the Miocene sediments, the Moorabool Viaduct Sands having been eroded away. The surface of the Batesford Limestone is undulating and slumping of overlying sediments into caves in the limestone results in fold structures in the limestones, marls etc. higher in the sequence. LOCALITY 5 - Newtown Lookout. View of the Barwon R. valley and junction with the Moorabool R. valley. Barwon R. valley narrows whe re the river has cut a gorge through the uplifted valley flow. The Newtown Fault to the south brings the Tertiary section of Orphanage Hill in contact with the Barrabool Sandstones (Lower Cretaceous). Quarry in low level basalt at Fyansford where relatively thick lava (160 ft.) has been proved by boring. The difference in level between this basalt and the flow on which the Newtown Lookout is built is obvious. To the south the remnants of the valley flow can be seen along the edge of the Barrabool Hills. To the east the country falls away to Corio Bay, the change in elevation being due to the southern limits of the Lovely Banks Monocline. IN TRANSIT - Locality 5 to Locality 6. From Ceres Bridge on the Barwon River, Gleeson's Hill (on the left) and George's Hill (far right) can be seen with visible outcrops of epidiorite. The hill between these is capped by Tertiary limestone probably of the same age as the Waurn Ponds Limestone.,
70 57 LOCALITY 6 - Quarry near Ceres. Quarry in typical Lower Cretaceous arkosic sandstone of Barrabool Hills. Sandstone is cross bedded; some calcareous concretions are visible. Abundant coalified plant remains occur on bedding planes IN TRANSIT - Locality 6 to Locality 7. Approximately Yz mile north of Waurn Ponds, a small limestone pit on brow of hill to east shows dipping lim.estone beds. Here the Waurn Ponds Lim.estone is resting on Lower Cretaceous rocks and is dipping to the north on a monoclinal flexure. LOCALITY 7 - Waurn Ponds Limestone pits. The Waurn Ponds Lime stone as mapped on the 1 :63,360 geological map of Geelong include s all the fossiliferous limestone, marl and clay which outcrop in the valley of Waurn Ponds Creek. Here the limestone rests unconformably on the Lower Cretaceous Barrabool Sandstone s, with rounded boulders of Eocene Older Volcanic basalt at the base. The limestone is richly fossiliferous and extensive collections have been m.ade from. it. The limestone was given a Janjukian (Oligocene) age by Hall and Pritchard (1902), which was subsequently confirmed by Carter (1961). Three east-north-easterly trending monoclines displace the 30 ft. limestone bed (Fig. 1) but south of these old quarries a gentle south-easterly dip prevails in the Tertiary sediments. Limestones of identical lithology to the limestone at Waurn Ponds outcrop along the south side of the Barwon River near Belmont. On present evidence these are considered as being Janjukian in age. LOCALITY 8 - Victorian Portland Cement Co. Pty. Ltd. Quarry. The south-easterly dip is apparent in the faces of the quarry. The following generalised sequence has been supplied by the operating Company: Unit Thickness Recent to Pleistocene Pleistocene Pliocene Lower Miocene (Longfordian) Oligocene (Janjukian) Eocene? Clay Basalt Typical analysis of limestone and marl is - LOCALITY 9 - Western Beach. Corio Bay. Silty clay with limonitic concretions towards base Sandy marl with subordinate low grade limestones Marl with low grade limestones Bryozoallimestone Silts, sandstones, mudstones, carbonaceous silts. Bryozoal Lim.estone 0-10 ft ft. 60 ft. (max) ft. Marl SiOZ 5.0% 37.0% A Fez CaO MgO ft. 33 ft. The cliff section contains silty clay, marls and nodular and concretionary limestones considered by Bowler (1963) as variants of the Fyansford Clay. These sediments are overlain at the disconform.ity by the nodule bed, and cross-bedded reddish brown sands forming the Moorabool Viaduct sands.
71 58 The Fyansford Clay sediments outcrop almost continuously along Western Beach to North Shore and dip gently northwards. The dis conformity truncates progressively younger beds as the outcrop is traced northwards. Carter (1961) recorded three thin limestone beds, the middle one being sparsely fossiliferous containing Ornrnatocarcinus corioensis and Hinnites corioensis. The silty clay and marl have been given a Upper Miocene (Bairnsdalian) age by Carter., REFERENCES Aziz-Ur-Rahman, and McDougall. I., Potassium-Argon ages on the Newer Volcanics of Victoria. Proc. 'Roy. Soc. Vic. 71, Baker, G., The petrology of the You Yangs granite. A study in contamination.proc.roy. Soc. Vic. 58, Bowler, J.M., Tertiary stratigraphy and sedimentation in the Geelong - Maude area, Victoria. Proc.Roy.Soc.Vic. 76, Carter, A. N., Some notes on the Cainozoic stratigraphy of the Geelong area. Unpublished Report, Mines Department (Victoria) 1963/4. Cookson, I. C., and Dettman, M.E., Some trilete spores from the Upper Mesozoic deposits in Eastern Australian region. Proc. Roy. Soc. Vic. 70, Coulson, A., On the relationship of epidiorite and the granite at Barrabool Hills and Dog Rocks near Geelong, Victoria. Proc. Roy. Soc. Vic. 42, Coulson, A., The basalts of the Geelong District. Proc.Roy.Soc.Vic. 50, Coulson, A., Some structural features of the Barrabool Hills. Proc.Roy.Soc. Vic. 72, Edwards, A.B., and Baker, G., Jurassic arkose in southern Victoria. Proc.Roy,Soc. Vic. 55, Foster, R. J., Origin of Batesford Limestone (Miocene), Victoria. Proc. Roy. Soc. Vic. 83, Hall, T. S., and Pritchard, G. B., A suggested nomenclature for the marine Tertiary deposits of southern Australia. Proc.Roy.Soc. Vic. 19, Hills, E.S., Physiography of Victoria. Whitcombe and Tombs. Melb. Me dwell, L.M., A review and revision of the Flora of the Victorian Lower Jurassic. Proc. Roy. Soc. Vic. 65, Pritchard, G. B., Geelong Naturalist 4, Singleton, F.A Tertiary geology of Australia. Proc.Roy.Soc.Vic. 53, Skeats, E. W., Notes on the geology of the You Yangs, Victoria. Rep.Aus.Ass.Adv.Sc. 11 (Adelaide 1907), Spencer-Jones, D., Explanatory notes on the Geelong 1: 63,360 Geological Map. Geol. Surv. Vic. Rept. 1970/1.
72 CHAPTER 8 59 GEOLOGY OF THE BACCHUS MARSH DISTRICT by O. P. Singleton INTRODUCTION. The Bacchus Marsh district acquired world-wide fame during the last century as one of the earliest known occurrences of ancient glacial deposits. first recognised by Selwyn in 1861 and shown to be Upper Palaeozoic in age by McCoy. This Permian sequence demonstrates admirably many of the characteristic features of glaciation and glacial sedimentation. The geology is dominated by faults dividing the district into a number of blocks. each with a somewhat different geological history (Fig. I). The youthful N-S Rowsley Fault (F5). with its well-preserved scarp up to 900 ft. high. separates the depressed Werribee Plains (E) from the elevated and dissected plateau to the west. This in turn is divided by the E-W trending Greendale (F2) and Spring Creek Faults (Fl) into three blocks forming from north to south the Lerderderg Ranges (A), Ballan Graben (B), and Brisbane Ranges (C). To the east of the Rowsley Fault the E-W Gisborne Fault (F3) and smaller Coimadai Fault (F4) separate the Werribee Plains from the Gisborne Highlands (D) on the north. The faults die out to the east. Faulting on the E-W trend antedates movement on the Rowsley Fault and dissected scarps remain -only on the Greendale and Gisborne Faults. The Lerderderg and Brisbane Ranges consist of Ordovician bedrock. the former with small outliers of Permian. the latter covered with a veneer of Tertiary to the south. The BalIan Graben. subsiding intermittently from the Permian onwards. contains thick sequences of Permo-Triassic sediments. Tertiary Older Volcanics and overlying sediments. and is partially capped by flows of Newer Basalt. Bedrock is exposed only in a small area in the Werribee Gorge where an adamellite stock intrude s the Ordovician. The Gisborne Highlands also consist of Ordovician. partly covered by lows from a number of Newer Volcanic vents. The Werribee Plains are a sheet of Newer Volcanic basalt lows up to 250 ft. thick. underlain by thick Tertiary sediments, including a 100 ft. brown coal seam. with marine Miocene sediments known to the SE of Bacchus Marsh. The Tertiary sequences wedge out northwards and the underlying Permian and Ordovician are exposed. Fig. 1. Block diagram of the Bacchus Marsh district (after Fenner) - for symbols see text above.
73 60 ORDOVICIAN. Bedrock in the area is typical of the geosynclinal Ordovician sediments in central Victoria, being a very thick monotonous alternation of low-rank greywacke and slate. The sandstones are usually fine grained, with occasional coarser units, and frequently show graded bedding and other structures indicative of emplacement by turbidity currents. The slates are graptolitic with assemblages representative of the faunal sequence for which the Victorian Ordovician is renowned. The rocks are tightly folded on meridional axes, superimposed on larger scale dome and trough structures. Near Bacchus Marsh the beds belong mainly to the upper part of the Lower Ordovician, with older divisions exposed in domes near Blackwood and Coimadai. To the east the Djerriwarrh Fault separates Lower from Upper Ordovician. ADAMELLITE. A small stock of adamellite, presumed to be Upper Devonian in age, intrudes the folded Ordovician in the upper part of the Werribee Gorge. Associated acid dykes both here and in the Lerderderg Ranges have N-S trends parallel to the strike of the Ordovician rocks. PERMIAN AND TRIASSIC. The Permian sequence and overlying Triassic have been studied for the past hundred years yet the first marine fossils were only discovered in 1965 at Bald Hill (Thomas, 1969). A small conglomerate lens near the base of the section at Coimadai has yielded a small Early Permian marine fauna (Garratt, 1969). Many contributions have been made including studies by Bowen (1959) and recently by Crowell and Frakes (1970). Permian sediments are preserved on the down-thrown Ballan and Werribee Plains blocks, with thin outliers north of the Greendale Fault in the Lerderderg Ranges. Due to later faulting and cover by yo.unger rocks, individual sections are incomplete and correlation is difficult. The thickest and most continuous section is the composite one on Korkuperrimul Creek and Bald Hill (Jacobson and Scott, 1937; Bowen, 1959). The lower glacial sequence with its base truncated by the Greendale Fault is some 3,000 ft. thick, including 39 individual tillites interbedded with water-laid conglomerates, sandstones, and occasional siltstones. The glacial phase is followed conformably by 250 ft. of well sorted bedded sandstones which at the top contain Gangamopteris and an Equisetalean. These plants enabled McCoy to demonstrate the Upper Palaeozoic age of the glaciation. These non-marine beds are truncated by an unconformity succeeded by a conglomerate and pebbly sandstone, some ft. in all, which have yielded Notoconularia inornata (Thomas, 1969), thus indicating a brief marine intercalation. The conglomerate, described previously as a 'winnowed tillite:' is better considered as a conglomerate basal to this marine intercalation. The marine horizon is followed conformably by 320 ft. of unfossiliferous bedded sandstones and mudstones with occasional pebble bands, at the top of which a one foot mudstone band yields fragmentary leaf remains. These were described by Chapman (1927) and assigned to the Triassic. Although most of the fossils are unidentifiable J. Douglas (personal communication) is convinced of their Mesozoic age. A further few feet of conglomerate and sandstone completes the section. The basal Permian unconformity shows some hundreds of feet of relief notably in the sub-glacial valley at 'The Island' in the Werribee gorge. The unconformity surface is glaciated and pavements are exposed at a number of localities. These are polished and striated, the prevailing direction being from SW to NE. The tillites vary considerably in lithology from completely unsorted and unstratified boulder clays to units in which the matrix shows some degree of sorting and others showing some evidence of stratification. With increasing influence of melt-waters, the lithologies grade into obviously water-laid resorted sediments. Crowell and Frakes (1970) have suggested that many of the diamictites previously called tillites are the result of the mobilisation of till by mud flow activity. Erratics in the basal tillites corne predominantly from the local Ordovician sandstones but higher in the sequence the proportion of exotic erratics increases. These include a variety of granitic types, rhyolite, quartzite, conglomerate, schist and gneiss, in most cases of unknown source. A proportion of the erratics are facetted and striated. The ratio of erratics to matrix in the tillites varies considerably. The interbedded water-laid periglacial sediments are predominantly conglomerates and sandstones with lesser amounts of siltstone and mudstone. They tend to be poorly sorted, with,.. Fig. 2 (opposite). Geological map of the Bacchus Marsh district.
74 v v v v VICTORIAN GEOLOGY' V V I I I I V.- -, V ;v / / V V, V V * V v -,...~----., V V V V V :V V, V ' I I I I I,V V V V V v V ' V V V ',V V,V v v V V V V V ---v---- v v V V V V V V ----V ----~~~~ V - V V V V v V V 600 v v v MT. WALLACE v v * V Y.IT. HYDEWELL v V V V v v Alluvium Gravel, sand etc. Older Volcanics ~ t N Adamellite Tillite, conglomerate, sandstone, mudstone SCALE IN MILES Fault Railway Road Sandstone, slate, shale ORDOVICIAN DEVONIAN ~ PERMIAN Sandstone, mudstone TRIASSIC gravel, lignite Sand, Clay, Vent ~ ~ * TERTIARY Newer Vo lcanics ~ PLEISTOC ENE CJ RECENT GEOLOGICAL MAP OF TH E BACCHUS MARS H REG I ON
75 61 cross-bedding and scouring prominent. Occasional large boulders appear to have been dumped into the sediment from floating ice. S::>me of the fine-grained beds are thought to be lacustrine but, although known elsewhere in Victoria, no undoubted varves have been found at Bacchus Marsh. In contrast the post-glacial sediments are more evenly bedded and better sorted, and pebble beds are infrequent. Besides the fossils referred to above, Permian spores have been isolated from a number of samples within the glacial suite. The relationship between Permian and Triassic appears to be conformable, however further detailed examination of this part of the sequence is desirable. TERTIARY. Pentland Hills Volcanics. Basic lava flows correlated with the Paleogene Older Volcanics are confined to the Ballan Graben. On the Korkuperrimul Creek a sequence of flows at least 550 ft. thick includes a variety of olivine-titanaugite basalts, olivine nephelinite grading into nepheline limburgite, limburgite and limburgite basalt (Jacobson and Scott, 1937; Edwards, 1940). An associated E-W trending dyke swarm is distributed through the Lerderderg Ranges and BalIan Graben, intruding Ordovician and Permian sediments and occasionally the basalts, but never the overlying Tertiary sediments. Rock types include monchiquite, basalt, camptonite and occasionally olivine nephelinite. Te rtiary Sediments. Non-marine Tertiary sediments, up to ilbout 800 ft. in thickness in the Parwan valley, are widespread in the BalIan Graben and east of the Rowsley Fault. Elucidation of their stratigraphy is complicated by the general similarity and varied distribution of lithologies and by the absence of palaeontological control. However, Thomas and Baragwanath (1950) have recognised a number of formations in the Parwan valley and at Bacchus Marsh. At Bacchus Marsh a sequence of clays, sands and gravels is overlain by the Maddingley brown coal seam, up to 103 ft. thick, which is exploited in open cuts on the lower Parwan Creek. This seam wedges out rapidly northwards beneath the Bacchus Marsh basin but maintains its thickness south-eastwards. Six miles SSE of Bacchus Marsh it is overlain by marine late Lower to Middle Miocene clays and marls which contain an 11 ft. intercalation of brown coal 28 ft. above their base (Parr, 1942). Thus the Maddingley seam, continuing into the Lower Miocene, is the youngest of the thick brown coal seams in Victoria. These marine beds are absent at Bacchus Marsh where the coal is followed conformably by fluviatile sands. In the Parwan valley some hundreds of feet of clays with intercalated gravels and sands contain at depth at least one thick coal seam which is probably a western extension of the Maddingley seam. These are overlain by sands and conglomerates. Elsewhere non-marine sediments overlie the Older Volcanics and, where ferruginised, yield leaf impressions. NEWER VOLCANICS. Olivine basalt flows emanating from numerous volcanoes cover the Werribee Plains and occur as valley flows in the higher country. The contrast between lava field and valley flow is illustrated very well by the basalts issuing from Mt. Cotterill near Melton and from Mt. Bullengarook. Mt. Cotterill is surrounded by a gently sloping shield some five miles across, formed by numerous radial flows. Mt. Bullengarook produced flows to north and south, the latter filling a gently sloping valley for some 12 miles. This Bullengarook flow now caps the interfluve between the twin lateral streams of Goodman I s Creek and Pyrete Creek. The volcanic hills include both lava and scoria cones but do not in general have their craters preserved. The Newer Volcanics range in age from Pliocene to Recent and from their state of preservation and physiographic setting those in the Bacchus Marsh district are probably Pliocene. QUATERNARY SEDIMENTS. Following p::>st-newe r Volcanic movement on the Rowsley Fault an apron of conglomerate and sand accumulated along the fo :>t of the scarp and spread out over the basalts. Similar gravels overlie the basalts on either side of the Werribee River valley downstream from the Bacchus Marsh basin and antedate the entrenchment of that stream.
76 62 Subsequent to entrenchment of the Werribee River into the basalt plain and development,by erosion of the Bacchus Marsh basin, the latter has been covered by a veneer of fertile alluvial deposits from the Werribee and Lerderderg Rivers. COIMADAI LIMESTONE. Several small outcrops of fresh water dolomitic limestone and clastic sediments occur in the valley of Pyrete qreek at Coimadai. Thin bands of weathered basaltic material, usually recorded a,s volcanic ash, are intercalated, nevertheless the age relationship to the Newer Volcanics is unknown. This limestone contains a small marsupial fauna which is currently being redescribed by W.D. Turnbull and E.L. Lundelius. FAULT MOVEMENTS. The pattern of fault movements indicates that the set of E-W faults operated for a considerable period of time but became inactive before the main movement on the Rowsley Fault. The presence of such a thick Permian sequence in the BalIan Graben strongly sugge sts faulting contemporaneous with deposition. The BalIan Graben has a general southerly tilt with the youngest Tertiary sediments best developed near its southern margin. As a generalisation repeated movement on the boundary faults between the Triassic and late Tertiary has imposed higher dips on successively older rocks. However the BalIan Graben is not a single entity, being cut by a number of smaller faults mostly parallel to the boundary faults so that dip directions vary locally. Both the Greendale and Spring Creek Faults are crossed by Newer Volcanic flows without displacement but slight warping of the Bullengarook flow has occurred on the Gisborne Fault. With this exception, the E-W faults became inactive before extrusion of the Newer Volcanics. In contrast movement on the Rowsley Fault is largely if not entirely post-newer Volcanic in age. PHYSIOGRAPHY. The physiography has been described in detail by Fenner (1918). Its development began with the early Tertiary erosion surface, represented by concordant summits in the Ordovician sediments of the Brisbane, Lerderderg and Gisborne Ranges. Until the Pliocene this surface remained close to base level but was depressed under the Werribee Plains and in the subsiding BalIan Graben. During the Pliocene the Western Highlands of Victoria were arched about an E-W axis and this erosion surface elevated to 2,500 ft. in a domal structure to the north of the area. Contemporaneous movement on the Greendale and Gisborne Faults prod'.lced southerly facing scarps, still preserved in modified form. Upon this warped surface the pre-newer Volcanic drainage system developed. Extrusion of the Newer Volcanic lavas filled many of the shallow valleys. spread over the Werribee Plains and part of the BalIan Graben, and caused alterations to the drainage. There followed early in the Pleistocene the main movement on the Rowsley Fault which. together with movement on a number of other structures. produced the drowning of Port Phillip Bay. The Rowsley Fault caused strong rejuvenation of the Lerderderg and Werribee Rivers and Parwan Creek. The Lerderderg River, draining an uplifted block of Ordovician. has cut a spectacular gorge 1,000 ft. deep and dissection by its tributaries is deep and intricate. The Werribee gorge is also spectacular in the short stretch in Ordovician and adamellite, where it is 600 ft. deep. Downstream the valley widens out in softer Permian and Tertiary sediments. The Parwan Creek has a wide val,ley containing residual mesas, eroded from soft Tertiary sediments capped by basalt flows. 'rhe basalt protects the sediments and erosion is largely by land slipping in the latter. Dissection of the Gisborne highlands by headward erosion has reached the stage where the overlying lavas from Mt. Gisborne are beginning to be dissected. The origin of the Bacchus Marsh basin was explained by Fenner. It occupies an area which was not covered by the Newer Volcanics and is flanked on the east by the Bullengarook flow and on the south by flows from Bald and Spring Hills. Below its junction with the Lerderderg River the Werribee River flowed eastward along the junction between these before being diverted southwards at Melton Reservoir by the lava shield produced by Mt. Cotterill. As the Werribee River cut a gorge through these basalts both it and the Lerderderg River removed the Rowsley Fault apron a~d underlying soft Tertiaries. With base-level controlled by the gorge downstream, widening of the basin has been accomplished by undercutting of the flanking lava flows, and at present the Bacchus Marsh basin lies 200 ft. below the level of the plain.
77 63 ITINERARY IN TRANSIT - Melbourne to Coimadai. Leave Melbourne by Calder Highway. Keilor (10 miles) - Maribyrnong R. valley cut in L. Silurian sediments, Tertiary gravels, and Newer Volcanic basalts. Digger's Rest (20 m.) - Newer Volcanic volcanic hills in the Gisborne Highlands (see Chapter 11). Pass Mt. Kororoit (23 m.) on left-volcanic cone crossed by N-S dyke. Toolern Vale (28m.) - dissected scarp of Gisborne Fault on right. Coimadai (34m.). LOCALITY 1 - Alkemade's Quarry Coimadai. Fresh-water Coimadai limestone containing rare marsupial bones. LOCALITY 2 - Pyrete Ck. section, Coimadai. Basal Permian sediments are exposed intermittently in the banks of Pyrete Ck. The 'Pyrete Twins ' a 'roche moutonle' of indurated Ordovician sandstone plastered with tillite have a well-preserved pavement showing fluting, polishing, striations from SW to NE and plucking on the lee side. Upstream the basal tillite is overlain by water-laid poorly sorted sandstones and mudstones with pebble bands and occasional dumped boulders. One layer is extensively burrowed. LOCALITY 3 - Bullengarook basalt flow 137m.). Panorama.. To N Mt. Bullengarook (2,207 ft.) and lava flows warped on Gisborne Fault, with twin lateral streams Goodman's Ck. (west) and Pyrete Ck. (east). To NE dissected Gisborne highlands capped by lavas from Mt. Gisborne (2,109 ft.). To E dissected scarp of Gisborne Fault. To SE Werribee Plains. To S granitic You Yangs (1,154 ft.) on skyline, Bacchus Marsh basin with Rowsley Fault scarp on W. To SW and W, in order, Brisbane Ranges, BalIan Graben, and Lerderderg Ranges with mouth of Lerderderg gorge and Mt. Blackwood (2,415 ft.), shelf of dissected Ordovician at foot of Rowsley scarp. Travel S along Bullengarook flow. Descend into Bacchus Marsh Basin (44m.) Tertiary sediments underlying basalt. LOCALITY 4 - Lerderderg R. section, Darley (46m.). About 500 ft. of Permian dipping S is exposed along the Lerderderg R. downstream from the mouth of the gorge where it abuts against Ordovician on the Rowsley Fault. Tillites lying on erosion surfaces are interbedded with periglacial conglomerates, sandstones and mudstones. Several tillites contain sandstone lenses and locally these are contorted. The uppermost unit contains several bands of imbricated boulders representing the residue from erosion of tillite. In the lowest band the upper surfaces of the boulders are striated which,with the imbrication, is the result of overriding by ice in a NE direction. Some granitic erratics are rotten due to Permian weathering and have been preserved during transport through cementation by ice. The Permian is cut by thin E-W basalt dykes and is overlain by terrace conglomerates of the Lerderderg R. The trace of the Greendale Fault is seen to the W. IN TRANSIT. Bacchus Marsh (50 in.). Climb out of Bacchus Marsh basin. Cross Rowsley Fault where scarp eroded by Korkuperrimul Ck.-scarp in Newer Basalt on Tertiary sediments to left - to right Bald Hill. Ascend Pentland Hills in Older Volcanics with Werribee gorge on left. LOCALITY 5 - Korkuperrimul Ck. section (59 in.). The thickest Permian sequence, described by Jacobson and Scott (1937) and Bowen (1959), dips SSW at an average of 25_35 0 (see text for description). LOCALITY 6 - Bald Hill (66m.). Post-glacial segment of Korkuperrimul Ck. section (see text for description). Morton's Quarry - fine grained sandstones showing contemporaneous slulnping and containing
78 64 Gangamopteris, overlain by conglomerate and pebbly sandstones with Notoconularia. Council Trench - Triassic conglomerates and sandstones with band containing plant remains. Return to Bacchus Marsh. LOCALITY 7 - Maddingley Open Cut/ Bacchus Marsh (69 m.). Maddingley Brown Coal Seam overlain by Tertiary sands and Quaternary gravels. The coal shows banding with at least one band of pollen coal. It contains logs of coniferous wood and pyritic concretions. A proximate analysis gives Water 610/0/ Volatiles 19%/ Fixed Carbon 17% and Ash 3%/ with calorific values of 4/245 BTU. (as received) and 10/940 BTU. (dry basis). IN TRANSIT. Bacchus Marsh (71 m.). Cross Lerderderg R. (74 m.) with outlet of Werribee R. on right. Leave basin by Anthony's Cutting - Tertiary sediments, Bullengarook basalt flow, Pleistocene sands. Djerriwarrh Ck. (76m.). Melton (80 m.). Pass Mt. Cotterill (669 ft.) on right (84m.). Return to Melbourne (104m.). by Western Highway. REFERENCES Bowen, R.L. / Late Palaeozoic Glaciations of Eastern Australia. Unpublished Thesis, University of Melbourne. Chapman, F. / Monograph on the Triassic Flora of Bald Hill,Bacchus Marsh, Victoria. Mem. Nat. Mus. Vic. / 7 : Crowell, J. C. and Frakes, L. A., Late Palaeozoic glaciation of Australia. Geo!. Soc. Aust. Jour. 17/ Edwards, A. B., Petrology of the Tertiary Older Volcanic Rocks of Victoria. Proc.Roy, Soc. Vic., 51 (1) : Edwards, A. B., The Composition of the Victorian Brown Coals. Proc. Aust.!nst. Min. Met. No. 140 : Fenner, C., The Physiography of the Werribee River Area. Proc. Roy. Soc. Vic. 31(1): Garratt, M. J., The discovery of a new Permian Marine Fauna from. Coimadai, Central Victoria, and a discussion of the palaeogeography of the glacial deposits of the area. Aust. Jour. Sci.. 32, Jacobson R. and Scott, T. R., The Geology of the Korkuperrimul Creek Area, Bacchus Marsh. Ibid., 50(1) : Parr/ W. J., The Age of the Lignite Deposits at Parwan. Min. Geo!. Journ. 2(6) : Summers, H.S., The Geology of the Bacchus Marsh and Coimadai District. Proc. Pan Pacific Sci. Congr. (Austr.), 2 : Thonlas. D.E. and Baragwanath. W Geology of the Brown Coals of Victoria. Part 3. Min. Geol. Journ. / 4(2) : Thomas, G. A., Notoconularia, a new Conularid genus from the Perm.ian of Eastern Australia. Jour. Pal. 43,
79 CHAPTER 9 65 STRATIGRAPHY AND STRUCTURE OF THE PALAEOZOIC OF WEST-CENTRAL VICTORIA by J.A. TalentandD.E. Thomas INTRODUCTION. This chapter deals with the general structural and stratigraphic framework of Central Victoria, in particular the Cambrian to Lower Devonian sequences and the Permian glacials. The Heathcote and Lancefield 1:63,360 geological maps and the Knowsley 1:31,680 geological map include important localities in the area. The 'Revised classification and correlation of the Ordovician graptolite beds of Victoria' by W.J. Harris and D.E. Thomas (1938) provides the history of prior attempts at subdivision of the Ordovician on the basis of graptolite faunas, together with the present scheme used in mapping by the Geological Survey, and applied elsewhere in the world as a subsidiary standard for zoning the Ordovician. There has been some amplification of this scheme by D.E. Thomas (1960), notably with regard to ranges of species and more extended illustration of the various forms met with. CAMBRIAN. The Cambrian occurs along the Lancefield-Heathcote-Colbinabbin belt, which is never more than two and a half miles wide. It outcrops along a general meridional direction for some seventy miles, except where transected by the Upper Devonian Cobaw granitic,massif. Small deflections to the north-west at Heathcote and to the south-west near Monegeetta are significant. The eastern boundary is a high-angle reverse fault system, made up from south to north of the Mt. William, McIvor, and Mt. Ida Faults. The Mt. William Fault brings Cambrian rocks against Middle Ordovician to Lowe r Silurian, while on the other two faults Cambrian abuts against Upper Silurian and Lower Devonian, in this case involving a stratigraphical throw of some 45,000 ft. North of the Cobaw massif the western boundary is also a faulted junction, the Heathcote and Knowsley East Faults, against Lower Ordovician (Lancefieldian and Bendigonian). To the south there is a conformable passage from Cambrian to Ordovician. The structure within the belt is extremely complex, indicated among other things by the presence of infaulted lenses of Lower and Upper Ordovician sediments. It has thus proved impossible to work out the succession in detail. The stratigraphical units recognised in the areas to south and north of the Cobaw granite are -? Middle-Upper Cambrian Middle Cambrian Lower-? Middle Cambrian Lancefield Goldie Shale s Mt. William Group Heathcote-Knowsley East Goldie Shale s Knowsley East Formation Heathcote Greenstones The Heathcote Greenstones ('Heathcotian') are altered basic to interltiediate lavas, pyroclastic s, minor intrusive s, and lenticular bedded che rts containing Protospongia sp. and Radiolaria. Their thickness has been estimated at not less than 5, 000 ft. and they are considered to be largely, if not wholly, submarine. Pillow lavas have not been recognised. The greenstones belong to the spilite-keratophyre association, being altered representatives of an original normal calc-alkaline suite characterised by an abundance of pyroxene and dearth of olivine. During the alteration, which pre-dated the main faulting,feldspars were albitised, pyroxene largely converted to actinolite, chlorite and,or talc, and secondary minerals such as stilpnomelane and the epidote group developed. Dolerite was the dominant igneous rock type, with lesser amounts of augite andesite, augite porphyrite,feldspar porphyrite, microdiorite, hornblende porphyrite, and quartz porphyrite. While many of the more basic rocks are undoubted lava flows, some at least, and most of the
80 66 more acid types. are probably dykes or sills. Small masses of talc schist are considered to be altered pyroxenite and peridotite intrusions. Two small masses of microgranite. in part albitised. outcrop within the greenstones at Heathcote. The age of these is uncertain, They may be pene-contemporaneous with the greenstones which they intrude or belong to a later period of intrusion. In general in the northern and southern portions of the belt lavas and cherts predominate while in the central Heathcote-Tooborac area pyroclastics and minor intrusives are more abundant. In this area particularly. many of the rocks have been strongly sheared during later tectonic movements. The pyroclastics. again largely altered rocks. include ashes. tuffs and lenticular agglome rate s. f I. Younger Cambrian rocks occur in two areas which for convenience are discussed separately. In the south the lavas. ashes. and cherts of the greenstone suite pass up gradationally into interbedded' cherts. black shales. and thin ash beds. As no boundary can be mapped these beds are included with the greenstones in the Mt. William Group. Some of the black shales near Monegeetta contain the rich 'dendroid' fauna listed below - Archaeocryptolaria skeatsi Chapman A. recta Chapman A. recta flexilis Chapman &: Thomas A. flabelloides Chapman &: Thomas Archaeolafoea longicornis Chapman A. monegettae (Chapman) A. serialis Chapman &: Thomas A. fruticosa Chapman &: Thomas Mastigograptus cf. gracillimus (Lesquereux) M. tenuiramosus (Walcott) M. circinalis Ruedemann. M. arundinaceus (J. Hall) Protohalecium hallianum Chapman &: Thomas cf. Chaunograptus gemmatus Ruedemann Sphenoecium filicoides (Chapman) S. discoidalis Chapman &: Thomas Cactograptus crassus Ruedemann C. flexispinosus Chapman &: Thomas C. plumigerous Chapman &: Thomas 'Acanthograptus' candelabrum Chapman &: Thomas 'Thallograptus' cf. succulentus (Ruedemann) Acrotreta antipodum Chapman Monegeetta x x x x x x x x x x x x x x x x x x Knowsle~ East x x x x x x x x x x x x x x x The overlying unfossiliferous Goldie Shales. some ft. in thickness. are black shales and mudstones. silicified in outcrop and with no ash bands. These are followed. apparently conformably. by the Ordovician. For convenience. the Cambrian-Ordovician boundary is placed at the entry of sandstones which'mark the first appearance oj abundant detrital quartz and granitic accessory minerals. One hundred feet above this the first Ordovician graptolites. Dictyonema campanulatum Harris and Keble. D. scitulum Harris and Keble. and Staurograptus diffisus Harris and Keble occur. This fauna. Zone La I of the Lancefieldian Stage. is Tremadocian in age and is correlated with part of tlw Bryograptus kjerulfi Zone of Great Britain and Scandinavia. In the Parish of Knowdey East. 6 miles N of Heathcote. the greenstones are followed conformably by the Knowsley East Formation. some 500 ft. of inte rbedded shale sand ash-bands. Be side s the 'dendroid' fauna listed above, the se beds contain two principal trilobite - bearing horizons separated by just over 100 ft. of strata. The sequence is complicated by minor folding but the field evidence indicates that the 'Dinesus Band' lies beneath the 'Amphoton Band'. The 'Dinesus Band' contains the trilobites Peronopsis sp. Dinesus ida (Etheridge f.) Kootenia fergusoni (Gregory). 'Amnhoton' sp., and fragments of a large trilobite described by Opik (1949) as Centro pleura
81 67 LEGEND III Upper Ordovician Oarriwilian &Yapeenian D Castlemainian & Chewtonian m~~~ 8~!»: [;:;:;:;:;;j Bendigonian : ~,~ Lancefieldian CjCambrian Scale of Miles Q k. 2 ~ Fig. 1. Sketch pl an of the graptolite zones of west-central Victoria (Thomas, 1939).
82 68 neglecta. In addition Chapman (1917) has recorded a number of brachiopods from this band but these are in need of revision. The 'Amphoton Band' contains Peronopsis cf. normata (Whitehouse), Dinesus sp., Solenoparia n. sp., Nepea narinosa Whitehouse, Dorypyge n. sp., 'Amphoton' sp., Fuchouia n. sp. The Knowsley East Formation passes up, apparently conformably, into the unfossiliferous Goldie Shales, which in this area are faulted against Ordovician. ORDOVICIAN. The Ordovician rocks of central Victoria have been tightly folded into a series of brachyanticlinoria and brachy-'synclinoria, or dome-like and basin-like folded structures (Fig.I). They are essentially a graptolitic facies. Their environment of deposition is little known. Turbidite deposition in bathyal or archibenthal environments, certainly below the photic zone, is the prevailing opinion. Widespread graded bedding, flow casts, unvaried lithology, near absence of neritic faunas and the presumed pelagic mode of life of graptolites have been adduced as evidence for this mode of deposition. Sediments referred to in the literature as sandstones and, in more recent time s, as greywackes, are more appropriately described as silty quartz sandstones, argillaceous siltstones, sandy siltstones and silty claystones; for much of what one would take in the field to be sandstones contain little material of grain size larger than that of silt on the Wentworth scale, and although texturally they could be described as greywackes, petrologically they differ from the typical greywacke in being low in felspar and rock chips though these are generally present in small quantitie s. Black slate s have typically 1.50/0 to 2.6% carbon with. Up to 4% potash is recorded for Victorian slates (Howitt, 1913), and their clay mineralogy is discussed by Cole and Neilson (1959). Joplin (1963, 1965) conveniently lists chemical analyses of Victorian Ordovician sediments. Arenites first appear in the succession in the Lancefieldian, and in west central Victoria are more characteristic of the Lancefieldian than of higher horizons, e. g. at Axedale where they form a prominent strike ridge. Large developments of quartz sandstones are uncommon. Graded units with simple gradation from argillaceous sandstone s to claystone or silty claystone, often with a sudden diminution of dominant grain size within the bed,are characteristic. Oscillatory graded bedding (Hills and Thomas, 1954),in which more silty units alternate with more clayey units within a broadly defined graded unit,has been explained by turbulence within individual turbidity currents, but may be due to some winnowing immediately after deposition. Small scale current bedding is widespread in the more arenaceous beds - ripple marking occurs occasionally, and structures due to peneco~temporaneous flowage are common. It had been suggested that the occurrence of graptolites (assumed pelagic) within these graded units could be due to the graptolites being killed by turbid water in the upper parts of turbidity currents, captured by the flow and then sinking with the finer fraction. Graptolites. are certainly extremely rare within the arenaceous parts of these units, but if they were deposited by the method suggested one would expect that occasionally they would be found lying at an angle to the bedding planes. They have never been found in such a position as indicators of bedding directions. In fact the method of their burial is not well understood. Benthonic fossils are so rare as to be of little significance for correlation but are important as environment indicators. Phyllocarid crustaceans are abundant at many horizons and occur from time to time at most graptolite localities; their ecological significance is not known. Linguloid brachiopods, though rare, have been found at many localitie s throughout the graptolite facie s. The presence of many of them may be due to transport and perhaps growth within floating masses of algae which subsequently foundered or dropped their contents. An appreciable variety of chitinous brachiopods (Lingulella, Obolis, Palaeglossa, Schizambon, and acrotretids), invariably poorly preserved hyolithids and nautiloids (Thomas and Teichert, 1947; Talent, 1959), sponge spicules and crinoid ossicles (e. g. Bald Hill, Parish of Waratah) are the most usual forms; gastropods, corals and trilobite fragments are extremely rare. The occurrence of tabulate and rugose corals, brachiopods, crinoids and molluscs in the sandstones of the Riddell Grits (Gisbornian and Eastonian) of the Riddell-Sunbury district is exceptional. The contained neritic faunas are almost invariably comminuted, testifying to dumping; they are not therefore indicators of depth. I,
83 Fig. 2. Geological map and section of Bendigo Goldfield and plan of main axial lines (Thomas, 1953). '
84 70 Directional studie s on sedimentary structure s and graptolite s indicate source s to the we st and to the south-west (N. W. Schleiger, personal communication). North of the Harcourt and Cobaw batholiths. The Whitelaw Fault (Harris, 1934), striking about N 15 0 W, and traced for some 14 miles N of the granodiorite, divide s this area in two; to the west is the Bendigo goldfield, to the east, on the downthrown side, the poorly auriferous 'Strathfieldsaye Trough' (Thomas, 1939). The Whitelaw Fault has a displacement of about 12,000 ft. ve rtically according to Harris, bringing Upper Darriwilian beds to the east into contact with Lower Lancefieldian beds to the west. Harris (1935) has recorded post-pliocene movement along this line, with dislocation of surface gravels at Ironstone Hill near Huntly, and of the Huntly Deep Lead. This compares with similar late Tertiary movements on the parallel Muckleford Fault to the west except that on the Whitelaw Fault movement was insufficient to shear the Harcourt Granodiorite (Thomas 1934; Beavis 1963). The Bendigo Goldfield. The Bendigo goldfield (Fig. 2) is now regarded as a minor synclinorium on the western flank of a Inajor anticlinoriuin in which the oldest (Lancefieldian) beds outcrop adjacent to the Whitelaw Fault. The iinportant 'lines' of saddle reefs lie on the western flank of the major anticlinorium (Fig. 1); strike faulting (cf. HerInan, 1923) is no longer considered structurally important. A sinall anticlinoriuin to the south-west of Bendigo is set askew to the major structure s of the area. The detailed structure of the Lower Ordovician of the Bendigo field is known from surveys of mine workings, 2 mines being over 4,000 ft. and 115 over 2,000 ft. deep.. This detailed information has been important for interpreting the structure of adjacent areas known principally from surface mapping. The field was worked for a length of over 15 miles. Rich quartz 'saddle' reefs were quickly found to underlie each other along the axial lines of anticlines (as many as 24 successive saddles being found in one mine) which led to prosp.ecting by nuinerous deep shafts and short crosscutting. More than 20 major anticlines occur within the productive belt (3 Iniles wide) and strike about The axial plane s generally list slightly to the east in depth, although this listing may be due at least in part to strike fauiting with sinall predominantly easterly movements, displacing essentially vertical fold axial planes (Stone, 1<;31). The axial lines of the folds are fairly parallel, recurring about 10 chains apart; most of them persist for miles, sometimes bifurcating. sometimes dying out. the folds typically die out as 'rolls' in the steeply dipping limbs of adjacent lines. Minor folds develop in places between main lines, with rapidly varying pitch (plunge). bouble and tripie folding of centre country has been known to occur on some lines in various places. Reversals of pitch lead to doinal structures aiong the various anticlines. These occur diagonally but irregularly across the field. the dotyles on adjacent lines being out of alignment. The location of pitch reversals in the synclines is less well known, but at tiines the pitches on adjacent synclines and anticlines are not in the saine direction. Some lines. e.g. the Garden Gully, exhibit two domes and a trough along their worked length. The richest mines were often associated with these domes, esp.ecially in the vicinity of the change to a northerly pitch. Individual folds are sharp with liinbs for the most part dipping uniforinly at 65 0 to 75 0 but the form of the anticlines varies considerably from foid to fold, and at different horizons in the same fold, owing to differing competence of strata. Construction of sections is difficult because stratigraphic horizons cannot usually be traced across neighbouring folds with certainty. Rock flowage of the less competent strata was assuined by Herman (1923) to have given rise to thickenings over the anticlines equal to two and a half times the thickness of the limbs, but Stone (1937) suggests this thickness is considerably greater, up to four or six times. Hills (1963) regards the folding as concertina or chevron type with rotation only of the limbs about median planes; the net result is production of essentially similar type folds in which the volume remains constant and the beds retain their original thicknesses, apart from relatively minor effects at crests and troughs where deforination is concentrated. The several major 'strike faults' of Herman's sections are not supported by the evidence of later mapping; the discrepancies found when matching zones across several lines of folds are -now..
85 71 attributed to asymmetry in folding. combined with minor strike faulting on individual lines. These minor strike faults are numerous and are commonly bedded; where they are bedded. laminated quartz commonly occurs along the fault planes. forming the 'legs' and 'backs' of the reefs. Characteristically these occur in pairs at the same stratigraphic position on opposite sides of the fold. meeting at the turnover. where one is commonly cut off and dragged by the other; the stronger fault displaces the anticlinal axis. and continues upwards across the bedding. flattening in dip to about 45 0 and forming the 'neck' of the saddle reef. :Major strike faults continue to the next syncline (where they again become bedded). and may displace centre country up to 100 feet; minor ones die out. many of them displacing centre country less than 3 feet. East dipping faults appear to predominate over west dipping. Stone explains the fault pattern by rock flowage in the limbs of folds (where the steeply dipping attitude of the beds permits yielding by flow under compression) and relatively greater competence at the crests. where the end-on attitude re sult s in failure by (strike) faulting. Oblique faults or crosscourses are much less frequent. and only a few of the stronger. such as Collman's crosscourse. persist across the neighbouring anticlines. The latter crosses at least five anticlines and has a lateral displacement of about 20 ft., with prominent drag of strata on either side of the fault plane and great local enrichment of the reefs. Thin monchiquite dykes. of the order of 3 to 10 ft. thick, are frequently associated with the centre country. typically following the axial planes though wandering to the limbs or turning along oblique faults in places (Stillwell. 1911, 1918). They fill later fractures and are regarded as probably Tertiary in age (Stillwell, 1912; Edwards, 1938). East of the Whitelaw Fault - the Strathfieldsaye Trough. The Strathfieldsaye Trough (Thomas, 1939) contains the youngest Ordovician rocks of the district. outcropping along the east side of the Whitelaw Fault. These were described by Harris (1935). who subdivided the then 'Darriwilian' by means of the abundant diplograptid fauna and established the basis for the present zoning - Yapeenian 2 + Darriwilian Da 1-4 (=M.O. 1-4). formerly Da~riwilian D 1-5. The present account incorporates results of subsequent mapping by geologists of the Geological Survey of Victoria. This has considerably modified the zoning by Harris. which was based on collections and mapping by J. J. Caldwell. Reversed faulting, forecast by Harris, is more important than on the Bendigo Goldfield. It is a maj~r factor in the formation of the Strathfieldsaye Trough (G. J. Medwell, personal communication). Enclaves of higher and lower zones occur frequently in the broader belts of predominantly uniform age, and are found whenever sufficient fossil outcrops can be located. They are attributed to the sharpness of individual folds combined with alterations of pitch north and south along the strike of the fold axes, and also to local flexures in the overall anticlinorial or synclinorial structure. A few may be the result of strike faulting. The Strathfieldsaye Trough shows a superficially normal succession of zones eastwards from the Whitelaw Fault. from Darriwilian at the fault to Lancefieldian towards the Campaspe River. Generally the strikes are northerly in the southernmost parishes and 15_20 0 W of N in the northerly parishes, but occasionally are locally NW or W. The trough is bounded on the east i. e. near the Campaspe River, and on the west i. e. west of the Whitelaw Fault, by Lancefieldian beds mapped by several workers, notably J. J. Caldwell and F. Chambers, and more recently by G. J. Medwell, particularly along the Eppalock - Bendigo pipeline. The eastern belt of Lancefieldian is known only from the pipeline and scattered graptolite localities in Eppalock and Axedale. The western belt terminates southwards in Sedgwick where Bendigonian and Chewtonian beds are faulted directly against Darriwilian just north of the granite contact. The Lancefieldian beds are less frequently fossiliferous than the higher zones, and are often greenish in colour; black fos siliferous slates and nodular magnesite are common near the Whitelaw Fault. The Campaspe Lancefieldian beds are succeeded westwards into the Strathfieldsaye Trough by middle Bendigonian (Be3). Lower subzones (Bel-2) with the distinctive incoming 'burst' of,i. fruticosus (4 branched form) are absent. Above Be3, the Be4 subzone appears very narrow. of the order of 200 ft. (maximum), and the 4-branch form may here continue to'the top of the Bendigonian together with the 3-branch form (G. J. Medwell. personal communication).
86 72 Chewtonian beds occur in apparently normal succe ssion we st of the Bendigonian in the parishes of Lyell, Eppalock, Axedale and Wellsford, although some faulting between the zones seems likely. Castlemainian succeeds Chewtonian westwards in these parishes as a narrow belt. The Yapeenian, extending as a broad belt through Sedgwick, Strathfieldsaye, Wellsford and into Huntly contains many included areas of upper or lower zones, especially in Wellsford and Strathfieldsaye (but this merely reflects more intense fossil collecting). Its contact with Castlemainian on the Eppalock pipeline is faulted, but the sequence westwards into Darriwilian beds is apparently normal. Darriwilian beds are extensive in the same parishes and are richly fossiliferous (Harris 1935). Axe dale - He athc ote The broad belt of Lancefieldian rocks east of the Strathfieldsaye Trough is joined near the Ca.rnpaspe River by the NW trending belt of Lancefieldian beds lying south and west of Heathcote (Thomas, 1939). The trend of this belt parallels the faulting of the Heathcote-Colbinabbin axis. A small trough containing a fringe of Bendigonian around a small patch of Chewtonian is developed.west of Toolleen South of Axe dale the pitch is to the Sand interdigitations of Bendigonian are succeeded further south by Chewtonian and Castlemainian; minor structures can be recognized, for example a domal area near Redesdale, and southwest of Lyell, and the trough-like structure near Mia-Mia. Southwards towards the Pyalong massif, Castlemainian and Chewtonian beds are developed particularly in the parish of Glenhope where they are notably fossiliferous (Thomas MS). They are flanked on the east and west by older b~ds delineating a possible northwards extension of the Riddell Trough. Enclaves within the Heathcote-Colbinabbin Axis. Detailed map.ping by Thomas (1940, 1941, 1965) of the parishes of Crosbie, Knowsley East and Heathcote has delineated a complex series of faulted slice s of Lancefieldian to Upper Ordovician sediments; the structure is doubtless more complex than has been mapped, but exposures are poor. Three adjacent fault slices in Knowsley East consist, west to east, of Bendigonian or basal Chewtonian faulted against Darriwilian (DaZ-3), faulted against Chewtonian (Chl-Z-3), Castlemainian (Cal-Z-3) and possible Yapeenian (Ca3 or Yal). Further north is a slice or slices of Lancefieldian (t.az, La3) and Bendigonian (including Bel). Slices of Darriwilian (DaZ - 3) and Castlemainian (CaZ) occur to the south, and Upper Ordovician is infaulted among outcrops of Cambrian pyroclastics along McIvor Creek 1 Yz miles north of Heathcote. Individual graptolite zones within these Ordovician enclaves appear to be thinner than usual, though this may be due to faulting. They lack the sandstone beds characteristic of the adjacent Lancefieldian sediments to the west, and, as a generalization, appear to be finer grained and to have more black slates and cherty sediments than those away from the Cambrian axis. This area therefore appears to have been a 'high' during deposition of the Ordovician sediments, thereby receiving a condensed sedimentary sequence. Between the Muckleford and Djerriwarrh Faults. Earlier work in this belt was not carried out from the point of view of the stratigrapher or palaeontologist. The literature is voluminous, but Harris and Thomas (1934) have indicated the stratigraphically important papers and geological maps for the area north of the main divide and list graptolite localities important for understanding the regional structure of this area. Thomas (1939) modified by Harris and Thomas (1949) gives the current publish~d synthesis of the structure south of the main divide. The bibliography of Gregory (1907) is the key to the older, essentially economic, liter~ture. Towards Castle maine there is a descending sequence as the Chewton-Blackwood Anticlinorium is approached (Hall, 1895; Baragwanath, 1903; Harris, 1916). Mapping of the Castlemaine-Chewton goldfield (Baragwanath, 1903) has shown the regular repetition of anticlinal axes at intervals of approximately 850 ft.; basic dykes are commonly associated with the anticlinal axe s. The usual monotonous clastic sediments of the Victorian Ordovician have belts of silty sandstones up to 50 ft. in width and belts of slate up to 100 ft., e.g. the Wattle Gully slates
87 73 (Thomas et ai., 1935). In the north of the goldfield the sediments are metamorphosed to hornfels for up to 7/Sths of a mile from the boundary of the Harcourt batholith. Lithologic oddities include beds of unfossiliferous, possibly metasomatic, white limestone encountered in the Specimen Reef Company workings, and cone-in-cone calcareous beds encountered in the Francis Ormond Mine at Chewton; the latter recalls similar occurrences in the Bendigo goldfield. Use of graptolite assemblages as a tool in remapping the Chewton goldfield (Thomas, Mulvaney and Whiting, unpub.) has enabled a refined delineation of the pattern of folds and faults and shows graphically the effect of changing pitch along the fold axes. The folds in this area are asymmetric with near vertical or slightly overturned limbs (Thomas, 1940). The Chewton-Blackwood Anticlinorium is succeeded on the west by the Expedition Pass Trough where the highest beds have yielded Yapeenian (Yal) graptolites (Harris and Thomas, 1934). These beds are succeeded to the east by a descending succession until the broad belt of Lancefieldian beds occupying the Lauriston-Taradale Anticlinorium or Dome is reached. There are 17 scattered localities in this belt that have yielded Lancefieldian (La2) assemblage s, from Tylden in the south to between Taradale and Elphinstone in the north. Most of the information for the age of this belt has been obtained from the dumps of alluvial mines penetrating late Cainozoic basalts to the bedrock beneath. Outcrops north of the Macedon igneous complex are poor, but Harris and Thomas (1934) refer to numerous Darriwilian (D2-3) localities along the Carlsruhe-Lancefield road. Thomas (1939) refers to Darriwilian beds in the vicinity of Woodend being surrounded by Yapeenian beds; the term Woodend Trough has been used for this structure. Sunbury-Maribyrnong River and the Ordovician-Silurian boundary west of Melbourne. Upper Ordovician sediments are exposed westwards from Gisborne as a series of inliers along the valleys of Jackson, Emu, Konagaderra and Deep Creeks. Though much of the area is masked by late Cainozoic basalts, a broad structural pattern has been discriminated (Thomas and Keble, 1933) in which the southerly continuation of the Mount William Anticlinorium can be recognized flanked by latest Darriwilian-early Upper Ordovician (Gisbornian) sediments, best known from the richly fossiliferous graptolite locality at the junction of Jackson and Riddell Creeks. This str'ucture is succeeded eastwards by the Clarkefield Synclinorium with a development of Eastonian beds in the south, and the Sunbury Anticlinorium in which Gisbornian beds reappear; the area is closely and sharply folded with evidence of faulting. Farther to the west is the Sunbury Synclinorium with Eastonian beds and an occurrence of Bolindian beds on Emu Creek, the Diggers Rest Anticlinorium where Gisbornian beds reappear, and the much broader Bulla Synclinorium in which Eastonian and Bolindian beds are succeeded eastwards by early Silurian (Llandovery) sediments. Structures throughout the area trend NNE to SSW. The Upper Ordovician rocks of this area consist of generally thin-bedded shales, silty claystones and silty sandstones with occasional massive quartz sandstones and pebbly sandstones (the Riddell Grits mentioned above). The latter occur at several horizons from middle Gisbornian to Eastonian, frequently contain fragmentary shelly fossils, and tend to form strike ridges where they outcrop from beneath the basalt cover. Poorly preserved trilobites, chonetid and rhynchonellid brachiopods, pelmatozoans (Chapman, 1932) and undescribed orthoid brachiopods and rugose corals occur in association with graptolites indicating a horizon about that of Climacograptus peltifer and Diplograptus multidens (Gisbornian). Orthograptids occur in abundance in some horizons of the Eastonian, with dicranograptids occurring in abundance high in the Eastonia~ at Emu Creek, similar to their occurrence in the type area for this stage at Mt. Easton (see below); Bolindian sediments in this area are typically thin bedded, variegated, often bluish grey silty claystones, clayey siltstones, silty sandstone s and shale s becoming sparingly fossiliferous higher in the sequence. A lithologic change to distinctly olive-green clayey siltstone s and silty sandstone s corre s ponds roughly to the Ordovician-Silurian boundary; it has been given considerable weight in drawing a provisional boundary on Emu Creek, along Deep Creek for some miles north and south of Konagaderra and westwards from Darraweit Guim. An actual line of contact cannot be seen at any of these localities, but can be fixed within a chain or two. The lithological change takes place rather abruptly, though the change is progressive. Despite the more crumpled nature of the Upper Ordovician in contrast to the more gently folded nature of the Silurian, the two systems have all the appearances of being conformable, though a slight break of disconformity may be present. The contrast in degree of deformation between the two systems has been attributed to lithological differences (Thomas and Keble, 1933). The diastrophism in eastern Victoria at this time seems to be reflected solely by a change in lithology in this part of central Victoria.
88 74 A pronounced northward pitch is indicated by the occurrence of Bolindian strata along Konagaderra Creek in the parish of Darraweit Guim and by the restriction of Ordovician sediments to the core s of anticline s exposed in the W -E tract of Deep Creek upstream from the township of Darraweit Guim. Beds thought to be conformable with Late Ordovician graptolitic sediments at Darraweit Guim contain a surprising abundance of undescribed smalliamellibranchs with occasional hyolithids, trilobite s, gastropods and nautiloids, succeeded by dense homogeneous blue-grey clayey siltstones with a comparative abundance of trilobites, mainly Zeliskellinae; these beds may be of basal Silurian age. The structure west and northwest of Darraweit Guim. is not well known; the anticlinoria and synclinoria seen farther south have not been well located 'owing to the basalt cover. It would seem however that the Ordovician strata outcropping in anticlines near Darraweit Guim are on the Diggers Rest Anticlinorium and that the strata farther west are within the Sunbury Synclinorium. to as far as the Surprise Gully Fault where the Lower Silurian sequence is faulted down against Bolindian sediments. The same belt contains Gisbornian graptolites in Surprise Gully as well as a slice of Darriwillian sediments adjacent to the Mount William Fault. SILURIAN AND EARLY DEVONIAN. Silurian and Lower Devonian sedimentary rocks are not found west of the Lancefield Heathcote-Colbinabbin Cambrian belt. The succession appears to be conformable from Ordovician to Silurian in the valleys of the Maribyrnong River and Jackson's Creek, but these exposures are neither readily accessible. nor abundantly fossiliferous. Heathcote-Redcastle District. Prior to the work of Thomas (1937; and parish plans 1940, 1941) the Silurian-Lower Devonian sequence was assumed to rest unconformably on the Cambrian rocks in the W with younger horizons appearing eastwards, but mapping has shown that the oldest horizons outcrop in a dome about Costerfield with younger horizons tending to occur as annuli around it. The youngest horizons occur to the northwest adjace~t to the Mt. Ida fault in the parishes of Redcastle and Cornella with a distinct synclinal structure being still in evidence about Mt. Ida. The succession is as follows - 1. Costerfield Formation is at least Z,OOO ft. of greenish siltstones and thin silty sandstones, the former generally displaying 'fucoid' markings; no identifiable fossils have been found apart from rare crinoid ossicles and an indeterminate trilobite. Z. Wapentake Formation is about 5,000 ft. of terrigenous sediments whose base is defined by a thick silty claystone to clayey siltstone, the 'nlaenus' Band, characterized by nodules which some consider to be organic. The most prominent fossils are species of Thomastus and the brachiopod Meifodia tyro (Opik). A large number of other trilobites, brachiopods, gastropods and ostracodes have been described by Opik (1953). The 'Illaenus' Band is succeeded by a sequence in which mudstones predominate,overlain by a sequence in which sandstones predominate. 3. The Dargile Formation is likewise about 5,000 ft. in thickness. It has been divided into four units: (i) the lower beds consisting of unfossiliferous mudstones; (ii) the graptolite beds which have yielded Monograptus bohemicus, M. colonus var. compactus, M. varians, M. uncinatus var., M. aff. nilssoni (Harris &. Thomas 1937) and a species of Dictyonema (Harris &. Thomas 1941). (This unit has yielded a number of eurypterids, carpoids and starfishes as well as a range of rhynchonellid, dalmanellid and spirife rid brachiopods. ) (iii) the Dargile Sandstone s. a well defined horizon of typically unfossilife rous sandstones becoming more fossiliferous towards the top; and (iv) 'Chonetes-Encrinurus' Mudstones, a unit characterized by association of Acgiria thomasi and Encrinurus simpliciculus, which is widely distributed from Baillie ston to Wallan. 4. McIvor Formatior. is 3.bout 5,000 ft. of fossiliferous sandstones characterized by an abundance of rhynchonellids. especially Stegeirhynchus-like forms. the rhynchonellids Molongia. a wide range of bivalve s and occasional homalonotid trilobite remains.
89 75 5. Mt. Ida Formation is about ft. of predominantly arenaceous sediments resembling those of the McIvor Formation. and divisible into four units - (i) (U) (iii) (iv) the Molongia Beds; the Notoconchidium Beds; the Pleurodictyum-Strophonella Beds; and conglomeratic mudstones with interbedded mudstones developed near Mt. Camel and in the western part of the parish of Dargile adjacent to the Mt; Ida Fault. The shelly faunas of the Heathcote district have been recently monographed (Talent 1965). The nearer shore McIvor and Mt. Ida Formations pass eastwards into graptolitic sediments about Seymour. The Mt. Ida Formation is very early Devonian in age, but owing to poor preservation and the nondescript nature of its faunas it is uncertain how much. if any. of the McIvor Formation is Silurian and how much is Devonian. Lancefield District. Three stratigraphic units have been discriminated in the Silurian sequence east of the Mt. William Fault. separated from each other by prominent marker horizons. viz: 1. the Deep Creek Beds separated by a prominent conglomerate from the overlying 2. Springfield Beds, about ft. of sandstones and siltstones including Upper Llandovery graptolites. terminated by a well developed sandy horizon containing an abundance of?wenlock trilobites. brachiopods and gastropods, mainly undescribed species; and the 3. Chintin Beds. which are defined as lying above the aforementioned sandstone. but a top for this formation has yet to be decided on. If it is taken to extend up to the graptolite beds of the Kilmore district it embraces equivalents of Unit 1 of the Dargile Formation at Heathcote. A more convenient and mappable horizon in this district is the Clonbinane Member, the equivalent of the base of the McIvor Formation. If the Chintin Beds were defined in this way they would embrace equivalents of all units of the Dargile Formation as typically developed in the Heathcote district. PERMIAN. Permian glacial and fluvio-glacial sediments occur sporadically in central Victoria, and glacial pavements are exposed at their margins. Sediments and pavements will be seen at Localities 27 and 28, and are described under these localities in the itinerary. ITINERARY FIRST DAY Proceed froitl Melbourne to Lancefield across Late Cainozoic volcanics (see Ch. 11). LOCALITY 1. A generally asc.ending sequence through the Mt. William Group to the Goldie Shales occurs in road cuttings on the Lancefield-Kilmore road and in old railway cuttings. Che rts and ashe s with some interbedded diabase pass upwards with apparent conformity into unfossiliferous black slates and cherty shales of the Goldie Shales. The coarse 'diabases', formerly dolerites. occurring to the Nand S and dominating the lower part of the Mt. William Group, are not present in this section. Protospongia is to be found in cherts here within the Mt. William Group; farther S traces of hydroids have been found and at a locality 2 m. ENE of Monageeta abundant hydroids have been found in black shales at about the same horizon. LOCALITIES The Mt. William Group is faulted on the E against the Lower to Middle Silurian Deep Creek. Springfield and ChintinBeds. Farther S, near Springfield. Upper Ordovician mudstones. sandstones and grits occur in a fault slice or slices on the W side of the Mt. William Fault. A small fault slive r in Surprise Gully contains Darriwilian graptolite s adjacent to an acid dyke
90 76 Fig. 3. Position of localities in itinerary.
91 77.. (Loc.2). Gisbornian graptolites of the zone of Nemagraptus gracilis can be collected S of this fault sliver (Loc. 3). LOCALITIES 4, 5, 6, 7. These form a short sequence through the Ordovician-Silurian boundary along Deep Creek (Maribyrnong River). Bolindian sediments with Leptograptus eastonensis, Retiograptus pulcherimus and Climacograptus uncinatus will be seen at three localities (4,6,7). These are faulted against Silurian sandstones and shales of the Deep Creek Beds. Early Silurian (Keilorian-Llandovery) fossils can be obtained from drab olive green splintery shales (5). LOCALITY 8. Middle Cambrian hydroids in black shales of the upper Mount William Group (listed in text). LOCALITY 9. This is shown as localities 45 to 47 on the Lancefield Geological Map, having well preserved Bendigonian Be 2 graptolites, the assemblage being characterized by four-branched Tetragraptus fruticosus with the abs,ence of T. approximatus and three - branched T. fruticosus. LOCALITIES 10, 11. At Stauro Gully are sandstones with black cherts and cherty shales containing Staurograptus diffissus, Dictyonema campanulatum, D. scitulum, phyllocarids and occasional inarticulate brachiopods. The se beds are separated by about 1,000 ft. stratigraphically from the next Lancefieldian La 2 horizon occurring in Stauro Gully just above the road (Locality 68 of the Lancefield map and 11 of this excursion). The La 2 zone is characterized by a burst of Anisograptidae including Adelograptus (A. victoriae,.b clarki,.b antiquus inter alia) formerly referred to under the generic name Bryograptus, and Clongraptus (C. tennellus,.. rigidus, C. magnificus,..:. flexilus ). Tetragraptus decipiens, two primitive species of Didymograptus, D. taylori and12..: pritchardi, and two large species of Dictyonema, 12.:. pulchellum and D. magillivrayi appear in this zone. The same succession of La i to La 2 occurs in Bryo Gully to the N (Localities 62, 65, 71 and 48 of the Lancefield map). LOCALITY 12. La 3 beds here are characterized by a similar fauna to the preceding La locality but marked by the incoming of large forms of Tetragraptus, T. approximatus and T. acclinans. LOCALITY 13. The Lancefield Quarry is the type locality for the Lancefield Beds of T. S. Hall. The quarry. na,s.not been'worked for many years and is no longer a worthwhile collecting spot. It is 1&ta:te'd ~n allotment 56A, 2 m. NE of Lancefield. l,. LOCALITiES 14, 15. In the N of this area there is an ascending sequence through Bendigonian, Chewtonian, Castle.'il'!'a!j,nian and Yapeenian horizons to Darriwilian zones 1 to 3. The transition from Bendigonian Be,4 to, Chewtonian Ch 1 may be investigated on the Pyalong road about 2 m. NNE of Lancefiel;L',:,:rhe base of the Chewtonian is mapped by the incoming of the dependent species of Didym:ograptus, particu1arly.q.. protobifidus, and the survival of 3-branched T. fruticosus. Ch 3 horizons are characterized by the disappearance of T. fruticosus and with persistence of.q:. proto bifidus. LOCALITIES 16, 17, 18, 19, 20. These are a series of trenches in representative Cast1emainian, Yapeenian (Ya 1 and Ya 2) and Darriwilian horizons about 3 m. N of Lancefield. IN TRANSIT. Depending on time available it may be possible by a detour of about 20 m. to visit Willey's Quarry S of Woodend, a locality famed for its Yapeenian graptolites (Ya 2). Among the more notable forms are: Dichograptus octobrachiatus, Tetragraptus guadribrachiatus, L ~, Phyllograptus sp., Coniograptus speciosus, Trigonograptus ensiformis, Didymograptus ~-def1exus, Isograptus caduceus,..h dumosus,..l- manubriatus, Skiagraptus
92 78 gnomonic us, Oncograptus upsilon, Cardiograptus morsus, Maeandrograptus tau. Otherwise the excursion can drive direct from Lancefield 45 m. to Harcourt. Most of the route from Lancefield to Elphinstone lies acrosslate Cainozoic basalts covering deep lead systems. Some of these were worked for gold. the workings being indicated by mullock dumps beside the highway. From Elphinstone to Harcourt the route lies within the Harcourt batholith (Beavis, 1964). The geology of the adjoining Castlemaine-Chewton area is' described in Chapter 10. LOCALITY 21. SECOND DAY The Harcourt Granite Quarry is one of a number of quarries in the district which have produced commercial 'granite'. Here evidence of flowage is provided by abundant schlie ren; these and the relatively abundant xenoliths which tend to occur in pipe-like arrangements often detract from the beauty of the stone. LOCALITY 22. At Big Hill, 7m. S of Bendigo, contact metamorphism is seen along the northern margin of the Harcourt Granodiorite. The zonal sequence northwards from the granodiorite is, according to F. C. Beavis (1962). 1.. cordie rite hornfels, 2. biotite andalusite hornfels, 3. spotted slate, and 4. normal siltstones and silty sandstones of Castlemainian age. LOCALITY 23. At the Whitelaw Fault on the McIvor Highway, Darriwilian rocks outcropping within the Strathfieldsaye Trough on the E are faulted down against Lancefieldian rocks on the W; the fault line having little or no surface expre s sion except for a strip of reef quartz. LOCALITY 24. A typical Bendigonian Be 3 horizon at Specimen Hill with Tetragraptus fruticosus 3 and 4 branched varietie s occurring in as sociation with the absence of 1.: approximatus. LOCALITY 25. A Darriwilian Da 2-3 horizon at Brick & Pipe Industries pit. McIvor Rd. LOCALITY 26. Permian till in a roadcutting in the McIvor Highway at Derrinal. Few of a wide variety of igneous, metamorphic and sedimentary erratics can be positively matched to their source. with the exception of fairly abundant reddish sandstone s which may well have come from outcrops of the Grampians Group (Upper Devonian) in western Victoria. A single large boulder of Mt. Ida Formation containing early Devonian fossils was formerly found beside the old highway in the vicinity of Mt. Ida Creek. indicating some ice movement from the E, NE or SE in early Permian times. This is the reverse direction of the regional ice movement towards the ENE indicated by an abundance of blocks of fossiliferous Mt. Ida Formation in Pe'rmian glacial deposits about Wangaratta, Greta. Springhurst and Peechelba in north-eastern Victoria. LOCALITY 27. A series of glacial pavements exhumed by the waters of Eppalock Weir and by the activities of the Bendigo Field Naturalists Club, particularly Mr. Frank Robbins who has devoted a lot,
93 79 of time to excavation and recording of the pavements by stereo photography. Due to wetting and drying with the rise and fall of the weir, the pavements are deteriorating quite rapidly. The striations on these pavements indicate ice movement generally from the S, but evidence from glacial striation and gouging (see also evidence from the Bacchus Marsh area, Chapter 8 ) and from regional transport of readily matched blocks indicate that the direction of movement of ice was not constant. LOCALITY 28. Fluvio-glacial sandstones, including lithic sandstones, till and tillite exposed in a cliff section beside the Eppalock Weir, Knowsley, about a mile E of the Meadow Valley Fault. The distribution of the Permian glacial and fluvio-glacial sediments in the Knowsley East Derrinal-Langwornor district is dictated in part by faulting approximately parallelling the fault system delineating the Cambrian rocks of the Heathcote-Colbinabbin axis, but elsewhere the boundaries are quite irregular with Permian land surface being exhumed, as for instance about Dunn's rock and southwards from Derrinal. LOCALITY 29. Clays and gravels stratigraphically older than the Newer Volcanics of the CaITlpaspe River valley include valuable deposits of light green clays at Axedale on either side of the McIvor Highway. The clay has been used for bricks, tiles, earthenware pipes. sanitary ware and general pottery ware. It has been worked by shaft and open cut methods. THIRD DAY The Silurian to Early Devonian sequence =ay be exaitlined in stratigraphic sequence froitl the Costerfield Dome to the highest beds in the parish of Redcastle. LOCALITY 30. Costerfield Formation is exemplified by sediments mined from the Costerfield Shaft. showing 'fucoidal' markings. These are the oldest beds in the Silurian succession of this area. LOCALITY 31. The 'Illaenus' Band at locality F44, parish of Heathcote. This is a rich locality for this horizon, the dominant forms being Meifodia tyro, Thomastus thomastus. Raphispira? latens and Ctenodonta sp. Attention is drawn to the hollow nodules (?coprolites) characteristic of this horizon; Dr. A.A. Opik (1953) has argued for an elasmobranch origin of these objects. LOCALITY 32. A small quarry in sediments of Unit 3 of the Wapentake Formation. Silty sandstones predominate over mudstones in this unit. LOCALITY 33. Localities F42 and 43 in the graptolite beds (unit 2) of the Dargile Formation. This locality has yielded the carpoid Victoriacystis wilkinsi, the eurypterid Melbournopterus crossotus. an abundance of the ophiuroid Urosoma glabridsicus, together with a number of brachiopods and graptolites (see general text). LOCALITY 34. Unfos siliferou6 sandstones of unit 3 of the Dargile Formation exposed in the road cutting of the Heathcote-Costerfield road. Mudstone s of unit 4 of the Dargile Formation containing the characte ristic Aegiria thomasi and Encrinurus simpliciculus. This locality will embrace localities F 47 and 48 of the parish plan of Heathcote.
94 80 LOCALITY 36. Because of the poor pre servation of most fossils from the McIvor Formation only a single locality will be visited, locality 20 of the Heathcote parish plan. The more important elements are an undescribed species of Molongia, a wealth of rhynchonellids, gastropods including bellerophontids; loxonematids and tropidodiscids. LOCALITY 37. Sandstones high in Unit 1 of the Mt. Ida Formation containing abundant rhynchonellids together with species of Atrypa, Lissatrypa, Leiopteria. Once again, as with the McIvor Formation, poor preservation has hindered determination at the specific level. LOCALITY 38. The incoming of the cuboidal rhynchonellid Notoconchidium in abundance, the zone fossil of Unit 2 of the Mt. Ida Formation, is here exemplified a few chains downstream and stratigraphically higher than the preceding locality. These two localities are F 53 and F 52 re spectively, parish of Redcastle. LOCALITY 39. Typical richly fossiliferous Unit 3 of the Mt. Ida Formation, this locality has yielded a wider range of species than any other Silurian or Lower Devonian locality in the Heathcote-Redcastle district. Prominent forms are Pleurodictyum megastoma, Stropheodonta limbimura, Tyersella, Maoristrophia sp., Molongia sp., Atrypa sp., Lissatrypa sp., Macropleura corvus, Conocardium sp., Gravicalymene sp. and an acastid trilobite. This is locality F 25. LOCALITY 40. The highest beds of the Mt Ida Forma'tion, consisting of mudstones, shales and conglomerates, are rarely fossiliferous The Mt. Ida Formation does however contain other lenticular bodies of mudstone which rarely outcrop' Typical of these is locality F 26, parish of Redcastle, in Unit' 2 of the Mt Ida Formation. This has yielded a number of bivalves and fragments of trilobites including an undescribed genus of blind proetid, but the locality has yet to yield adequate materials for specific determination of any species. LOCALIT Y 41. Enclave s of Ordovician sediments faulted into the Heathcote Greenstone s in the vicinity of Mt. Camel. Two meridional slivers of Upper Ordovician sandstones and slates are joined by a patch of Chewtonian sandstone s and slate s. Graptolite s will be collected from each of the se horizons, and a visit made to an aboriginal quarry on the slopes of Mt. Camel. Such infaulting of slivers of Ordovician sediments is characteristic of the Heathcote-Colbinabbin Cambrian belt and is a constant reminder of the enormous structural complexity of this 'axis'. FOURTH DAY LOCALITY 42. This is a succession of localities in the vicinity of Lady's Pass and the junction of the Toolleen and Colbinabbin roads. A sequence of interbedded Cambrian lavas, tuffs and agglomerates is well exposed in the bed of Lady's Pass Creek near the derelict Lady's Pass wine shanty. Similar lavas and pyroclastics together with green cherts occur on the hillside opposite the junction of the two roads and extend northwards towards Lady's Pass where an infaulted body of contorted cherts occurs. The diabases are distinctly schistose adjacent to the fault. The cherts are remarkably contorted with folds pitching as much as 85 0 and even overturned. LOCALITY 43. A traverse along 'Trilobite Gully', parish of Knowsley East, to show the two trilobite-bearing horizons in the Knowsley East Formation (see general text). The sequence includes sediments containing reworked pyroclastic materials, including one prominent unit resembling an agglomerate. Upstream from the trilobite horizons there follows an orderly succession into the Goldie I
95 81 Shales, which is faulted against Castlemainian and Yapeenian sediments faulted in turn against Heathcote Greenstones. LOCALIT Y 44. A small copper mine in Allotment A 15 a, Parish of Knowsley East. This is the type locality for selwynite, a fuchsite-corundum rock originally described as a mineral species. The surrounding rocks are schistose 'diabase'. LOCALITY 45. A further enclave of Upper Ordovician sediments outcropping in McIvor Creek just north of Heathcote contains Dicellograptus, diplograptids, Climacograptus and Lingulella. LOCALITY 46. A series of bodies of fine-grained granodiorite intrude the Heathcote Greenstones about the township of Heathcote. These are surrounded in part by aureoles of calcareo-siliceous rocks which have been interpreted as aureoles of contact metamorphism. Masses of cleaved and sheared 'diabase' have been caught up in the se intrusions showing that intrusion post-dated some of the shearing but the precise dating of these bodies remains equivocal. It is still open to debate whether the intrusions were initially sodic, whether there was in fact introduction of carbonate from the intrusions into the surrounding aureoles, whether the carbonates are to be attributed entirely to the original composition of the diabases, or whether the sodic nature of the granite is to be connected with the albitization of the Heathcote Greenstones. Magnesite veins within the 'granite' and the sheared 'diabases' have been exploited c omme rc iall y. LOCALITY 47. The Heathcote Fault is here expressed as a quartz blow between the Heathcote Greenstones and Ordovician (Lancefieldian) sandstones and slates to the W. LOCALITY 48. Richly fossiliferous sandstones in Allotment B27, parish of Goldie. This marker horizon has been used to separate the Springfield Beds from the Chintin Beds. LOCALITY 49. A stratigraphic succe ssion at Darraweit Guim include s the Ordovician-Silurian boundary, in an area where Ordovician sediments containing Bolindian graptolites recur in anticlinal zones flanked bylowersilurian (Keilorian) sandstones and mudstones. Shelly faunas,including trilobites, hyolithids and small ctenodontid bivalves occur,in outcrops beneath and immediately W of the bridge over Deep Creek in the village of Darraweit Guim. Their significance, if any, in determining the age of these beds immediately above the Bolindian horizon has yet to be dete rmine d. IN TRANSIT. The route back to Melbourne follows up a tributary of Deep Creek to the old Sydney Road. The sequence well exposed in the creek bed consists of LowerSilurian siltstones and silty sandstones notoriously poor in fossil remains. It is uncertain whether Middle Silurian horizons are represented in this sequence.
96 82 SELECTED REFERENCES The references not given below, and the extensive earlier literature, are listed in Keble and Benson (1939),and Thomas (1960). Harris, W.J. and Thomas, D.E., A revised classification and correlation of the Ordovician graptolite beds of Victoria. Min. Geo!. Jour. Vic. 1(3) : Keble, R.A., and Benson, W. N., Graptolites of Australia. Bibliography and history of research. Mem. Nat. Mus. Vic.,.!..! : Singleton, O. P., The geology and petrology of the Tooborac district, Victoria..f.!..2. ROY.Soc.Vic. 61: Talent, J.A., 1965a. The stratigraphic and diastrophic evolution of central and eastern Victoria in middle Palaeozoic times. Proc.Roy.Soc.Vic. 79: Talent, J. A., 1965b. The Silurian and early Devonian faunas of the Heathcote district, Victoria. Geo!.Surv.Vic.Mem Thomas, D. E., Some notes on the Silurian rocks of the Heathcote area. Min. Geo!. Jour. Vic. 1(1): Thomas, D.E., The structure of Victoria with respect to the Lower Palaeozoic rocks. Min.Geol.Jour.Vic. 1(4): Thomas, D.E., The Bendigo goldfield in Edwards, A.B., ed., Geology of Australian ore deposits,lst Ed., Thomas, D. E., The zonal distribution of Australian graptolite s. Jour. Proc. Roy. Soc. N. S. W. 94 : Thomas, D.E. and Singleton, O.P., The Cambrian stratigraphy of Victoria. EI Sistema cambrico, su Paleogeografia y el Problema de su Base, XX Int. Geol. Congr. (Mexico) 2 : G, b. Olde. Pliocene. c. lava. d. Lowe. Newe. l'lioceue. The V~ham deep lead, Buninyong. F.M.K~U6e - P~og. Rep. Geol. S~V. Vic., it I
97 CHAPTER THE CASTLEMAINE-CHEWTON GOLDFIELD by F. C. Beavis and J. McAndrew INTRODUCTION. When the discovery of the Castlemaine goldfield, in July, 1851, became public in late October or early November of that year, the phenomenal richness of the alluvial surface led to a rush even from the rich Ballarat field discovered in August. Originally known as the Mt.Alexander diggings, covering some IS sq.miles, 93,000 oz. of gold was sent to Melbourne in the last seven weeks of 1851, and the first ten years production has been estimated as 3,500,000 oz. Quartz reefs' gave remarkable yields from outcrop, over 250 oz. to the ton at Wattle Gully, and were rich at shallow depths, with large parcels of ore returning up to 12 oz. of gold per ton. The economic importance stimulated early detailed geological mapping, and the Geological Survey of Victoria published by 1864 splendid, detailed Geological Quarter Sheets of the field. The pioneer palaeontology of T. S. Hall (1894) followed by W. J. Harris (19l6) elucidated the rich graptolitic sequence of the field. The Castlemainian (Hall, 1899) and Chewtonian and Yapeenian (Harris and Thomas, 1938) Series of the Lower Ordovician are named after three towns within a five mile radius on the goldfield. More recently D. E. Thomas has deciphered the detailed geological structure of the Ordovician at Chewton by meticulous mapping utilizing individual graptolite bands as marker horizons. GENERAL GEOLOG Y. The Ordovician bedrock is a monotonous repetition of slates, siltstones, and quartz sandstones, silty sandstones or sandy siltstones generally termed sandstones or, more recently, greywackes. These are closely and sharply folded along meridional axes. Individual beds are characteristically a few inches to several feet thick, with both simple and oscillatory gradation, the latter possibly more frequent. The slates have abundant graptolites, a few phyllocarids, and rare pelecypods. To the north the sediments are intruded by the Harcourt Granodiorite with a narrow metamorphic aureole, the contact being 2 miles north-east of Chewton( Fig. 2). With the exception of Mt. Alexander, the granodiorite forms low cleared country bordered by a timbered ridge of the aureole. The Ordovician is undulating to hilly with poor soils and frequently uncleared stringybark or ironbark forest. ORDOVICIAN. Mac roscopic Structure. In central Victoria the Ordovician forms major N-S synclinoria and anticlinoria (Thomas, 1939) (see Chapter 9. and its Fig. 1). Between Chewton and Castlemaine. 21- miles to the west, is the hinge of the Blackwood-Trentham Anticlinorium. and shortly east of Chewton is the subsidiary Expedition Pass Synclinorium. In this area these plunge gently north, with the latter reversing its plunge northwards near the granodiorite contact. The sediments in this district are mainly Chewtonian and Castlemainian (Didymograptus protobifida and Isograptus caduceus vars. as zone fossils). with younger
98 84 Yapeenian beds, containing Onco. graptus upsilon and Cardiograptus morsus, in the hinge zone of the Expedition Pass Synclinorium. Regional reversals of plunge re sult in the broad dome and basin structures, and the common passing of synclinorium into anticlinorium and vice versa along the hinge line, producing an overall en echelon pattern of folds. The hinge line s strike a few degrees west of north, and the limbs dip between 70 0 and 90 0 The smaller folds are tight and sharp, with axial plane separation of about 100 yards, although locally as little as 3 to 6 yards. In the Chewton Castlemaine area the highly developed slaty cleavage. an axial plane foliation, has a steep dip of about 80 0 W and the folds are asymmetrical (Fig. I). Westward from Castlemaine the cleavage becomes vertical, then east dipping down to 60 0 to 65 0 at Maldon. This regional pattern reflects the fanned nature of the :pj.acro scopic folds. Fig.l. Section through Wattle Gully showing relation of reefs to major structures (after Thomas,1953). Mesoscopic Structure. The excellent exposures near Chewton show the detailed mesoscopic structural elements of the Ordovician sediments. 1. Folds. The mesoscopic folds vary with lithology but have an overall similar style. Folds in the slates are almost ideally similar with sharp, thick hinge zones and marked thinning of the steeply dipping limbs. Axial plane slatey cleavage is highly developed. Folds in the sandstones tend to be more open with quite rounded hinge zones; there is some thickening of the hinges and thinning of the limbs, but this is considerably less than in the slates. Laminated, oscillatory graded siltstones, which often occur between the slates and sandstones. fold in a comparable manner but are often also crumpled. Thick slate s confined between thick sandstone s frequently have disharmonic folding. Axial surfaces of the mesoscopic folds are generally slightly curved, and the hinge lines gently plunging but also curved. Reversal of plunge occurs frequently so folds die out quite rapidly. The mesoscopic folds, like the macroscopic, are nonplane non-cylindrical. The asymmetry varies considerably. The Expedition Pass syncline at Expedition Pass, 2 miles north of Chewton, is markedly asymmetric, while in Forest Creek at Chewton the folds are only slightly asymmetric. With rare exception, the folds have triclinic symmetry.
99 85 2. Cleavages. Lithological control of cleavage style is clearly seen in the Chewton area. Three distinct types of cleavage occur: slatey cleavage in slates; strain slip cleavage in laminated siltstones; and fissuring in sandstones. It is considered that all three types developed essentially contemporaneously in response to the same stresses during the folding of the rocks. All are, at least statistically, axial plane cleavages. The slatey cleavage is totally penetrative. Strain slip cleavage and fissuring tend to be restricted to the hinge zones of the folds, and occur in discrete zones with evidence of flow within the cleavage domain. Accompanying both, particularly strain slip cleavage, is small scale folding or puckering of the bedding. The cleavages curve markedly across graded beds, with sharp refraction of cleavages at bedding planes. The openness of some cleavages is due to weathering and to tensile stress from erosional unloading. The cleavages are a I'+++] L.+J em ~ Harcourt Granodiorite Metamorphosed Ordovician sediments (hornfels etc.) o Ordovician sediments + CD Excursion localities t Major fold hinges (appro x J Recent alluvium (auriferous) not shown. SCALE /2 ~.5: o, 1112 MILES = 3 KM i I I I -+ I I ~~ r~~~' +, I, Fig. 2. Geological map of Chewton-Castlemaine area, showing localities of itinerary.
100 86 guide to the mechanism of folding deformation. Even in the more compatent beds, particularly in the hinge zones of the folds, flow in cleavage domains played an important part in the folding. One notable feature is the variation in attitude of the cleavages. Throughout the slates, the slatey cleavage is parallel to the axial surface of the fold. Strain slip cleavage and fissuring, in contrast, have a radial pattern, with true axial surface geometry only on the hinge itself. Overall. however. these cleavages are statistically parallel to the slatey cleavage and the axial surface of the fold., 3. Lineations. Lineations parallel to the fold axes are found in all three rock types, the style tending to be controlled by lithology. In the slates, lineation consists of fine microcrenulations in the bedding, due to its intersection with the slatey cleavage. Colour bands on the slatey cleavage, representing the trace of the bedding laminations on the cleavage surface, are also fold axis lineations. In the laminated siltstones, the hinges of the small folds are linear structures parallel to the axis of the larger fold, and in the sandstones. cuspate structures associated with the fissuring are to be regarded as rudimentary mullions. Other linear structures present are drag folds in some thinner sandstone beds, and lozenge structure resulting from conjugate cleavages in siltstones and finer sandstones. GRANODIORITE CONTACT. The metamorphic aureole developed in the Ordovician sediments adjac.ent to the Harcourt Granodiorite is exposed between Expedition Pass, 2 miles north of Chewton, and Faraday. Here the metamorphism is comparable with that at Big Hill on the northern edge of the batholith, which has been studied in detail (Beavis, 1962). About % mile from the contact the slates show faint spotting. Near Expedition Pass crystals of andalusite have developed, while at the contact itself are biotite-cordierite hornfels. In this area the intrusion has little structural effect. but elsewhere crenulation cleavage has been superposed parallel to the contact. On the eastern margin there is. additionally. a distinct curvature of fold hinges parallel to the contact, due to forcible intrusion of the batholith. GOLD DEPOSITS. In the central Victorian goldfields auriferous quartz reefs are cloliely associated with structures in the Ordovician sediments (McAndrew, 1965). A major source of lode gold production from these goldfields has been quartz reefs and associated 8pUr$ along reverse movement strike faults dipping at moderate angles to the west. Lodes along these occur largely where the faults cut acr08s the easterly dipping sediments in the eastern limbs of the anticlines. The Wattle Gully lodes at Chewton. for many years the only major quartz reef to be mined in the central Victorian goldfields, are of this type. Approximately half of the gold production from the many mines in the Chewton area has been from spurs, irregular quartz masses and veins which occur in all attitudes, and may be mutally cross-cutting to form a stockwork. and may extend out from fault reefs as well as occurring separately, and are variably auriferous (Thomas, 1953). Gold-quartz saddle reefs were worked in some mines on the field, and o::casional reefs along faults cutting across the strike of the sediments (cross-courses). Wattle Gully Mine. The Wattle Gully lode was discovered in 1935 from exploration for a downwards extension of the Phillips R~ef (Fig. I}, worked about 1860 to The operations have paid approximately $1,500,000 in dividends for a subscribed capital of $77,000. Production from 1935 to 30th June, 1966 totals 324,272 oz. of bullion from 929,000 tons of ore. The gold is about 950 fine. Until recently production was approximately 2,900 tons per 4 week period, yielding 6.7 dwt per ton. The mine was kept in successful operation by a technical rehabilitation programme from 1955 to 1960, including construction of the new treatment plant. coupled with a policy of vigorous underground exploration. This has been described by Clarke and Thomson (1965).
101 87 ~ o M ~ o N ~ o M o 6 Level_ Level_ 8 Level- / / I I 9 Level_ R L Level_ 11 Level R L Level_ Wattle Gully 650 DYke and Fault ']TZ:-:::;:::~~ SandstoY'e g:::::::: Gully Slates ~ Quartz reefs Fig. 3 (above). Cross section of Wattle Gully lodes at 350 N (Clarke and Thompson, 1965). Fig. 4 (below). Plan of 12 Level, Wattle Gully Mine (1086 ft. below surface).
102 88 The geological setting of the lodes is shown by the cross section, Fig.l. The reefs occur along a system of reverse faults which dip at moderate angles to the west across the steep easterly dipping to vertical sediments on the eastern limb of the anticline. In depth the faults refract across the Wattle Gully anticline and become bedded in the west dipping sediments. Recent mine development has shown that the fault and reef system is continuous with Phillips Fault and reef. Longitudinally the auriferous reef pitches flatly north. Persistent northwards exploration in the mine has disclosed two flatter profitable reefs which successively diverge eastwards into the footwall off the upper reef being followed. These occur along more flatly dipping faults and are distinguished in Fig. 3. Only the uppermost reef is present at the southern end of the mine. The lowest reef, present only in the north of the mine, is diagrammatically projected onto the cross section to illustrate its position relative to the other reefs. where it has diverged away from the fold axis. The quartz is up to 100 ft. wide along the junctions of the reefs in the sandstone. Spurry quartz, runs into the wallrock from the main reef, and the veins split on entering the Wattle Gully slate from the sandstone. The quartz reef varies greatly in grade. Gold rich shoots form isolated bodies within it which begin and end abruptly. Higher grade ore occurs especially where the reef is in the Wattle Gully slates above their lower boundary with the sandstone, and for up to 50 ft. into the sandstone, as well as where intercalated slate and sandstone form the footwall. Much of the gold is relatively coarse, over 40% is coarser than 1/12 in. aperture mesh, and 5% is coarser that ~ in. aperture. ITINERARY IN TRANSIT - Melbourne to Chewton (72 m.) Newer Basalt from Melbourne to Black Forest (36 m.)passing eroded volcanoes especially at 26 m.,and Mt.Gisborne at 31 m. (see Chapter 11 - Macedon). Black Forest - messmate on Ordovician. Upper Devonian volcanics of Mt.Macedon to E. Woodend (43 m.) to Taradille (64 m.) on Newer Bas<.lt. Upper Devonian Cobaw composite pluton east; of Kyneton _ partially gralillied dumps of gravel from deep leads beneath basalt; in vicinl.ty of Malmsbu~y. I Elphinstone (67 m.) - Ordovician. view to Mt.A.lel!;ander (Harcourt Granodillrite I with TV tower. LOCALITY 1 - Chewton Type locality of Ch,ewtonian Zone Ch 2, Didvmosram;us erotob!fidus, in black slate of mine dump immediately NW of railway bridge across Wattle Gully Rd., Chewton. LOCALITY 2 - Fryer!3town. Graptolitic dates of Chewtonian Zone ChI, west side of road cutting, Chewton-Fryerstown Road, 2t miles liouth of Chewton railway bridge. Close folds in slate, with cillavalle, linllations, and strongly developed!. joints. LOCALITY 4 - Railway cuttinis, Chllwton. Folds with change s of plunge.
103 89 LOCALITY 5 - Lyttleton St., Castlemaine. Anticlinal fold in cliff on N side of road. LOCALITY 6 - Urquhart St., Castlemaine. Basal deformation of sandstones resting on shales, west edge of street (Hills and Thomas, 1954, Plate 1, Fig. 1). LOCALITY 7 - Expedition Pass. Expedition Pass syncline in andalusite hornfels, contact of Harcourt Granodiorite. REFERENCES Beavis, F.C., Contact metamorphism at Big Hill, Bendigo, Victoria. Proc. Roy. Soc. Vic., 75: Clarke, P.E. and Thompson, I.R., Operating experience at Wattle Gully in relation to the central Victorian gold mining area. 8th Corom. Min. Met. Congr., Preprint 6. Hall, T. S., Geology of Castlemaine. Proc. Roy. Soc. Vic., 7: Hall, T.S., The graptolite-bearing rocks of Victoria, Australia. Geol.Mag., 6: Harris, W. J., The palaeontological sequence of the Lower Ordovician rocks of the Castlemaine district. Proc. Roy. Soc. Vic., 29: Harris, W.J. and Thomas, D.E., A revised classification and correlation of the Ordovician graptolite beds of Victoria. Min. Geol. Jour. l{ 3): Hills, E.S. and Thomas, D.E., Fissuring in sandstones. Econ.Geol., 40: Hills, E. S. and Thomas, D. E., Turbidity currents and the graptolitic facies in Victoria. Jour. Geol. Soc. Aust., 1: McAndrew, J., Gold deposits of Victoria, in Geology of Australian Ore Deposits, 2nd ed., Ed. J. McAndrew, {8th Comm.Min. Met. Congr. Melbourne} Thomas, D.E., The structure of Victoria with respect to the Lower Palaeozoic rocks. Min.Geol.Jour. 1(4): Thomas, D.E., The Cast1emaine - Chewton - Fryerstown Goldfield, in Geology of Australian Ore Deposits, 1st ed., Ed. A. B. Edwards, {5th Empire Min. Met. Congr., Melbourne}.
104 90 CHAPTER 11 GEOLOGY AND PETROLOGY OF THE MACEDON DISTRICT by O. P. Singleton INTRODUCTION. This region is of particular interest because of its extensive Newer Volcanic olivine?asalt - trachyte suite and features of the associated volcanoes (Fig. 1 to 3). PHYSIOGRAPHY. The Mt. Macedon district. some 40 miles north-west of Melbourne. straddles the main divide in the Western Highlands of Victoria. Monadnocks of the more resistant rocks project above the uparched early Tertiary erosion surface cut in Lower Palaeozoic sediments. Mt. Macedon ( ft.), itself a strongly dissected remnant of an older erosion surface, is of Upper Devonian hypersthene dacite. with lower buttresses of granodiorite and Kerrie Conglomerate on the south-east and east. To the north the Cobaw Ranges (2, 500 ft.) delineate the metamorphic aureole and marginal portion of the Cobaw batholith, and to the north-east the Mt. William Range culminating in Mt. William ( ft.) is a strike ridge of Cambrian greenstones forming part of the Heathcote axis. The early Tertiary erosion surface was arched late in Tertiary time along an east-west axis. attaining a maximum elevation of Z,900 ft. in a domal structure centred some 20 mile s west of Mt. Macedon. It lies at Z ft. in the Black Forest at the western foot of Mt. Macedon and at ft. on the north. The southerly slope of this surface is interrupted south of Gisborne by pre-newer Volcanic faulting along the east-west Gisborne Fault. The strongly dissected southerly facing scarp dies out eastwards and marks the northern edge of the basalt-covered Werribee Plains block on which the erosion surface resumes its southerly tilt. Uplift of the Gisborne fault block impeded drainage in the headwaters of Jackson's Creek and probably led to the accumulation of thick pre -volcanic gravels we st of Gisborne. Arching of the eariy Tertiary erosion surface antedated the Newer Volcanics and except near the Gisborne Fault it was only mildly dissected prior to their extrusion. The pre-volcanic streams, indicated by sub-basaltic deep lead gravels. had similar gradients to the present ones, both having attained grade over much of their course. The major effect of the lava flows was to divert streams laterally. with only minor interruptions to drainage directions. Claims for reversal of pre-volcanic drainage cannot be sustained. 'Damming' of the upper tract of Deep Creek has caused alluviation near Lancefield where one deposit has yielded bones of Diprotodon. Post-volcanic stream erosion has been largely confined to down-cutting to produce steep-sided valleys on xnajor streaxns. such as that of Jackson's Creek near Sunbury. The lavas were extruded from a large number of vents. whose form can be correlated with the associated rock type. From their state of preservation and from radiometric dating of similar flows near Melbourne, it is probable that volcanoes in the Mt. Macedon district are mainly Pliocene perhaps ranging into the early Pleistocene. The earlier lavas and most volcanoes are modified by erosion but the later basalts show little surface modification except for the development of soils. LOWER PALAEOZOIC BEDROCK. The area lies to the west of the Heathcote Axis whose western flank shows a conformable sequence from Cambrian to Ordovician (see Chapter 9). Bedrock consists of tightly folded greywackes and slates ranging in age from Lower to Upper Ordovician. The Upper Ordovician west of the Heathcote Axis is distinctive in the presence of neritic sandstones and grits with fragmentary shelly fossils (Riddell Grits). rather than the usual bathyal deposition. North of Mt. Macedon the structure is synclinorial with Darriwilian beds in the centre. whereas to the south, the Djerriwarrh Fault complicates the picture and marks the western limit of occurrence of Upper Ordovician in the State.
105 91 ~ Hypers!hrne-TrK'lIIdesde ~ D. fegley's Trachyanclrs!. Qlicoclase-bas.l Umburgd. r-:-:-:-: ~ mvint-ba>ilt :::::::::: Liltlt Seollanm.. ~ IddlOgSltt-wlt ~ funston's Quarry Flow r.. llddin'sit.-bm~ :.:..:,~ Junors Quarry Flow Iddin&S!I.-,ug,te-b.sall McGtorg.s H,II flow c C.v. ONLY OEflNln OUTCROPS ARE SHOWN W Waterl,1I Fig. 1. Geological map of the Gisborne district, distribution of the New~r Volcanic _rocks (Edwards showing the and Crawford, 1940).
106 92 UPPER DEVONIAN. 1. Kerrie Conglomerate. The eastern end of the Macedon range is occupied by massive unfossiliferous quartzose conglomerates and sandstones resting unconformably upon the Ordovician and in part derived from the Riddell Grits (Thomas. 1932). The basal beds contain boulders up to two feet across and dips are generally westward towards the hypersthene dacite. Unfortunately the Barringo Granodiorite which intrudes both obscures any relationship to the dacite. Although of unknown age. the Kerrie Conglomerate is usually assigned to the Upper Devonian. 2. Mt. Macedon Hypersthene Dacite. The hypersthene dacite forming Mt. Macedon is a body of uniform composition at least ft. thick. Although no evidence of a bounding fault or ring dyke has been found. it probably represents the filling of a cauldron subsidence. It consists of phenocrysts of zoned plagioclase. hypersthene. ilmenite. and occasional biotite in a microgranular groundmass of quartz. alkali felspar, and occasional biotite. Deuteric alteration occurs locally near Hesket. Where metamorphosed by the consanguineous Barringo Granodiorite. biotite aggregates have developed at the expense of hypersthene and ilmenite, and similar but less obvious alteration is present in dacite inclusions in the Camel's Hump soda trachyte. 3. Barringo Granodiorite. This is typical of the granodiorites associated with the central Victorian Upper Devonian rhyodacite suite. Besides the area shown on the map a small outcrop occurs within the dacite at Clyde SchooL Analyses of both are given in Table 1. NEWER VOLCANICS. The widespread Newer Volcanics occur as valley flows and small lava fields in the Western Highlands and nearer Melbourne spread out as an unconfined lava field on the Werribee plains. The Mt. Macedon district lies in the eastern half of an oval area 80 miles E-W by 50 miles N-S centred on Trentham. which contains a remarkable concentration of over 200 vents. This concentration coincides with the late Tertiary domal uplift referred to previously. although volcanicity post-dates the uplift. While olivine labradorite basalts greatly predominate. diffe rentiates ranging from soda trachyte to limburgite occur. particularly in the Mt. Macedon and Trentham districts. that i8 along the axis o.f uplift. Most differentiates fit closely into a normal olivine basalt-trachyte suite. although a few types. notably the hypersthene trachyandesites and the alkali limburgite, 'woodendite'. are anomalous in composition. The petrology has been described by Skeats and Summers (1912). Edwards (1938). and Edwards and Crawford (1940). while geochemical aspects are the subject of an unpublished thesis by Bahat (1966). Edwards recognised a large number of gradational petrological types: his nomenclature is followed in general. although this does not always agree with current practice. Representative analyses are given in Table 1. Volcanoes. There are over 40 volcanic hills in the Mt. Macedon-Gisborne' area. most of them small (from twenty to several hundred feet in height). short-lived. and associated with only one rock type. Their form varies with the viscosity of the lava, which correlates with the silica and alkali contents. The most siliceous lavas. the soda trachytes or 'solvsbergites' (with 650/0 to 67% SiOZ)' were extruded in a highly viscous state. building the steep-sided mamelons of the Camel's Hump. Hanging Rock. and Brock's Monument. These are somewhat eroded, helped by strong vertical jointing which at Hanging Rock in particular has been etched out leaving large pinnacles on the summit. The anorthoclase trachytes (59% to 62% SiOZ) varied in viscosity. McAlister's Rock. the Jim Jim. and Mt. Eliza are lava domes with steep hummocky sides whereas other trachytes near Newham and Hesket have gentler slopes. The hypersthene trachyandesites (57% to 61% SiOZ) forming the main lava dome on Mt. Gisborne behaved similarly. The basalts were generally very fluid but gently sloping basalt shields. s'uch as Beattie Hill near Mt. Gisborne. are uncommon. Fig. 2 (opposite). Geological map of the Macedon district.
107 HOLOCI::!JI:: c=3 Al luvi um H A N G E, V'. v ' -;' ' ' y cj!)'., ~ -Q ',- PL IOCl:.t'lll::. '1'0 P LL I S1'OCLN' 0 hlkali lim1..ourgite //// (woodendite) ~ 0 [Q [2J 0 ~ LiI;lbu rg i te LilllLu rgl.tl.c oasalt Labrador i te basalt 0 ~ Anoes iue oasalt v.. ~ v Ol ivine oligoclase basalt ~ Oliljoclase v v, tracnybasalt (maceaonite) V V.. r=j Anorthoclase olivine trachyte. v v.. Anortnoclase EEE t racny t e v v.. v v Soda E~ trachyte (solver sberg i t e) Hyper sthene trachyanues i te,.. v v I ~!O~Er.EETTA,v v, J l~,. v V TeRTIARY Gravels UP Pl:.R ljl:.vot~ lln Granodiorite V v I IV '-- V ' V v )V I ' V V.... HAr.~ET HILL V V .. v v v v ORDOV I ClhN hype r s t hene aacit~ Kerrie Con o:;,.lololl.: rate V.. I, /,' ~l~ '1' volcanic v ~nt V V V V V V V MILLS V.. V (J / Fault koad N t v V v v v ' ' A REGIONAL GU IDE TO
108 93 Most of the basaltic volcanoes are cones of pyroclastics and scoriaceous lava built after the main effusive phase, although some such as Magnet Hill are largely lava. Intercalated flows are common and dykes occur occasionally, as at Mt. Kororoit. Craters have been removed by erosion. The volcanoes between Sunbury and Gisborne show a characteristic erosion profile (Fig. 3) with flat top and gentle slope on one side both capped by lava, representing the central plug and final flow from a breached crater. Mt. Gisborne (2, los ft.) rising SOO ft. above its base, illustrate s a small group of longe r lived volcanoes composed of a variety of rock types. It shows three eruption points and has the most co'mplex extrusive history of any Victorian volcano. Order of Extrusion. Taken over all,the order of extrusion was from acid to basicbut,in detail,reversals in this trend occurred. The main flood of olivine basalts followed the extrusion of most of the diffe rentiate s. At Mt. Gisborne (Fig. 2) the first phase included four confined flows of unknown mutual relationships - andesine basalt (NW), oligoclase basalt (SW), limburgite (S), and limburgitic basalt (S). During a succeeding quiescent period impure diatomaceous earth accumulated in small lakes ponded by some of these flows. Lavas of the next phase, the Gisborne hyperstheneolivine basalt and Funston's Quarry iddingsite basalt, spread much more widely. These were followed by hypersthene trachyandesite flows which built the main lava dome. In the final phase iddingsite basalts, the McGeorge's Hill and Junor's Quarry flows, were extruded from two vents on and beside this lava dome. Petrology. 1. Hypersthene Trachyandesite - Analyses 4, S. Three flows of hypersthene-bearing trachyandesite originated from Mt. Gisborne, two occurring on the mountain and one in an inlier at the Giant's,Grave on Jackson's Creek. The grey trachyandesite forming the bulk of Mt. Gisborne contains phenocrysts of sanidine, occasional anorthoclase, and labradorite (An60), diopsidic augite, hypersthene (En70), and occasional olivine set in a dark glassy groundmas s with hype rsthene laths rimmed by augite and from which microlites and laths of oligoclase(an2s) and incipient augite have crystallized. The phenocrysts, except augite, show resorption, and rounded xenocrysts of quartz are common. The underlying de Fegley's trachyandesite and similar Giant's Grave flow are dense glassy rocks differing only in the absence of olivine and groundmass hypersthene. In these rocks phenocrysts of feldspar, principally labradorite, hypersthene, and sometimes augite, tend to form clots up to 3 cm. ac ros s, a preliminary stage in the formation of xenoliths of noritic composition which are common in the two first-named flows. These noritic xenoliths consist of hypersthene intergrown with labradorite, sometimes accompanied by augite. Finegrained xenoliths in the grey trachyandesite with the composition of hypersthene basalt show occasional hypersthene and iddingsitized olivine phenocrysts in a finely vesicular intergrowth of prismatic colourless hypersthene rimmed by augite and labradorite (An6S)' 2. Soda Trachyte (IISolvsbergite ') - Analyse s 6, 7. The soda trachytes of the Camel's Hump, Hanging Rock. and Brock's Monument diverge from the differentiation trend of the suite in being lower in potash and alumina than the less siliceous anorthoclase trachytes. Soda is high (6% to 7%) leading to the crystallization of soda amphiboles in the groundinass. The fresh rocks are greenish due to their aegulne content. Phenocrysts of aggregated anorthoclase microperthite up to 3 mm. long. later soda sanidine about I mm. long, and occasional aegirine augite are set in a groundmas s of soda sanidine. aegirine, soda amphibole. iron ore, and occasional shreds of biotite as the final crystallization product. The amphibole is riebeckite at the Camel's Hump, but arfvedsonite and cossyrite at the other two localities. 3.,Anorthoclase Trachyte - Analyses 8 to 1l. In this group soda and potash are present in ne;,rly equal amount. Phenocrysts of anorthoclase up to 1 mm. long in aggregates subsequently rimmed by orthoclase, with soda sanidine and
109 Si0 2 A Ti0 2 Fe FeO MgO CaO Na 2 0 K 2 0 H 2 O+ H 2 O- CO 2 P2 05 MnO Etc. Total nil nil tr. tr loq.75 :1, tr _~~.~TJ Hypersthene Dacite Barringo Granodiorite Older Basalt Grey Hypersthene Trachyandesite Hypersthene Trachyandesite (De Fegley's flow) Soda Trachyte Soda Trachyte Anorthoclase Trachyte Anorthoclase Trachyte Anorthoclase Olivine Trachyte Olivine Anorthoclase Trachyte Oligoclase Trachybasalt Oligoclase Trachybasalt nil lj)o~ tr. nil tr. tr tr L-99 6l Willimigongong Ck., U. Macedon Hesket Tullamarine Mt. Gisborne Mt. Gisborne Hanging Rock Camel's Hump Camel's Hump Turritable Falls, U.Macedon Sugarloaf, Newham Cobaw Melbourne Hill, Lancefield Spring Mound, Rochford TABLE I nil tr. nil - I _ ~~ Analyst: F.L. Stillwell, 1912 A.B. Edwards, 1940 A.B. Edwards, 1940 A.G. Hall, 1907 A.G. Hall, 1907 D. Bahat, 1966 A.G. Hall, 1907 A.G. Hall, 1912 A.G. Hall, 1912 A.B. Edwards, 1938 A.G. Hall, 1912 ~ ~ ' ~.
110 ~ TABLE I cont'd Si j A : Ti I Fe i FeO ! MgO CaO i Na i I K H 2 O H 2 O CO nil nil nil 0.05 nil nil tr. tr. tr. P MnO tr Etc Total Olivine Oligoclase Basalt Murray's spur, S.W. of Mt. Gisborne A.B. Edwards, Olivine Oligoclase Basalt Deep Ck., E. of Melbourne Hill A.B. Edwards, Andesine Basalt N.W. of Mt. Gisborne A.B. Edwards, Porphyritic Olivine Andesine Basalt Rocky Ra., W. of Romsey A.B. Edwards, Hypersthene Olivine Labradorite S. of Mt. Gisborne A.B. Edwards, 1940 Basalt (Gisborne type) 19. Olivine Labradorite Basalt NNE of The Jim Jim, Hesket A.G. Hall, Olivine Labradorite Basalt (Trentham type) S. of Rochford A.B. Edwards, Olivine Labradorite Basalt (Church Hill flow) Gisborne A.B. Edwards, Iddingsite Labradorite Basalt (Junor's Quarry Flow) Mt. Gisborne A.B. Edwards, Iddingsite Labradorite Basalt Duck Holes Ck., S. W. of Romsey A.B. Edwards, Limburgitic Basalt Toolern Ck., S. of Mt. Gisborne A.B. Edwards, Limburgite King's Quarry, Hesket, U. portion A.G. Hall, Limburgite King's Quarry, Hesket, L. portion A.G. Hall, D 27. Alkali Basalt ( 'Woodendi te' ) Old Racecourse Hill, woodend A;G. Hall,
111 96 occasional oligoclase and aegirine augite are set in a groundmass of alkali feldspar probably soda sanidine. aegirine. iron ore. apatite. and sometimes glass. Unstable diopsidic pyroxene is occasionally pre sent. As the trachyte s become more basic anorthoclase decreases in amount and is increasingly resorbed. aegirine is replaced by aegirine augite at which stage olivine appears. and lastly diopsidic augite enters as the phenocryst pyroxene. Such rocks. represented at Sugarloaf, Newham and Cobaw, are variable and grade into the trachybasalt group. It may be noted that the Trentham group of trachytes are somewhat less siliceous but more sodic. and one rock called a trachyphonolite by Edwards has developed sodalite and rare nepheline. 4. Oligoclase Trachybasalt (IIMacedonite ll ) - Analyses These mugearitic rocks are intermediate in chemical and mineralogical composition between the trachytes and olivine basalts. They are fine-grained. with occasional microphenocrysts of altered olivine. rare diopsidic pyroxene. and resorbed anorthoclase set in a groundmass of oligoclase (An2S).? orthoclase, iron ore, coarse and fine apatite, and interstitial biotite and hornblende. At Melbourne Hill the olivine is iddingsitized but at Rochford alte ration has been to chlorite and se rpentine. S. Olivine-Oligoclase Basalt - Analyses 14, IS. More widespread than the preceding, these oligoclase basalts differ in the presence of groundmass olivine. either fresh or iddingsitized. Corroded phenocrysts of olivine and augite, and in some rocks anorthoclase, occur in a groundmass of olivine, oligoclase (An2S-30)' augite, iron-ore, apatite and occasionally biotite, with or without glas s. 6. Ande sine Basalt (IIBallan Type II ), - Analyse s 16, 17. The typical BalIan type is an iddingsite-augite-andesine basalt which is higher in alumina and lower in magnesia and grades into the Malmsbury type of labradorite basalt. Such rocks occur frequently as the final extrusions fro:m volcanic hills, e. g., Rocky Range, The Ji:m Ji:m. Iddingsitized olivine, diopsidic pyroxene, and plagioclase (An SO ) which is very conspicuous in so:me flows, e. g. Rocky Range, are set in a ground:mass of the sa:me :minerals but with less calcic plagioclase (An 4S ). The Mt. Gisborne andesine basalt however differs in the absence of olivine and approaches closer to the oligoclase basalts. Phenocrysts of plagioclase (AnSO) and occasional pyroxene occur in a base of andesine (An30)' pyroxene, iron ore, and abundant black glass, with secondary calcite. 7. Labradorite Basalt - Analyses Edwards distinguished between rocks containing olivine which may be serpentinized but never iddingsitized, and those in which olivine has been partially or completely altered to iddingsite. The olivine basalts are usually older than the iddingsite basalts. (i) Olivine-Labradorite Basalt (IITrentham Type'). Phenocrysts of corroded olivine (FoSS)' and diopsidic pyroxene occur in a groundmass of labradorite (AnSS)' pyroxene, iron ore, and green feldspathic glass. Olivine is never present in the ground:mass. A distinctive variety, the Gisborne basalt, shows affinities with the hypersthene trachyandesites. Large phenocrysts of labradorite (An60) and occasional anorthoclase, both resorbed and rimmed with labradorite (Anso), less augite, hypersthene (ca. En70) rimmed with augite, and corroded olivine occur in a groundmass of labradorite (AnSO)' augite, iron ore, apatite. and a varying amount of green glass. Xenocrysts of quartz fringed with augite are rarely present. In a related rock from Campbell'[J Creek, Gisborne, the ground:mass feldspar is oligoclase (An2S). (ii) Iddingsite-Labradorite Basalt (IIMal:msbury and Footscray Types ll ). The widespread flows of the lava plains ar~, largely iddingsite-iabradorite basalts. Phenocrysts may be iddingsitized olivine alone. olivine and diopside augite. or olivine + augite + labradorite (An60). Olivine. normally iddingsitized. occurs in the groundmass. The degree of iddingsitization varies. Variants include the Malmsbury basalt with a doleritic texture and little or no glass and the Footscray basalt with slightly titaniferous augite and colourless to brown glass.
112 97 ' Fig. 3. Origin of the flat-topped volcanic hills in the Gisborne district. A. Breached volcanic cone. B. After erosion. (Edwards and Crawford, 1940). 8. Limburgitic Basalt - Analysis 24. Certain flows are similar to the limburgites but differ in containing a small but persistent amount of plagioclase. In the flow from Mt. Gisborne laths or microlites of composition ca. An have crystallized from the brown glass. 9. Limburgite - Analyses 25, 26. Limburgites occur generally as small flows and show a distinctive nodular weathering. Small phenocrysts of olivine, unaltered when glass is absent, and monoclinic pyroxene sometimes rimmed by titanaugite are set in a base of pyroxene, iron ore, and a varying amount of glas s. Felspar. generally soda plagioclase, and analcite are present in some rocks. Xenocrysts of resorbed anorthoclase. aegirine and occasionally quartz may occur. 10. Alkali Limburgite ('Woodendite') - Analysis 27. The anomalous rock from Old Racecourse Hill (Golfcourse Hill), Woodend, differs from the limburgites only in its high alkali content. It is a brown glass containing phenocrysts and clots of olivine. monoclinic pyroxene, and corroded enstatite. PETROGENESIS. Newer Volcanic differentiates have developed on parallel trends in separated areas and' at irregular intervals during the period of volcanicity. To explain this Edwards ( ) visualised differentiation occurring in independent cupolas rising above the main magma chamber. Extrusion of differentiated material would then precede the widespread outpouring of unmodified basalt. The petrogenesis has not yet been revised to take account of more recent knowledge. He considered that the labradorite basalts approached most closely to the parent magma, with an approximate composition - Si02 500/0, Al /0, total FeO 11.50/0, MgO 8.50/0, GaO 8.50/0, Na20 30/0. K /0 - which indicates relatively high silica and alkali. He explained the production of alkaline types in terms of the gravitational separation of early formed minerals. with the initial crystallization of olivine depleting the magma of magnesia relative to lime. later joined by diopsidic pyroxene to leave a residuum enriched in silica. alumina. and alkalies. He also pointed to the early crystallization of anorthoclase and aegirine which became incorporated in more basic layers either by downward convection or by incorporation from the periphery of the cupola during extrusion. The occurrence of small volumes of limburgite he explained by the crystallization and flotation of calcic plagioclase before pyroxene began to form. resulting in an ultrabasic layer overlying unmodified primary magma. The residuum would be enriched in pyroxene and retain its alkalies. a feature of these limburgites. The hypersthene-bearing basalts and trachyandesites. occurring at Mt. Gisborne and 24 mile s to the NW at Spring Hill. are anomalous in an olivine basalt - trachyte suite. Edwards pointed out that with 500/0 S:02 local assimilation of sialic material would readily render the primary magma saturated with silica and cited the presence of quartz xenocrysts in these rocks in support of this. Crystallization and removal of hypersthene and calcic plagioclase on a tholeiitic trend would explain the development of the trachyandesites in whi,ch both of these minerals occur as resorbed phenocrysts.
113 98 Leave Melbourne through Essendon. ITINERARY LOCALITY 1 - Bayview Quarry. Tullamarine (13 miles). Older Basalt showing narrow columnar jointing with varied orientation. overlain by nonmarine Tertiary sands locally cemented. capped by Newer Basalt. Pas s Bulla (16 m.) - kaolinized granodiorite in Deep Ck. valley; Sunbury (22 m. ~ LOCALITY 2 - Near Red Rock (27m.). View of basaltic volcanic hills (Fig. 1) and of Mt. Gisborne. LOCALITY 3 - N. slope of Mt. Gisborne (32m.). Hypersthene trachyandesite with norite and hypersthene basalt xenoliths. View of Mt. Macedon range. noting Camel's Hump and trachyte flow through Upper Macedon. LOCALITY 4 - Turritable Falls. Uppe l' Macedon (39 m. ). Anorthoclase trachyte of Upper Macedon flow. shown by Bahat to vary in composition from bottom to top. Twin lateral streams of Turritable Ck. on W. Willimigongong Ck. on E. Ascend Mt. Macedon to LOCALITY 5 - Memorial Cross. Mt. Macedon (3.301 ft.) (43 m. ). Hypersthene dacite. View to S of Mt. Gisborne. Mt. Bullengarook and other volcanoes, with Werribee Plains in distance; to SW domal uplift of early Tertiary surface; to W. NW basaltic valley flows separated by low Ordovician ridges. LOCALITY 6 - Camel's Hump (3.317 ft.) (46m.). Quarry in soda trachyte with flow banding. Descend N side of range to Woodend (52 m.). LOCALITY 7 - Old Racecourse or Golfcourse Hill. Quarry in alkali limburgite ('woodendite'). LOCALITY 8 - Hanging Rock (2,353 ft.) (57m. ). Soda trachyte mamelon with prominent vertical jointing. View to NW of Mt. Alexander (2.435 ft.) granodiorite - to N of Cobaw ranges. and The Jim Jim (2.446 ft.) anorthoclase trachyte dome capped by andesine basalt which flowed down SE flank - to NE is anorthoclase trachyte hill in foreground. Mt. William (2.639 ft.) and strike ridge of Cambrian greenstones in distance - to E is Brock's Monument soda trachyte - to S is Mt. Macedon range with Camel's Hump. LOCALITY 9 - King's Quarry. Hesket (58m. ). Quarry in lirnburgite showing nodular weathering. IN TRANSIT. Travel through Newham (61 m.). pass old diatomite workings (63 m.) and McAlister's Rock on left to Rochford (66rn.). LOCALITY 10-1 m. NE of Rochford. Oligoclase trachybasalt. IN TRANSIT. Travel to LancefieJd (71 m.). Melbourne Hill on left - olivine basalt and limburgite overlying oligoclase trachybasalt flows. Pass Rocky Range andesine basalt on right. to Romsey (76m.). View of Mt. William range on left. Macedon range on right with ridges of Kerrie Conglomerate and trachyte dome of Mt. Eliza (2.320 ft.). Pass Monegeetta (81m.) to LOCALITY 11 - Emu or Bolinda Ck. bridge (85m.). Iddingsite labradorite basalt. Return to Melbourne through Bulla and Essendon..' ~I I ~,'
114 99 REFERENCES Bahat. D Some Mineralogical. Geochemical and Petrological Aspects of the Tertiary Alkaline Province in Victoria. Unpubl. Thesis. Univ. of Melbourne. Crawford. W The Physiography of the Gisborne Highlands. Proc.Roy. Soc. Vic. 52{2} : Edwards. A. B Three Olivine Basalt-Trachyte Provinces and some Theories of Petrogenesis. Ibid. 48{1} : Edwards. A. B The Tertiary Volcanic Rocks of Central Victoria. Quart. Journ. Geol. Soc. London, 94(2): Edwards. A. B Petrology of the Tertiary Older Volcanic rocks of Victoria. Prbc. Roy. Soc. Vic.,51{1} : Edwards. A.B -and Crawford. W The Cainozoic Volcanic Rocks of the Gisborne District. Victoria. Ibid 52{2} : Harris. W. J. and Crawford, W The Relationships of the Sedimentary Rocks of the Gisborne District. Victoria. ~. 33 : Skeats. E. W. and Summers. H. S The Geology and Petrology of the Macedon District. Bull. Geol. Surv. Vic., No. 24. Thomas, D.E The Kerrie Series and associated Rocks. Proc.Roy.Soc.Vic 49{2}: e.i... -n.... CLIFFS A.W ISLETS WEST OF, PRmCETOVvN I C1U'.E OTW/cr DISTRICT C.S.1I/.ilIWI.401t - J1Jr.og. Rep. Geo!. Swtv. Vie 'j,',
115 100 CHAPTER 12 GEOMORPHOLOGY OF THE WESTERN DISTRICT VOLCANIC PLAINS, LAKES AND COASTLINE INTRODUCTION. by C.D. OIlier and E. B. Joyce Volcanic rocks of the western Victorian volcanic province are known as the 'Newer Volcanics' to distinguish them from the 'Older Volcanics' which are found mainly in Gippsland, eastern Victoria. The Older Volcanics are Lower Tertiary and only eroded remnants are left. The Newer Volcanics are Late Pliocene to Holocene in age. The pre-volcanic topography cannot be precisely defined as the volcanics were erupted over a long period of time, but the broad outlines are clear. The Otway ranges of Mesozoic rocks and the Coastal Plains of Cainozoic sediments lie to the south. North of these the Western District Plains are underlain by Tertiary sediments, and once contained extensive lakes. Lake Corangamite and its neighbours occupy depressions on the site of what was once a much larger lake (Currey, 1964). To the north of the plains the Western Highlands consist of a dissected plateau of Palaeozoic rocks. This slopes down to the north and is eventually covered by the sediments of the Northern Plains. These divisions are shown in Fig. 2. Onto this topography the volcanics were strewn, but there was considerable tectonic movement both during and after volcanicity. The Brisbane Ranges are bounded by the postvolcanic scarp of the Rowsley Fault which has a throw of several hundred feet. Elsewhere monoclines warped the volcanics without faulting, as in the Geelong district. Many of the large valleys were blocked by lava flows, and drainage ponding and diversions caused further modification to the landscape. The result is that at the present day the basic physiographic features remain - Coastal Plains, Volcanic Plains, Western Highlands - but are now diversified by primary volcanic landforms (cones and flows) and by landscape modifications attributable in part at least to the volcanic activity. DISTRIBUTION OF LAVA AND VOLCANOES. Fig.l shows the extent of Newer Volcanics in western Victoria, and Fig. 3 shows the distribution of the main points of eruption. There are a great many small points of eruption without names, some being insignificant, and as it is impossible to show them all, only named volcanoes are included in Fig. 3. This volcanic province is remarkable in having a large number of points of eruption, none of which grew to any great size; very few are over 500 ft. above their base and most are less than 300 ft. These hills mark points of eruption that poured out large quantities of lava as sheet flows and confined flows; the hills, though very eye-catching, represent a very small portion of the lava erupted. OIlier and Joyce (1964) calculated the explosion index, E, which is the percentage of fragmentary material in the total volcanic material produced, as only 10/0. This can be compared with 30/0 for the Pacific, 390/0 for Iceland and 950/0 for island arcs. Volcanoes take the form of basalt cones, scoria cones, maars, and complex types. Lineaments are few, and central type eruption was dominant. Physiographic features of lava flows, such as tumuli, stony rises and lava caves are well preserved on the younger flows. Volcanicity of the Newer Volcanics commenced in Victoria in the late Pliocene. ranging from 4.5 to 0.57 m. y. have been obtained (McDougall, Allsopp and Chamalaun, 1966). On the older flows extensive weathering and soil development has occurred. Scoria cones were later built up in the highlands and towards the south of the plain, and later still the maars erupted. Activity continued into the Holocene, with a number of valley flows and areas of Stony Rises. The relevant radio-carbon dates are summarised by Gill (1971). Ollier (1967, 1969) and Singleton and Joyce (1969) give general accounts of the volcanicity. Reprinted with permission from REGIONAL GUIDE TO VICTORIAN GEOLOGY. Edited by J. McAndrew and M.A.H. Marsden, 2nd Ed., Ages..
116 101 DISTRICT PLAINS Co mperdown o MILES Fig. Z. Geomorphic regions of western Victoria. N I.. : t : :... Fig. 3. Newer Volcanic points of eruption.
117 , 102 Cotteril f THE COAST. From Portland to Warrnambool the lava plain reache s in place s to the coast. Further east. between the southern edge of the lava plain and the Otway Ranges. Miocene limestone and marl form the surface. A lime stone sinkhole plain and a dissected seaward- sloping marl surface end at the coast in steep cliffs. ITINERARIES I Melbourne-Geelong-Inverleigh-Lake Corangamite-Lismore-Derrinallum Mortlake-Penshurst-Hamilton. Lava plain, laterite, lakes. volcanic cones. 2 Hamilton-Byaduk-Macarthur-Port Fairy Warrnambool. Valley flow, lava caves, lava blisters. lava channels, spatter cones. stony rise s, aeolianite coast. 3 Port Fairy-Warrnambool. Nested maar. 4 Port Campbell Limestone plain and coastline, emerged platform. rises Lake Cundare Fig. 4 (upper). Melbourne to Geelong. Fig. 5 (lower). Area at north-east end of Lake Corangamite. with lunettes stippled. 5 Port Campbell- Camperdown-Colac Winchelsea-Geelong. Lava plain. maars, stony rises, lakes, volcanic cones, convex hills lope s. 1. MELBOURNE TO HAMILTON. Werribee Plains. The journey from Melbourne to Geelong is largely across the Werribee Plains. made of wide sheets of Pleistocene basalt. A few volcanic mounds. the points of eruption of the lava, can be seen to the west,. including the three scoria mounds called The Anakies (Fig. 4). The largest group of hills, the You Yangs, are granite hills projecting through the basalt. Beyond the Anakies are the Brisbane Ranges, marking the line of the Rowsley Fault Scarp over part of which the basalt flows are monoclinally folded.. Halfway to Geelong the highway crosses a triangular patch of alluvium known as the Werribee Delta, here about six miles across. The river has cut into the delta sediments, forming terraces and vertical cliffs. At Hovell's Creek, marine shell beds about five feet above sea level have been dated at 5,620 :!:. 90 B. P. They overlie bored freshwater limestone of Pleistocene age (Gill, 1971). Geelong is a major port on Corio Bay, which was partly formed by down-faulting. The Barwon and Moorabool Rivers have cut into the. lava flows on which part of Geelong is built, and river terraces are developing.. The road to Hamilt'ln continues acruss 1:he basalt plain, which now b~comes the Western District Plain. A road cutting three miles west of Inverleigh shows the lava overlying Pliocene sedim~nts on which a lateritic podsol had developed. '. ','ig. 1. (opposite). Geological map of south-western Victoria.
118 '-~-- eedennope ' , -,1- - BAY Quaternary Tertiary Mesozoic Upper Palaeozoic Lower Palaeozoic {I=--_-I Seaiments.:.:.:.:.:.:.: Newer Volcanic '~:;:';;1'j'::~0t..-:.~ Seaiments (m.'ne an a non,ma'ne ' ) I' 'II' 'I Olaer Volcanic I:.,' :...'.. :1 Arkose, sanaslones ana muasfones I /,' ~ -; 1 ~/ I Glacial seaiments, s.nasfones rhyo/ifes efc. {r '' ' ~ Mefamorphics. s/.fes ana sanasfones... '... ' ~ SCALE OF MILES o BASS Prepared by Deparlment 01 STRAIT
119 103 o 1 L ' Miles /I Fig. 8. Distribution of lava blisters, Wallacedale. See Fig. 7. ~ig. 7. Hamilton to Port Fairy, showing the most recent volcanic activity. Fig. 9. Range of variation among tumuli. Inverleigh Former ~ Present Lake Corangamite 4 L--.J miles N i Fig. 6. Former extent of Lake Corangamite Lake Corangamite. There are numerous lakes on the Western Plains, on the site of a former, much larger 'Lake Corangamite' (Currey, 196 4,) (Fig. 6). The old lake shore is marked by a terrace at a consistent level of 396 ft., which is at least 10 ft. above the present beds of the various lakes. The small lakes have lunettes - crescentic dunes of lake-derived, wind-blown material - on their eastern shores. As the former lake shrank, a succession of terraces and lunettes was formed and abandoned.
120 104 ~ r----:;;r- : :7'----'---'---'--'--- l~ we o , yards ~ Fig. 10. The Byaduk lava caves. 1. Harman Caves, 2. Bridge Cave, 3. Church Cave, 4. The Basin,S. Flower Pot, 6. Bathtub, 7. Shephard's Cave, 8. Tunnel Cave, 9. Fern Cave, 10. The Turk, 11. Staircase, 12. Brown's Cave. For location, see Fig r:=:~~c:-~-~----~ 0~100 feet Fig. 11. Church Cave. At Point A, Fig. 5, a cross-section of an old lunette may be seen, and at Point B some present day dune fonnation can be observed. Here the features are made of Coxiella shells, and sand drifts, sand shadows, blowouts, ripples and other aeolian features can b~ observed in action. Mount Elephant at Derrinallum is the highest (780 ft.) and most perfect scoria cone on the We ste rn Plains. 2. HAMILTON TO WARRNAMBOOL. Mount Napier. This scoria cone south of Hamilton is at the source of the Harman Valley lava flow, which is 15 miles long and only.300 yards wide at the highway north 'of Byaduk (Fig. 7). This is one of the youngest flows in Victoria, a radiocarbon date from Condah Swamp indicating Holocene (Gill, 1971). Of particular interest are the Wallacedale 'lava blisters' near the end of the flow (Fig. 8), and the Byaduk lava caves, nearer the volcano. Lava 'blisters' take many forms - see Fig. 9 - and are often about 10 ft. high. Skeats and James (1937) interpreted them as gas cupolas formed by steam generated where lava flowed over swamp. OIlier (196-la) interpreted them as exaggerated forms of tumuli, pushed up by lava...
121 105..._'-..,.--.,..- ~t c', ,',' ..._ '.,9,',;' I I I...,' ',-' <.po, I I I / I 1/ /1 / I I 1 I 1, :c, I,/ / I I _, / I I I I I I I I I I I I I I / I I I I I I.0 miles To... (' ~... ~'-/ _. ' C. Db. Fig. 12. Location of caves at Mount Eccles. t, Tunnel Cave; c, canal; L.S., Lake Surprise; Mt.E., Mount Eccles summit; g, Gothic Cave; s, The Shaft; p, The Pit; a, The Alcove. Fig. 13. The Shaft. Vertical exaggeration 2 1/2 times. The Byaduk caves (Fig. 10) follow the centre of the flow, above the first point of constriction (OIlier and Brown, 1964). The entrances are all due to post-cooling collapse. 'Layered lava', due to streaming flow within the lava, is exposed on walls. Within the caves are numerous collapse s, lava stalactites, pahoehoe floors, etc. Church Cave is the largest in the group, and the most complicated (Fig. 11). It appears that after the first Church Cave was formed, the floor solidified for about three feet below the surface, but beneath this skin the lava was still hot and liquid. At a later stage this liquid was also withdrawn and the floor collapsed into its present form, with spaces amounting to small caves below. At the western termination of the cave is a small pipe leading down to a lower level of the cave, and nearby is a small, high level lava conduit of the same shape as a small lava tunnel. Its supply of lava was evidently cut off by the formation of Church Cave, and some of the lava already in the pipe dribbled down the wall as 'entrail' lava. The two sinkholes of Church Cave are joined by a typical tunnel. In brief, the caves are formed by draining of hot liquid lava from beneath a solidified, cold crust. This simple explanation cannot account for all the details of cave plan, cross section and other features. A more complete description and explanation is given in OIlier and Brown (1965). ' Ivlount Eccles (Fig. 12). '. Mount Eccles is the highest scoria mound on a large volcanic complex that includes Lake Surprise (an elongated crater lake), lava channels or 'canals', a number of scoria and spatter cone s, lava cave s. and large basalt sheets and flows. The Tyrendarra flow was at least 30 mile s long and disappears below sea level; it is similar in many respects to the Harman Valley flow (Fig. 7). Canals mark lines of drainage within the lava sheets. Lava flowed along and beneath the canals, occasionally over. spilling and raising the general level of the basalt sheet by a process analogous to levee buildin6' Side flows run almost perpendicular to the canal, and Tunnel Cave is presumed to be in such a lateral flow. In the floor of the northern canal is a small tumulus or lava bliste r. Gothic Cave is an exceptional lava cave, being in line with a canal although the ground above the cave is flush with the surrounding plain. Contortions in the layered lava within Gothic Cave and the shape of the cave cross section suggest distortion while in a plastic state. '.
122 106 A number of points of eruption are clearly aligned, and also in line with the length of Lake Surprise, which may be evidence of fissure eruption (Boutakoff, 1963). It is also possible that the cones are adventitious volcanoe s along a straight lava flow (Ollier, 1964b). 'The Shaft' (Fig. 13) is a spatter cone with an open vent that extends below the level of the surrounding plain, and widens at depth in a patch of frothy rock. 'The Pit' and 'The Alcove' are geologically similar, though less spectacular. 3. PORT FAIRY TO WARRNAMBOOL Western District Coastline. From Port Fairy to the Otway Range s the coastline divide s into three main parts (Gill, 1947) (Fig. 2) - I N 1. Port Fairy to Warrnambool : mobile dunes. 2. Warrnambool to Childers Cove: aeolianite dune s, with cliffs from 100 to ft I 200 ft. high. 3QQ A 3. Childers Cove to near Princetown : Miocene Port Campbell Limestone with cliffs to 200 ft. topped by calcareous and siliceous sand in places. East of Princetown shore platforms and steep cliffs are developed in the Mesozoic rocks of the Otways. Port Fairy. Formerly called Belfalit, Port Fairy is a fishing port built ona headland of basalt which infills eroded Miocene bedrock down to at least 80 ft. below sea level. Marine shells, including the warmer water Ninella torquata, have been deposited on the basalt and dated at greate r than 35,000 (radiocarbon) and at 120,000 B. P. (ionium) (Gill, 1971). The basalt forms shore platforms at the present coast, and in places is overlain by calcareous dunes. ~gg~, I I I , N 1 ':.' Fig. 14. Fig. 15. miles Tower Hill in plan. Tower Hill cross section. Fairy Q 5. B 1 I --~...,... Warrnambool Warrnambool. Fig. 16. Distribution of ash around Tower Hill. Warrnambooi. is built on the top of calcareous aeolianite at 160 ft. above sea level. The aeolianite extends down to 67 ft. below sea level, where it lies on Miocene limestone which rises inland to form a cliff marking a possible Pliocene shoreline (Gill, 1943). Between the town and the sea lies Lake Pertobe, cut off by Holocene coastal dunes. The swamp deposits of the lake cover a beach deposit resting on the aeolianite, and dated at 5,850:t. no B. P. Similar deposits up to l4t ft. above sea level occur along the Hopkins River to the east. An aeolianite platform extends t mile offshore. The aeolianite contains up to five buried soils. It was formerly quarried for building stone, and the footprints of giant birds are recorded in the rock.
123 107 Occasional earthquake shocks have been recorded, and two shocks in 1903 damaged local buildings and cemetery monuments (Hills, 1940). o 10 o,'!'.o o 1;10 '/ Tower Hill. - --'l. 0' o ' j ' Maars are explosive volcanoes with '- broad craters and low rims that merge --- gradually into the surrounding plain. Numerous examples are found in the Western District, such as Tower Hill (Figs.14,15), N Bullenmerri, Gnotuk, Leura and Purrumbete. Peterborough Tower Hill is about a mile across, S, 10, with excellent exposures of pyroclastics around the edges. The beds of pyroclastics 1-...::. 'LES _ dip at low angle s away from the centre, with frequent cross bedding due in part to aeolian sorting. A number of Victorian maars, including Tower Hill, Mt. Leura and Mt. Warrnambool, are nested, with a hill or complex group of scoria hills inside an older maar. It seems that the first eruption on such site s was violently explosive, forming the maar, and the final eruptions were more gentle, forming scoria cone s. A wide area was covered by volcanic ash during the eruption of Tower Hill, and its distribution is shown in Fig. 16. Gill (1950, 1971) suggested that the distribution indicates a south westerly wind, consistent with the winds of the present climatic regime and the youth of Tower Hill (5500 to 6000 years). However, the distribution may be related to unusual winds during the comparatively short period of eruption, and small patches near Warrnambool shows that the distribution is not very easy to define. Camperdown o - -(fr',. LQ:'b--,r o o ~ :,Cobden o I, ;1, I ( ~ I, I ~' Port Campbell --', Princetown '. Fig. 17. Western District coast and distribution of maars (circles). N I, Curdie I S a Inlet u, C) 0 1'4 1~ Q ~, 0 Mile. ~ Fig. 18. Peterborough and Curdie's Inlet showing sinkholes and rock stacks. The pyroclastics of maars vary from dominantly bedrock to dominantly igneous. Tower Hill maar is made up of igneous pyrodastics, mostly lapilli and ash, with occasional bombs. Gill (1967) has described the Tower HIll area in detail. 4. LIMESTONE COASTLINE OF THE PORT CAMPBELL AREA A limestone plain 150 ft. above sea level stretches from near Warrnambool to Port Campbell (Fig. 17). Numerous sinkholes up to 300 yards in diameter have developed and surface drainage is absent. Heathland and low clumps of drooping she oak (Casuarina stricta) and brown stringybark (Eucalyptus baxteri) grow on the surface cover of residual day and siliceous sand. Eastwards, the Port Campbell Limestone is found in the cliffs and for about two miles inland. Behind this narrow coastal strip the underlying Gellibrand Clay emerges and rises inland to over 600 ft., forming a highland dis sected by structurally controlled drainage. The Port Campbell Limestone and the Gellibrand Clay belong to the Heytesbury Group of Miocene age (Ch. 13)
124 108 A generalized cliff-section, fro:m the top down, is (Baker, 1944i:- 2-20ft. brown residual clay, 6% soluble, with buckshot ft. soft yellow and whitish li:me stone, 80 to 90% soluble, fos siliferous calcareous clays and argillaceous li:me stone 40 ft. bluish-grey calcareous clay, 36% soluble, with a 6 ft. band of hard li:me stone near the base in place s. The Port Ca:mpbell Li:mestone is thinly bedded, with concretions and secondary lilljestoge along the bedding, and dips of 1 to 5 seaward. Jointing is prominent striking NW- SE (parallel to the coast), NE-SW (controlling gorge and pro:montory formation) and both ve rtical and at 45 0 (controlling cliffs, cave roofs and arches). o N 1 MILES Fig. 19: (above) and 20 (below). Sketch map and generalized cross section of Two Mile Bay (after Baker and Gill, 1957, and 1966 Geomorphology class mapping). t - talus; s - dune and beach sand; c - clay; p - emerged platform and old beach deposits; D - position of carbon-dated shells. The coastline runs NW -SE, but is crenulated with gorges, small bays and promontories. A platform extending up, to % mile offshore has reefs and rock stacks, and Baker (1943) recorded 24 stacks in the six miles between Port Campbell and Castle Rock. Cliffs are close to vertical, and include sections which ove rhang up to 8 0 Generally the cliffs are between 100 and 200 ft. high, and hanging valleys left by the rapid retreat may be up to 150 ft. above the sea. Wavecut benches and notches are found at LWM- 50 to 60 ft. above sea level - E6J stripped zone 30 to 40 ft. above sea level - with rockpools 20 to 30 ft. above sea level - with rockpools 5 to 6 ft. above sea level - 15 to 20 ft. wide. 100 ft p c '- 0, lop It The top bench is formed where the residual clay is stripped by spray, rain and wind. action, leaving an exposed surface with accretions, basins and solution pipes (Baker, 1958). Fortyfive caves are recorded at the cliff-base with several about 20 or 30 it. above sea level (Baker, 1943). Collapse of caves helps to form bays and gorges. The local rainfall is 21 to 45 in. and falls mainly from May to October, so that small streams dry up in the summer. Currents for most of the year are to the east, but from January to March run to the west, and build sand barriers across the mouths of the creeks. Storms are mainly from the southwest, and swell periods of 14 to 16 seconds are most common. The mean rise of tide in Port Campbell harbour is 4 ft.
125 109.. II PINE N..../5 r 1 ~ Legend Caves Sink Holes Fluted Cliffl Dismembered V.lleys Beach Ridge }-RECENT Dune Sands Dune Limestone-PLEISTOCENE Limestones, Clays-TERTIARY 2 3 SCALE OF MILES -.. WEST p.t.!...., 2mls Pb PC ShR Pl Fig. 21 (upper). Map of the limestone coastline (from Baker, 1943). Fig. 22 (lower). Coastal section after Wilkinson (from Baker, 1944), P-M - Post-Miocene; Mz - Mesozoic; Pb - Peterborough; PC - Port Campbell; ShR - Sherbrook River; Pt - Prince town. EAST Pleistocene aeolianite is not found along the coast between Childers Cove and Princetown. Holocene calcareous dunes occur at Peterborough and Sherbrook River. The beaches are calcareous sand, 700/0 soluble, and include quartz grains from the Me sozoic rocks to the east as well as locally derived material. Baker has collected and described tektites (small, glassy meteorites) from this area over many years. A recent excavation at Port Campbell suggested a late Pleistocene to early Holocene age (Gill, 1965). The first settlement in this area was in During the 19th Century the rugged coastline was the site of many shipwrecks. The limestone coastline was proclaimed a National Park in May, Detailed Description of Localities (Fig. 21). Peterborough (Fig.18) : west side of Curdie's Inlet, a drowned valley formed in a broad, shallow syncline (see Fig. 22) and often cut off in summer by a sandy barrier. Cliff shows solution and stripping. Platform extends ~ mile offshore, with Schomburgh Reef to the east of the entrance. A series of large calcareous dune ridges up to 100 ft. high form the eastern headland. The Grotto: dissected sinkhole opening onto the cliff through an archway, and containing a boulder beach 40 ft. above sea level.
126 110 tift!, Bullenmerri Fig. 23. Bullenmerri and Gnotuk. T - Tertiary sediments; v - basalt; A - alluvium; stipple - tuff. London Bridge: double arched headland, with a 60 ft. block on the beach to the west which fell before Marble Arch : floor 20 ft. above sea level. Two Mile Bay: an emerged marine platform about 1 mile west of Port Campbell (Figs. 19, 20). A modern platform about ~ mile wide is forming at present sea level. On the indurated surface of the old platform are shelly beach deposits, buckshot, and cemented crossbedded sand. A calcareous dune on the platform has moved inland over swamp deposits of black clay. The fossil cliffs have declined to 30 to 40 0 and deposited talus on the platform. A section through the talus and beach deposits gave shells of Ninella torquata. a species now found further north in warmer waters, which were found to be beyond the range of radiocarbon dating (greater than 30,000 years). Baker and Gill (1957) suggested a late Pleistocene age for the platform. Port Campbell: Port Campbell Creek is in a drowned asymmetrical valley. Point Sturgess on the east is 70 ft. high, and West Head rises up to 200 ft. inland. Reefs extend offshore, and a channel has been cut to 50 ft. or more below sea level. A sand barrier across the creek causes flooding, giving marshy flats along the valley. Slumping occurs on the steep east-facing valley wall., Beacon Steps: two wave-cut benches, cliff-top stripping. Sentinel Rock: rock stack elongate NE-SW. Landward slope 52 0 Goudie's Lookout: narrow promontory 200 ft. high, over 500 ft. long, and 20 to 40 ft. wide. Caves on both sides. The Amphitheatre: due to cliff-top stripping in the head of a hanging valley. Cliff overhangs up to So. Baker's Oven Rock the name. a stack with a tunnel 20 ft. above sea level, from which come s Sherbrook River may have a sandy barrier across its mouth. Sand piles up to 100 ft. high against the cliffs west of the river. The sand is vegetated in some places and elsewhere the surface is cemented. -j N.
127 III N SCORIA. CINDERS AND TUFF II i 11I111 DENSE SASAl.T FELSPATHIC BASALT, -=a MILE Fig. 24. Plan of Mt. Porndon and ring barrier (Skeats and James, 1937). Broken Head: promontory with headland bay. 4 storm benches. and pronounced cliff-top stripping up to 90 ft. above sea level. Survey Gorge: long and narrow. developed along closely spaced joints. Overhanging cliffs. The Blowhole: collapse 45 yards long and over 50 ft. deep in a cave which extends for ~ mile inland from the cliff face. Joint control. Mutton Bird Island: large rock stack. overhanging in part. and a nesting place for mutton birds. Loch Ard Gorge : developed along close jointing. with a narrow entrance but widening to form two small bays separated by a headland. Sandy beaches and vegetated dunes and three caves with stalactites. Carmichael1s Cave. in the weste rn wall. has formed sand stalagmite s by cementing the loose sand on its floor immediately below the dripping stalactites. The cave at the head of the we ste rn bay has stalactite s and stalagmite s joined to form pillars. Pearce's Cave. at the head of the eastern bay. receives the discharge from a gully-fed sinkhole above. and so has a rocky floor (Baker. 1942). The cliffs. less than 100 ft.. show stripping. Masses of foam collect in the gorge and blow onto the cliff face s. On the cliff top above the Gorge is the Loch Ard cemetery. The Loch Ard was a three-masted iron clipper of 1623 tons. which was wrecked on the rocks outside the Gorge on June 1st Eva Carmichael, a passenger. and Tom Pearce. a sailor. survived by reaching the beach in the Gorge. east. Island Archway arched rock stack to the The Bay of Islands: a number of rock stacks with prominent basal notches. and another notch about halfway up. along which some stacks have been planed off by storms. while others remain complete even to the clay capping. The Twelve Apostles: rock stacks extending from Yz mile east of the Bay of Islands to just beyond Castle Rock. The taller stacks are about 150 ft. high. Castle Rock: promontory 600 ft. long. 8 to 30 ft. wide. and 50 to 100 ft. high. Dismembered valley on the top. and talus, tied stack. sandy beach and dune on the western side. 5. PORT CAMPBELL TO GEELONG. The road from Port Campbell to Cobden is over the Gellibrand Marl. with Port Campbell Limestone a few miles to the west. A large area of forest has recently been cleared at Heytesbury for soldier settlement. Trace elements are required to make the soil productive. A few mile s southeast of Cobden, parallel valleys have developed in the marl. The township of Cobden is on the southern edge of the basalt plain, and from here to Camperdown most of the maars are found (Fig. 17). Bullenmerri and Gnotuk. Bullenmerri and Gnotuk (Fig. 23) are lakes in maar depressions. 'but rather more complicated than the usual maar. Gnotuk is a simple circular lake. but the shape of Bullenmerri
128 112 suggests that it is a coalescence of two craters. Bedrock of Miocene sediments is found around the lake shores in a number of places, but Inost of the surrounding walls are of pyroclastics or basalt. Mapping by the 1966 GeoInorphology Class of Melbourne University showed that the basalt sheet is alinost continuous around Gnotuk and runs along the eastern wall of Bullenmerri. The tuffs downslope from the basalt are somewhat contorted, but those above the basalt are nearly horizontal. It is possible that the basalt could have been erupted from nearby volcanoes such as Mount Leura, and the tuffs deposited when the maars of Gnotuk anc;l BullenInerri were punched through the basalt. There also appears to have been warping of the basalt, if it was originally near horizontal as is likely. To the south of BullenInerri is an even older, nested Inaar, called Bostock Hill. The surface of BullenInerri is at 482 ft. and Gnotuk at 345 ft., but both reach bottoin at about 280 ft. Bullenmerri overflowed into Gnotuk in the 1840s or 1850s, and an overflow channel is cut through the riin between the two lakes. Gnotuk is also said to have overflowed to Lake Colongulac. Since 1850 there has been a steady fall in lake levels at an ave rage rate of 7Yz inches a year, due to climatic change. Numerous shore terraces are preserved around the edge of both lakes. Tree stumps are emerging from the water. so there has been even lower water in the past. A recently emerged stump has been dated at 1865!. 85 B. P. (Gill, 1971). The water in Bullenmerri is brackish; it is stocked with trout, and Coxiella shells are plentiful on the beach, and in beach rock. Gnotuk is three times as saline as the sea. Mount Leura is a nested maar, though in this case the maar rim is a very minor feature and the central scoria cones are dominant. Exposures in the scoria reveal interesting structures, and a fine view of the region is gained from the lookout on top of Leura. Purrumbete is a near perfect, simple maar. The rim is highest to the east and nearly absent on the west, and quarry sections display fine sections in pyroclastics. In these sections besides the usual gently outward dipping tuffs there are some inward dipping ones with interesting depositional structures. The steep rim of the crater has been cliffed by lake erosion. Mount Porndon (Fig. 24), is a very unusual volcano. It is the probable source of the widespread 'stony rises' that extend for miles about, due to the earliest eruption. Next there was a lava disc - a sheet of lava about 2 miles across, and perhaps 30 ft. thick, with a distinct, walllike 'ring barrier' formed at the edges, analogous to the 'toe' of linear flows. Numerous depressions of 'stony rises' type are found within the barrier. Finally there were flows of dense basalt, and numerous scoria cones were formed. Scoria is well exposed in Harrison's pit. Many bombs of basalt' peridotite, and occasionally lime stone can be collected. 'Stony Rise s' country tends to a plain on a broad scale, but is extremely irregular in detail, with hummocks and depressions, channels and ridges with a relief of about 30 ft. Some rises are individual narrow lobes of lava einerging froin the base of a lava sheet, found especially on the southern shores of Lake CorangaInite. Most stony rises seein to be due to differential draining of lava from beneath the skin of a partly congealed lava plateau, giving rise to sagging of the surface into depre ssions or channels, with accordant often flat summits to the parts that did not collapse. Eighteen miles before Geelong the basalt has been monoclinally warped and a rogd cutting shows basalt overlying lateritized Tertiary sediments, both units being tilted about 30 to the west. The highway passes along the southern edge of the Barrabool Hills, a block of up-faulted Lower Cretaceous arkose partly covered by Tertiary sediments. Stream dissection has formed steep convex hillslopes. At Waurn Ponds, 6 miles from Geelong, limestone quarries were once worked.
129 113 REFERENCES.. Baker, G., Sand stalagmites. Jour.Geo!. 50: Baker, G., Features of a Victorian limestone coastline. Jour.Geo!. 51 : Baker, G., Baker, G., The geology of the Port Campbell district. Proc.Roy.Soc. Vict. 56 : Stripped zones at cliff edges along a high wave energy coast. Port Campbell. Victoria. Proc.Roy.Soc.Vict. 70: Baker, G. and Gill. E. D Pleistocene emerged marine platform. Port Campbell. Victoria. Quaternaria 4 : Boutakoff, N The geology and geomorphology of the Portland area. Geol.Surv. Vic. Mem.22. Currey. D.T The former extent of Lake Corangamite. Proc.Roy.Soc.Vict. 77: Gill, E.D., Gill, E.D., Gill, E.D., Gill, E.D., Gill, E.D The geology of Warrnamboo!. Proc.Rov.Soc. Vict. 55: Some feature s of the coastline between Port Fairy and Peterborough. Victoria. Proc. Roy, Soc. Vict. 58: An hypothesis relative to the age of some Western District volcanoes. Proc.Roy.Soc.Vict. 60: Radio-carbon dating of australite occurrences. microliths. fossil grasstree and humus pod sol structures. Aust. J. Sci. 27: Evolution of the Warrnambool-Port Fairy coast and the Tower Hill eruption, Western Victoria, in Jennings, J. N. and Mabbutt, J. A., Landform Studies from Austr~ia and New Guinea: A. N. U. Press. Canberra. Gill, E. D., Applications of radiocarbon dating in Victoria, Australia. Proc. Roy. Soc. Vic. 84: Hills. E. S The physiography of Victoria. Whitcombe & Tombs Pty. Ltd. Melbourne & Sydney. McDougall, I.. Allsopp. H. L., and Chamalaun, F. H Isotopic dating of the Newer Volcanics of Victoria. Australia. and geomagnetic polarity Epochs. J. Geophys. Res., 71: allier. C. D. 1964a. Tumuli and lava blisters of Victoria. Australia. Nature 202 : allier. C.D 1964b. Caves and associated features of Mt. Eccles. Vict.Nat. 81 : allier, C.D. and Brown. M.C The Byaduk lava caves. Vict.Nat. 80: allier. C. D. and Brown. M. C Lava caves of Victoria. Bull Volcanologique 28 : allier. C. D. and Joyce. E. B Volcanic physiogra>hy of the Western Plains of Victoria. Proc.Roy.Soc.Vict. 77 : allier, C.~ Landforms of the Newer Volcanic Province of Victoria in Jennings, J. N. and Mabbutt. J. A. Landform Studies from Australia and New Guinea' A. N. U. Press. Canberra. allier. C. D Volcanoes. A. N. U. Press. Canberra. Singleton, O. P., and Joyce. E. B., Cainozoic volcanicity in Victoria. Spec. PubIs. Geo!. Soc. Aust. 2: Skeats, E. W. and James. A. V.G Basaltic barriers and other surface features of the Newer Basalts of Western Victoria. Proc.Roy.Soc. Vict. 49: Turnbull. W.D., Lundelius. E.L. Jun., and McDougall, I., A potassium/argon dated Pliocene marsupial fauna from Victoria. Australia. Nature 206 : 816. I.
130 114 CHAPTER 13 MESOZOIC AND TERTIARY STRATIGRAPHY OF THE OTWAY REGION by O. P. Singleton INTRODUCTION. The sequences flanking the Otway Ranges illustrate excellently the Tertiary stratigraphy of Victoria from Paleocene to Upper Miocene. the interplay of depositional environments. and the effects of mild tectonic activity. Three major sequences are exposed in the coastal cliffs between Eastern View and Torquay. in the small depressed areas on the Aire and Johanna Rivers. and in coastal'sections between Moonlight Head and Port Campbell. MESOZOIC - OTWAY GROUP, The Mesozoic Otway Group is exposed in domal uplifts forming the Otway Ranges and Barrabool Hills and was deposited in an east-west trough. limited on the east by the Mornington Peninsula.and passing westward over southern Victoria into the south-eastern corner of South Australia. The southern limit of this trough lies off the coast and has not yet been delineated. but geophysical evidence suggests a basement high parallel and close to the eastern coastline 6f the Otway Peninsula. The Otway Group ft. in the.ferguson1s Hill No.1 well (Leslie. 1966). is an extremely monotonous sequence of fluviatile feldspathic sandstones and. mudstones. identical with the Mesozoic in South Gippsland which is described in Chapter 14. It differs from the latt.er in the absence of workable coal seams and presence in the upper part along the Gellibrand River valley of seams of bentonitic clay. In bores to the west of the Otway Range s the 'uppe rmost 600 ft. (Waarre Formation) consist of clean quartz sandstone with minor mudstone intercalations. Dettmann (1963) has recognised representatives of her Speciosus and Paradoxa microfloral assemblages which she dates as Neocomian to Albian. The latter assemblage is associated with a macroflora typified by the Pteridosperm Phyllopteroides -. (Douglas. personal communication). The Otway Ranges are a bipartite uplift trending NE -SW consisting of an elongate domal structure between Weneleydale and Apollo Bay, and abutting against it near Mt. Sabine an anticlinal arch through Beech Forest towards Moonlight Head. The flanks of these structures are frequently bounded by monoclines 01' faults. That on the south-east of the main uplj.ft was described bv Edwards (1962) who recognised a system of southerly facing monoclines and asymmetric folds arranged en echelon and oblique to the coastline. This zone of more intense folding is compatible with the close proximity offshore of a buttress of pre-mesozoic basement. South of the Castle Cove fault and the Skene's Ck, monocline. the structure is a broad arch; giving gentle opposed tilts on either side of Cape Otway. The effe'ct of these structures in combination has been to preserve Tertiary sediments in depressed areas on the Aire and Johanna Rivers and in Apollo Bay. Elsewhere the Tertiary dips off the flanks of the Otways with only mild angular unconformity.. Subsidi ary structure s occur to the northward in the Barrabool Hills and near Colac. while to the west,uplifts at Ferguson's Hill near Princetown and Flaxman's Hill near Peterborough are mantled by Tertiary sediments. The present expression of these structures dates from the late Cainozoic. However there is evidence of movement in the Otways between Lower and Upper Cretaceous and during the Tertiary. particularly in the Oligocene. UPPER CRETACEOUS. Upper Cretaceous sediments. up to ft. thick. underlie a narrow coastal strip westwards from Princetown. Its distribution parallels that of the overlying early Tertiary rather than that of the Otway Group. indicating movement between Lower and Upper Cretaceous... Fig. 1 (opposite). Geological map of the Otway Ranges region.
131 /, 1--- 0 ~v v v v 0) 0 ToIMB?ONo I 0 0 I., 00 0 I., r. 0 1 or. 0' o ( 0 I 0 0 o 0. /'.,. -~ ' :12-- ~ FERGUSON HILL _ 0 0 L 0 -). '- P-il':rO.y INLET 0 10 />1' o -I'0oib ~.t~ '1'1' D QUATERNARY D 0 0. '.. o 0 0. '. OLDER D m PALEOCENE ~ MESOZOI QUATERNARY NEWER VOLCANICS PLIOCENE NEWER VOLCANICS OLIGOCENE - HIOCENE VOLCANICS - EOCENE C HILES CAHBRLAN
132 115 Taylor (1964) has shown that the Upper Cretaceous represents a complete depositional cycle completed before marine transgression in the Paleocene. It begins with unfossiliferous sandy units overlain by the dark Belfast Mudstone which grades shorewards into sands. The regressive phase is again represented by sands (Paaratte Formation), in the lower part marine but passing up into non-marine beds with thin coal seams. The marine sediments contain foraminiferal assemblages of Turonian and Santonian ages. Macrofossils include echinoid plates, mollusca including Inoceramus, belemnites and fish remains. Glaessner (1964) has identified Hauericeras angustum of early Senonian age. TERTIARY. The general stratigraphy of the Victorian 'tertiary is discussed in the introductory chapter of this volume. In recent years knowledge of the faunal subdivision and correlation has increased considerably. D. J. Taylor (unpublished) has recognised a nearly complete sequence of foraminiferal assemblages, in part based upon Carter (1958) most of which he can date in terms of the world standard. Where suitable environments are present (infrequent before the Upper Eocene) macrofaunas corresponding to each of these have been recognised, either in calcareous rocks when dominated by polyzoa, echinoids, brachiopods and pectinid lamellibranchs, or in clays when dominated by mollusca. These parallel biostratigraphical sequences are not yet complete and are subject to modification. However, sufficient progress lias been made to enable the application of standard time units and the use of local stage divisions has therefore been discontinued. A detailed compilation of the geology of the Otway Basin has recently been undertaken jointly by the Geological Surveys of South Australia and Victoria (Wopfner and Douglas, Eds., 1971). Table 1 is a correlation chart for the three sequences in terms of these faunal assemblages. Uncertain <?ccurrences are shown in parenthesis. Each macrofaunal assemblage is identified by a locality or formation where it occurs unequivocally, and calcareous assemblages are distinguished by' an asterisk. EASTERN VIEW - TORQUAY SEQUENCE. The Paleocene to Lower Miocene sequence is exposed almost continuously in the coastal cliffs between Eastern View and Torquay. The beds dip SE. off the Otways uplift at progressively decreasing angles and regional strike is slightly oblique to the coastline bringing younger beds in towards the north-east. The only interruption to this is a small anticlinal structure at Bird Rock, Torquay(Fig. 3). The Eastern View Coal Measures and marine deltaic Anglesea Sand (Upper Eocene) were followed by a Lower Oligocene partial marine regression during which the diverse Angahook Formation accumulated. In the Late Oligocene, widespread marine transgression led to the d'eposition of aerated limestones and clays which towards the Otways overlie an unconformity. The coastal section has been described by Raggatt and Crespin (1955) and has been studied in detail by the writer. C. Abele has recently completed the mapping of the Anglesea 1 mile map and is currently describing the foraminiferal faunas. Eastern View Coal Measures (including Boonah Sand) (Paleocene -?Upper Eocene) From Eastern View where it rests on Mesozoic with a slight angular unconformity, this unit outcrops in an arc around the nose of the Otways uplift through the Anglesea R. catchment. to Wensleydale, Dean's Marsh and towards Forrest. These sediments, 1,200 ft. thick, are fluviatile pebble beds, sands and clays derived from Palaeozoic rocks, not from the Mesozoic. Granitic quartz and reef quartz pebbles are conspicuous. Soft when newly exposed they have been silicified on the ridges to sandstones and quartzites locally containing plant remains. Brown coal seams are scattered through the sequence. On the coast thin impure seams occur in the basal 300 ft. at Eastern View, and another in the seafloor at the top near Mogg's Ck. (Edwards, 1962). Thick lenticular seams have been mined at Wensleybrae and at Anglesea whe re a new seam is being open-cut for a power station to supply the Geelong aluminium' works. Both the Mogg's Ck. and Anglesea seams are near the top of the formation, thus invalidating Raggatt and Crespin's Boonah Sand, distinguished on its supposed lack of coal seams. An outlier at Benwerrin on the crest of the Otway Ranges has been down-faulted into the Mesozoic and includes thin sub-bituminous coal seams (avo 30'/0 moisture).
133 TABLE I. Correlation of the Tertiaries of the Otway Coast Information from Foraminifera by D.J. Taylor; information from Macrofaunas by O.P. Sinqleton. 0: Age Zonule Zonule Indices Eastern View - Torquay Aire R. - Johanna R. Moonlight Head - Port Campbell Molluscan Assemblages Calcareous Assemblages (.) Upper Miocene Middle Miocene B C o upper limit of keeled Globorotalia spp. Globorotalia m~yeri Orbulina universa D (Lake Connewarre) 17 f B 19 * 20 Beaurnaris Port Campbell Limestone 19 Rosehill C Rutledge's D Glenample Clay (17*) 117 Grice's Ck. 19* Port Campbell 17 * Bairnsdale E Globigerinoides glomerosus gr.--+ Orbulina suturalis (covered) E Balcombe Bay Lower Miocene F G Globigerinoides bisphaericus, (Lepidocyclina) Globigerinoides trilobus trilobus F yellow Bluff Beds - - F Zeally Limestone (restr.) 14 F F Gellibrand Clay G Cellepora Beds 13' I G Fishing 13 I G Fishing Pt. Point Marl 15 * Batesford 14 * Zeally 13 * Cellepora Oligocene Uppermost Eocene Upper Eocene Middle-Upper Eocene H J K L Globigerina woodi --+ Globigerinoides trilobus Globorotalia opima opima, Bolivina anastomosa, Victoriella conoidea Chiloguembelina cubensis, Bolivina pontis --to B. anastomosa Globigerina linaperta, Bolivina pontis Globigeraspis index III H Puebla Clay (restr.) Jan Juc Marl Pt. I 10 I J. Angahook Formation K (L) Anglesea Sand 12 10' Addis Limestone M N Hantkenina alabamensis Hantkenina australis H I K Calder R. Limestone 10* loa Glen Aire Clay B K Castle Cove 7* Limestone L L 6 H 12 I Clifton Formation 11 ' ~ o u c o ~ '..<..< ~ U > ~ - J J KI K Narrawaturk (Ll L Marl 12 Puebla 11 Table Cape 10 Jan Juc loa Glen Aire 9 Lakes Entrance B A.W.1. 6 Brown's Ck.III c M Browrrs Ck. Cla~ ~ ~ (M M Greensand 5.,...j :j Brown's Ck. II N 4 'g 0 (N N Mepunga 4 Brown IS Ck. I 12* Dowd's 10* pt. Addis 7* castle.. Cove 5 * Tortachilla Middle Eocene Lower Eocene o P o ~ (0 0 Form. o u ~?LoWer Eocene or Upper Paleocene Q Globorotalia cf. pseudomenardii Q Princetown Mem. Upper Paleocene R Globorotalia chapmani chapmani Eastern View Coal Measures Johanna R. Sand R 3 A.W.7. Dilwyn Clay s Globorotalia aequa, Lamarckina rugulosa s Rivernook Mem.2 2 Rivernook T Globorotalia angulata -+ G. aequa T T Middle Paleocene u Globorotalia chapmani ehrenbergi, Baggatella Spa v vvv 'VV'. VVV /VV'. vvv /VV Rot ten point Sand I U /VV'-.. VVV /YV'. Pebble Point Grit Pebble Pt. A.W.I etc. Lower Paleocene W are locali ties ot Wilkinson (1865).... #' ~
134 117 Pollen assemblages with Triorites edwardsii indicate a Paleocene age for the lower portion but as yet palynological dating is not available for the upper part. Anglesea Sand (including Addiscot Greywacke). Late Eocene transgression led to the deposition of the marine deltaic Anglesea Sand to 500 ft. of uniform black carbonaceous and pyritic sands. These are fine-grained, wellsorted, with some white mica but relatively little clay component. Bedding though present is difficult to recognise except towards the top. The largely carbonaceous organic matter confers plasticity on the rock which behaves in bulk much like a clay. Associated pollen is abundant, characterized by Proteacidites pachypolus. Pyrite is abundant in the fresh rock as fine-grained friable concretionary masses while large vivianite concretions are washed ashore from the submarine outcrop... The Anglesea Sand, both fresh and weathered, is riddled by branching burrows from which the organic matter was removed. The only common marine fossil in outcrop is the arenaceous foraminifer'haplophragmoides ('Cyclammina' auctt. )which occurs in a decalcified state in every outcrop (Taylor, 1965). In addition Late Eocene planktonic forms have been found in bore samples from near the top of the formation. Other fossils include holothurian spicules, an echinoid, gasteropod, pteropod, and sharks' teeth. Their rarity is due largely to an unfavourable bottom environment but also to the destruction of all carbonate in the acid conditions of outcrop. The preservation of organic matter is indicative of reducing conditions in the newly deposited sediment, but the writer considers that its interment was due to oversupply and rapidity of deposition rather than to complete de-oxygenation at the water interface. An abrupt change in colour occurs at the water table with the rapid oxidation of organic matter. In this weathered zone pyrite oxidizes to iron sulphate minerals of the jarosite group which accumulate in large masses. The final stage in weathering is leaching of sulphate with formation of a thick limonite capping, resembling a laterite, which protects the underlying soft sediment from erosion. Raggatt and Crespin (1955) distinguished the fresh and weathered rock as the Anglesea Siltstone and Addiscot Greywacke respectively, which together with the overlying Angahook member constituted their Demon's Bluff Formation. Irregularities in the junction between fre sh and weathered rock were attributed to unconformable relations, but bedding planes' can be seen passing without interruption from one to the other. With the elevation of the distinctive Angahook to formation status and recognition that the Addiscot is merely weathered Anglesea, the Demon's Bluff Formation becomes a redundant term. The Anglesea Sand outcrops on the coast between Mogg's Ck. and Fairhaven in a full crosssection and in bays on either side of Pt. Addis where, because of greater coastal retreat up-dip, divergent apparent dips have been misinterpreted in the past as anticlines. Angahook F'ormation. Early in the Oligocene marine regression caused the shoreline to retreat to between Pt. Addis and Bell's Headland, during which time the Angahook Formation accumulated. Its stratigraphy is best explained in terms of the entirely non-marine section at Soapy Rocks, Anglesea. It conformably overlies the Anglesea Sand which at its top consists of 6 ft.- thick cross -bedded units with basal strings of quartz gravel and clay laminae at the top. Five depositional units can be recognised. 1. Basal 3 ft. of laminated ciays showing load casts, beginning with a thin black clay previously recorded as brown coal. 2. Bed 6-8 ft. thick, bipartite, the lower unit is a rnudflow deposit containing contorted blocks of basic pyroclastic material and laminated dark siltstone, separated by a sharp irregular junction showing large-scale load casts,from the upper unit of re-sorted water-laid pyroclastic material now weathered: ft. of bedded grey clays and 15 ft. of yellowish bentonitic clay of original sandy texture, showing fine cross-bedding and distinctive scalloped liesegang banding. 4. Thin band of conglomerate including basalt pebbles ft. of mottled ferruginous sandy clays. The pyroclastic material was clearly derived from the volcano at Airey's Inlet of Angahook age, where vesicular basalt showing large columnar jointing forms the base of the cliffs at
135 118 Split Rock. To the north-east as far as Urquhart's Bluff this is replaced by weathered subaerial basaltic agglomerates showing steep initial dips and containing blocks of fresh basalt and of underlying Anglesea Sand. Lenses of bentonitic clay identical with unit 3 at Soapy Rocks infill scours in the agglomerates. Unit 5 is represented by ferruginous sands and clays between Airey's River and Fairhaven. Further northeast at Pt. Addis the Angahook Formation consists of about 50 ft. of sands and clays, the lower part poorly sorted and the upper well sprted, intercalated conformably between the Anglesea Sand and Pt. Addis Limestone. The well-sorted sands represent littoral deposits and pass upwards with intertonguing into the limestone. By Bell's Headland the Angahook has become entirely marine in a conformable sequence and consists of dark clays containing abundant Turritella and some other mollusca, with several intercalated hard bands of grey impure cemented limestone. After a gap without exposure it is succeeded by a 20 ft. tongue of the Jan Juc Marl and then by the Pt. Addis Limestone. The micro-fauna of the Angahook here is early Oligocene in age and marks the l;;lst occurrence of Chiloguembelina. Point Addis Lime stone. In the Upper Oligocene, widespread marine transgression established normal aerated conditions in the Otways region and here the resulting sediments of the Torquay Group are interbedded shallow-water limestones and off-shore clays and marls. The Pt. Addis Limestone, 75 ft. thick, is a calcarenite consisting of fragments of polyzoa and other fossils. Bedding is uneven, with scouring and a prominent diastem in the upper part showing conspicuous erosion of the underlying bed. Cementation is irregular in bands and concretions. At Airey's Inlet, it rests unconformably upon the truncated volcano but further northeast is conformable to the Angahook. The underlying basalt is deeply channelled. with limestone penetrating down joint planes for at least 15 ft. and with basalt boulders embedded in the basal bed. The fauna of this bed includes mollusca and other forms characteristic of rocky sea floors. Upon the pyroclastics it begins with a bed of reworked pyroclastic material and the lower limestone beds contain clastic material including scattered quartz gravel. The fauna is typical of the Te rtiary lime stone s with the echinoids Monostychia australis, Cassidulus florescens. and large Lovenia forbesii as characteristic elements. Jan Juc Marl. Within the one mile interval between Rocky Pt. and Fisherman's Steps, Torquay,the Pt. Addis Limestone passes into the Jan Juc Marl in a superb example of lateral change in facies. The transition is complex in detail with much intertonguing and there is an intermediate facies of finer calcareous clays, in part cemented, in which the carbonate content consists of fines elutriated out of the calcarenite. The fauna,while still of calcareous type. -has changed in composition. The characteristic echinoids are Duncaniaster australiae, smaller Lovenia forbesii. and Eupatagus murrayensis, while Monostychia and Cassidulus are absent. The typical Jan Juc Marl, ca. 120 ft. thick, consists of interbedded glauconitic clays and marls in which the carbonate content is of comminuted autochthonous fossils. Elutriation has produced bands resembling shell grit and layers of concentrated Glycymeris ornithopetra. Selective cementation has resulted in alternating hard and soft bands in the upper part. One of the se hard bands. the Bird Rock Cap, 6 ft. below the top of the formation, is an important marker which can be traced into the Pt. Addis Limestone. The sediments have been extensively burrowed. The base of the formation is not exposed at Bird Rock. Torquay, but may be seen at Bell's Headland. The fauna of the Jan Juc Marl is extremely rich, including giant forms, and marks the beginning of optimum conditions froin Late Oligocene to Middle Miocene which however were temperate not tropical. The mollusca from the very top of the formation correlate with the fauna in the basal grit at Table Cape, Tasmania (T.A. Darragh, personal communication). The foraminiferal assemblage listed by Raggatt and Crespin (1955) froin locality BR 5, just above the Bird Rock Cap, includes Late Eocene species froin a misplaced sample probably froin the Brown's Ck. clay of the Aire R. district.
136 119 Puebla Clay (restricted).. A marked change in lithology distinguishes the overlying Puebla Clay, some 90 ft. of grey clays with thin bands of cemented concretionary limestone. Of these the 2 ft. Septarian Limestone is animportant marker 30 ft. above the base, and the clays just below it contain abundant clusters of pyrite cubes. The Puebla Clay forms the upper part of the cliffs between Bird Rock and Bell's Headland. Raggatt and Crespin (1955) included the succeeding units of differing lithologies within the Puebla Formation, but it is preferable to separate these. Cellepora Beds. This unit comprises about 50 ft. of interbedded calcareous clays and ragged clayey limestones in which fossils have been concentrated to form a polyzoal 'rag'. Colonies of the polyzoan Cellepora gambierensis are abundant. Zeally Limestone (restricted). This term is bes't restricted to the overlying ca. 50 ft. of calcarenite outcropping at Jan Juc Pt. and Pt. Danger. It repeats the lithology of the Pt. Addis Limestone in all details but contains a significantly younger fauna. The echinoid Scutellina patella is abundant and the occurrence of the minute brachiopod Neobouchardia minima from the Late Oligocene and Early Miocene of New Zealand is noteworthy. Yellow Bluff Beds. The youngest exposed beds, some 30 ft. thick at Yellow Bluff, repeat the lithologies of the Cellepora Beds but are less fossiliferous. They represent a horizon little older than the Batesford Limestone. Further eastward,younger beds occur beneath the Lake Connewarre depression culminating in Middle Miocene clays at Campbell's Pt. AIRE RIVER - JOHANNA RIVER DISTRICT. These two small areas of Tertiary rocks on the downthrown side of the Castle Cove fault and Johanna R. monocline contain a Paleocene to Early Miocene sequence intermediate in character between those of Eastern View - Torquay and Moonlight Head - Port Campbell. The sequence has been built up from a number of partial sections particularly those on the coast between Rotten Pt. and the Johanna R., at Castle Cove, and near Hordern Vale (Fig. 2). The non-marine Rotten Pt. Sand is overlain by the dirty marine Johanna R. Sand. Aerated conditions obtained during the Middle-Late Eocene in the conformable sequence of Brown's Ck. Clay, Castle Cove Limestone, and Glen Aire Clay. A mild angular unconformity in the Upper Oligocene was followed by the Calder R. Limestone and Fishing Pt. Marl. The stratigraphy in this district was determined by the writer foraminiferal faunas were subsequently described by Carter (1958). studied the lower portion in detail. Rotten Point Sand. and his father and the Recently D. J. Taylor has Resting unconformably upon the Me sozoic at Rotten Pt. are about 80 ft. of light-coloured cross-bedded sands with pebble beds. Fossils are lacking and they are considered to be nonmarine. Johanna River Sand. 120 ft. of dark carbonaceous sands and subordinate clays follow marine transgression and compare closely in all respects except age with the Anglesea Sand. Taylor (1965) has identified a Late Paleocene assemblage at the base and a Late Eocene one near the top, both dominated by Haplophragmoides, indicating considerable condensation within the unit. At Castle Cove 14 ft. of. the upper part rests on Mesozoic on a monocline associated with the Castle Cove Fault. Brown's Creek Clay. The base of the Brown's Ck. Clay is marked by the onset of ae rated conditions with the entry of rich macrofaunas and planktonic foraminifera. At Brown's Ck. the basal 25 ft. is a black glauconitic clay with Hantkenina australis and an element in the mollusca known elsewhere only from bores at Adelaide. The overlying 4 ft. of pure greensand and 2 ft. of glauconitic clay,
137 120 f ' RECENT G Alluvium QUATERNARY c...::::::i F='''=I TERTIARY ~ ~ ~ ~ F::'l ~ o MESOZOIC Felapathic OLlGOCEJlE-MIOCEN! Dune limestone. aand PALIOCDlE-oLlGOC!N1 Limestone, marl nd.ton~. liud.tone,' Road.. /Fault Shore platfam x Monocline AWl etc. LoCalitie. of Nilkinaon (1865) Fig. 2. Geological sketch map of the Aire River - Johanna River district.
138 121 with Hantkenina alabamensis, carries a specialised macrofauna including Stethothyris pectoralis, Notostrea lubra and Aturia clarkei. The remaining ca. 90 ft. are a variety of clays with a molluscan assemblage in the upper part,which correlates with the Blanche Pt. Marl at Aldinga, S.A. The Brown's Ck. Clay is largely obscured at Castle Cove, its apparent thinning being attributed to attenuation on the monocline. The greensand outcrops at Hamilton Ck. Castle Cove Limerstone. The Brown's Ck. Clay - Castle Cove Limestone junction is poorly exposed at the Johanna R. mouth where 30 ft. of uniform lime stone occupy the top of the section. The junction is transitional at Castle Cove The limestone is impure and of shallow water origin, and consists of about 9 Oft of alternating beds of cemented gritty lime stone and softer gritty marl. Limonite grains are abundant. Glen Aire Clay. 160 ft. of the Glen Aire Clay is exposed at the top of the Castle Cove section. The lower third consists of dark grey and brown sandy clays and sands, some of them carbonaceous, with two thin ironstone bands. The middle section is predominantly dark grey clay with intercalated beds of polyzoal limestone and marl, while the upper third is uniform dark grey clay. The Glen Aire Clay contains at least two distinct faunas, the older in the lower third showing affinities with the Upper Eocene, the younger with the Upper Oligocene and Lower Miocene. The older fauna occurs in other outcrops of the Glen Aire Clay at localities AWl, AW4 (Fig. 2) and Duck Ck. Carter (1958) and the writer differ in their interpretations of this part of the sequence. Carter identified a Z ft. limestone at the base of the middle section 'as a tongue of the Calder R. Lime stone and equated the overlying beds with clays overlying the Calder R. Limestone elsewhere. The writer maintains the Glen Aire Clay as a single stratigraphical unit, older than the Calder R. Lime stone and separated from it by an unconformity. Further work is necessary to resolve this. Calde r Rive r Lime stone. The Calder R. Limestone, at least 54 ft. thick at AW4, is a uniform bedded calcarenite with a thin discontinuous basal layer of phosphatic nodules and scattered quartz pebbles. At AW4 and Duck Ck. it overlies lower beds of the Glen Aire Clay,whereas at Hamilton Ck. it is evident that the underlying beds belong to the Brown's Ck. Clay. These observations indicate to the writer the presence of an unconformity with the implication that the whole of the continuous Glen Aire Clay antedates it. Fishing Point Marl. The Fishing Pt. Marl-between 50 and 100 ft. of clays, marls, and friable calcarenites - follows the Calder R. Limestone conformably. The poorly exposed lower part contains a microfauna equated by Carter with that in the upper part of the Glen Aire Clay and consequently included in his 'Upper Glen Aire Clay' unit. Higher up,the main shelly assemblage is distinctive, occurring elsewhere within the Gellibrand Clay and at Curlewis. Near the top of the exposed section thin limestone beds yield Lepidocyclina. An even younger horizon may be present at AW2. At this locality the thin non-marine Sentinel Rock Clay containing plants overlies it with unknown relations, and is followed with a break by Quaternary dune limestone. MooNL1GHT HEAD f PORT CANIPBELLFSEQUENCE. First examined by Wilkinson (1865) who gave an excellent section from Moonlight Head to Warrnambool, this has been described in detail by Baker (1943, 1944, 1945, 1950). Spanning the interval from Middle Paleocene to Late Miocene, it is the most complete outcropping sequence in Victoria. The beds dip gently westward off the flank of the Gtways to a point three miles northwest of Princetown where they flatten. Separate uplifts of the Tertiary occur at Ferguson's Hill, north of Princetown and at Flaxman's Hill, north-west of Peterborough (Fig. 4). Middle Paleocene marine transgression, marked by the shallow water Pebble Pt. Grit, was followed by deposition of the thick dirty marine Dilwyn Clay which locally continued until the top of the Eocene. Further we st aerated conditions obtained during the Eocene. Regression and
139 122 erosion during the Oligocene is indicated by an unconformity which dies out to the we st of Port Campbell. As elsewhere the Upper Oligocene and Miocene consists of aerated neritic limestones, marls and clays. Pebble Point Grit. Resting with slight angular unconformity on the Mesozoic, the Pebble Pt. Grit is a marginal deposit up to 80 ft. thick consisting of ferruginous quartz grit and glauconitic sandstone with minor carbonaceous gritty clays. Local lenses of polygenetic conglomerate occur near the base at Pebble Pt. From 30 ft. to 45 ft. above the base the unit is fossiliferous, containing foraminifera (McGowran, 1965), mollusca (Singleton, 1943), the nautiloids Eutrephoceras victorianum and Aturoidea distans (Teichert, 1943), the crustacean Callianassa (Glaessner, 1947), sharks' teeth and fossil wood. Inland along strike the Pebble Pt. Grit passes into non-marine clastic sediments. 6 Dilwyn Clay. The Dilwyn Clay is a ve ry thick unit of dark carbonaceous and pyritic sandy clays, extensively burrowed, and containing several thin beds of distinctive lithology. In outcrop about 500 ft. is exposed, the upper half being obscured by Quaternary dune lime stone and sands. In the Latrobe No. 1 bore, Princetown, this covered interval is represented by 500 ft. of sediment continuing the lithologies of the Dilwyn Clay. ln bores the Dilwyn Clay contains foraminife ral assemblages with abundant Haplophragmoides but due to leaching these are usually wanting in outcrop. A 20 ft. bed of glauconitic sand and clay, the Rive rnook Member, lies about 100 ft. above the base, with a Late Paleocene foraminiferal' fauna (McGowran, 1965) 'and ia' small shelly assemblage. 150 ft. higher, two lthin beds of fine-grained sandstone cemented by carbonate. - the 'Turritella' and 'Trochocyathus-Odontaspis' (Loc. AW7) bands - contain small Shelly assemblages. The se fossiliferous beds represent short periods of better aerated conditions. Baker' has distinguished the upper 100 ft. of the outcrop section as the Princetown Member on the basis of variation from the normal Dilwyn Clay lithology. Mepunga Formation and Narrawaturk Marl. Westward from Sherbrooke R. No.1 bore, equivalents of the covered interval become more aerated and fossiliferous, consisting of the Mepunga Formation, of ironshot quartz sands to sandy limestone, and the Narrawaturk Marl of clays, _fmarls and argillaceous limestone* (Bock and o1eni<l=,l 1965). These are a parallel development and equivalent in age to the interval from topmost 'U Johanna R. Sand to Glen Aire Clay in the Aire R. district. Clifton Formation. Much of the Oligocene is missing at Princetown where the Clifton Formation rests unconformably on the top of the Dilwyn Clay. Followed we stward in bores this hiatus diminishes until near Peterborough it disappears (Taylor, personal communication). The unconformity is not exposed in the outcropping section at Princetown but strongly condensed sedimentation bears witness to this period of erosion. The outcrop, some 40 ft. thick, consists of 15 ft. of limonitic gritty sandstone, a phosphatic nodule bed l-3 ft. thick, and ft. of gritty polyzoal limestone, in turn followed by the base of the Gellibrand Clay. The phosphatic nodules are embedded in a limonitic matrix in part comparable to the underlying sandstone and in part to the limestone. This bed contains a molluscan fauna, as limonitic moulds and replacements, which correlates with the basal bed at Table Cape_, Tasmania, and the very top of the Jan.Tuc 'Marl. Ge llibrand Clal. About 1, 000 ft. thick, the Gellibrand Clay is a uniform blue-grey clay with bands of con- _c retionary limestone in the upper part and contains a series of rich faunas from basal L6wer to early Middle Miocene. Gle nample Clal. The Glenample Clay, 140 ft. thick, is a blue-grey calcareous clay intermediate in character between the formations below and above. It is extensively burrowed and contains a mac rofauna characteristic of calcareous environments. A thin repetition of Gellibrand Clay
140 ~ V ` v v ` » Q 9 OI o `.I/I Q* `= o;_ ) u'o 0 $34 'II-r ::' s 'Ola :_:` 'I I':'. <I ' 9' -~ f><»f<»~~ ~.;..~. 'GQ-rf-if I.If = ; -, SMR' Rb- V3.'~ '5-1 4'. ~ :.0 ' 'f' '.» <? f : 'f 1'F.C S 4' 3 'z I '»' ~'5b. IQ,. A 1! Ml.,',:.l,._!' ;' -cd..1-e wh:» 450 :g a o o Q o 03 /» _o _'_. A ~` -., _' 'Y. _9.,.' J_v:`.(,_. `q é# o A' '» ~.?»» n 0 og; ~3~_-_'_-_.-_, ` _//7 (_ ~ ~' Jo 0 wf V' h J 3/*J*- _fr 2_ ' J_!/ 'Of'-; *_ ` ' Y 'I'*'U~.'-'~' `o ~ > 'Qi -if * r' fn =' '200-# '»`- f %-- ~~.-2 f '-'-',L- ' ' ' -=,;=1- '04- ( on. : r. ij.... Q Q <_. 0 0 l 0 I: '-_.'_.'_ ~ 'I aim' J U ~fe.st RN V1_ > _ `..f.:' a4-_~' ~?.>~~vi1z~.~:f::`:i~.=;~.~' 3 ' k f 1: _. - r ' J.~ :.~.-gf-;~.15;' - * 'i Y. i 1. ' ' ' :?9Q=1':z5;4 *F-*fit f>i;~:~'+ff=.ff' ';- L'.1:-_;.~;-,'-.I » ff. ~ -'= '»~ -'~ ~~=.s:f~-'~.f=a<>o0.~:<;-ff-xa>f»2;=:-~.-f;»s-_-=.-»; -'A', 1 0 Q 9 l.,-...,..-* y~.-~-.- _ 1 / // 15% ~ ; _.';;J/5 _~ ~`4-_~ -_ ' V Aa 96 Amzws unter iq #hx 4, ff'. ', - 0 Spa A, ' uv le :na 6* 4 _ Q/ o,p v Oo /G 0/ g gr 0, 9 / fp I. / 0 Z( 1 0* 0 QA F FA 0, 0 af), -4 0 A5,of ' 1 ' ' *Q v,. B 0/_ yn o 'oy p6 Oo F `00o_ O - Y 1 '~~.. :Jann I.'.'. -'_ Ij _._._._.. -_,.~_.-_._: Mesozo c Tf*T*RY 1 Y r sandstone. Eastern View Amaehook mudstone -Coal Measures A' ' ' S*'d % Formation T 'q *Y G' ' QUATERNARY -Dune Limestone AI luvium Fig. 3. Geological map and profile of coastline between 'Eastern View and Torquay. _ Z' g _1-X W ' _if 'X Q, v <5.L_ ', r' Q* `_ 6 ` f ~' f~ A',-. <. ` x, 'f-. _._ -- -» ' ` `- -_ /` 0.bf s' VI Q ` I 56 : 5 f ' 3' ' _f >A. C'.H E' ' - 'f I ' Ig '1 ``~ cfr S ` C /z ' Id All ; Vo ~_ ` `, urles -' -6, A-y4*~ 9 `~ :nan & __, _.ZgOJ 0.0% O _ f, _ O s 4 0./- ~~ PORT CAMPBELL _,Loo g._ -- ~ ,< <;~ _q /,J _,/ I, ` 4. /_ H ` `~ MILES o _ Q Q* A O PETQ?0ROUGH Q o -._.4/.5 Q 1 ` < A an/. Qsé use v'.f.,._,..i'1`a.»*. -:- -`.`-,.<_: I 'Tli-V -d/i - ~ f -- ' / `- Y Ig? fi) II?TI,II I bifi IpII`I7`,5SQ / _,-.. ' Sl? If'/,./Ifié If I~', _/I L' ~,_,_... I.,... ,-..,'y.. L/ J'..~»<,.»r,..,>.. '.'. ;.Co. H tbob ..... _.._ ,_,< _*T-_.,/2 _,`..v. -.Q Q;,` '} _ _,. ) '; 1_.;,-_'T,.,...,.f:..'». k ~ 'T 0 H - /.1.,<~~ ~ J /_F. '-, jf'» ' II;iQ_J QQ: 1,3 :;L:,';. > L_. ;_? .`.. 0`:,Ir gf. 'i2, ;,-'Ge j}~;i j` éi I`T.`I; I` 5.}'I<I` '_'-_ 'TI s ` 1; X I' kr _»- ' rg. ;,-*.`-...~.' -_QL.3/1'-~;` J' % I',I G/ '- ~,» 3 3,095 Q,.9 A 4* 4 '_ 00 _ f _,;', _ `_.-_`.`;,.,;..`(..,f; f/_ aw/ h. ' vwwe ' / 'P ' 4/V6 ' ' I'-' ' `I e 9 o» _ 1 ~ :ff ' ~'~ '~~ - 4 T T' 4 e.~ M/, 9 6 '~' v '` O Q -`~~.. >&9 5 % * 0' 6/'-' 9 '28 //_ 06 '> 0 AF 6; T I PR' ET WN`1... `*' - Q' Q90 ' FEZ1-1-' >''' W ' -_/T/3. L `:i } :~;f'/ar' ' I';'`' 21 'I -- =v - - i `;.,'2 0~ ' LLQZL- ' - ` ` - ` - ~/LITI;_,»?'I'I`S'>I 'f-ff fti:_1-;;i:f;-:_: ;?'3` l 1 ', ~ I, `,. *_ ~ _ `.,.».._..»... Q.... ' _~' 0 A90 9a 5 0 if) v - L) _,-.,.;_,`..,..._....»....W 6, f &» er 500 %% <<< <<< ' Mesozouc PALEOCENE-Eocene OLIGOCENE-MIOCENE QUATERNARY Sand. cla marl Ff L;F;;?:`L 'd t ' '- limestoni 0 L;mestone. ma;l Dune Limestone.Sand AI luvium MILES Fig. 4. Geological map an d pro f 1' 1 e o f coastline between Moonlight Head and Peterborough.
141 124 facies occurs 30 ft. above the base. Port Campbell Lime stone. The ft. of Port Campbell Limestone grades up from' alternating limestones and calcareous clays inthe lower part into pure limestone. The limestones are cream, friable calcilutites containing secondarily cemented concretionary bands. They weredeposited under extremely quiet off- shore neritic conditions as shown by preservation of the crab Ommatocarcinus gorioensis complete in all details. These limestones are not pelagic as claimed by Bock and Glenie (1965), but represent bioclastic lime mud washed in from shallower water. Lenticular clays and marls in the lower part at Rutledge's Ck. (AWl0) yield a molluscan fauna noteworthy for the coexistence of Eotrigonia and Neotrigonia acuticostata. This late Miocene fauna is also found at Lake Bullenmerri, Camperdown and at Lake Keilambete. The limestone fauna is characterised by the echinoids Eupatagus laubei and Schizaster siphenoides, with Lovenia woodsi common towards the top. Two thin bands with the calcareous worm tube Ditrupa form useful markers traceable for many miles in the cliffs. NEWER VOLCANICS. The Western District plains are cove red by a sheet of Pliocene to Recent olivine basalt flows. The older flows are weathered and soil-covered whereas the youngest flows retain rough blocky surfaces known as stony rises. Pyroclastics are largely restricted to the volcanic cones but are wide spread in the Colac and Camperdown districts. The numerous small volcanoes include lava cones, scoria cones and maars, with a few composite types such at Mt. Porndon. The younger volcanoes are excellently preserved with craters, spatter cones, etc. and show a marked concentration towards the southern edge of the lava field. The physiography of these volcanoes and lava field has been described by Ollier and Joyce (1964) and reference should be made to Chapter_ l2..~ The lavas are predominantly olivine-labradorite basalts with some limburgitic basalts in the Camperdown district. The pyroclastics contain ejected blocks and shaped volcanic bombs, the latter frequently with olivine-diopside cores. Alkali feldspar crystals are common in some of the scoria cones. QUATERNARY. Plio-Pleistocene outwash sands produced during uplift of the Otway Ranges are a feature of lower areas on the flanks. On the Johanna R. for example poorly sorted brown clayey sands cover the Tertiary at the foot of the rnonocline. Many such occurrences cannot be dated and are difficult to distinguish from older Tertiary non-marine sediments. Quaternary dune lime stones up to 300 ft. thick have built up at suitable sites along the coastline. These are usually capped by fixed sand' dunes from which sand sheets have been blown inland, as at Cape Otway. Currey (1964) has recognised the existence between Mt. Emu Creek and the Barwon River of a vast post-newer Volcanic lake of which L. Corangamite and L. Colac are the two large st remnants. Associated with this lake are lacustrine sediments and a complex se ries of lunettes, some of which are composed of the gasteropod Coxiella. The planated Port Campbell Limestone is covered by up to 20 ft. of residual clays. Several inches above the overlying buckshot gravel horizon and some nine inches below surface is the location for the beautifully preserved australites made world famous by the researches of Dr. G. Baker. PH YSIQGRAPH Y. The Otway Range s,though deeply and intricately dis sected,still show the form of the pre- Tertiary surface. Structures associated with their late Cainozoic uplift are still evident topographically and the valleys of the main streams are in large measure structurally controlled The coastal streams, constantly rejuvenated by coastal erosion contain numerous waterfalls. Landslipping is commonplace on the steep slopes. Tertiary rocks in the flanking regions were planated and lateritised at some time in the Pliocene, following which uplift and dissection to several hundred feet has occurred. This
142 125' uplift may be equated with late movement on structures such as the Barrabool Fault which have deformed Newer Volcanic flows. The coastline, one of spectacular scenery, is mainly backed by cliffs, locally up to 500 ft. high, and shows considerable contrast between the Mesozoic with extensive shore platforms, the various Tertiary formations a.nd th Pleistocene dune limestone. The cliffs on either side of Port Campbell cut in the flat-lying Port Campbell Limestone areparticularly noteworthy, with gorges eroded along major joints, caves and rock stacks - see Chapter 12. ITINERARY IN TRANSIT. FIRST DAY Melbourne to Geelong: Werribee Plains - Newer Volcanics on marine Tertiary and brown coal. Werribee R. (20 m.) - post-basaltic alluvium with marsupial remains. Pass You Yangs (1,154 ft.) (30 m.) - granite promontory in Tertiary sea. Hovell Ck. (35 m.) - Quaternary fresh-water limestone and clay. Approach Geelong (45m.) - Pleistocene postbasalt Lovelybanks monocline on right. Geelong - view of Corio Bay with Bellarine Peninsula on south. Geelong-Torquay: Barwon R. (46 m.) - Barrabool Hills uplift on right. LOCALLITY l -_M_t. Quneed (55m. Quarry in Newer Volcanic agglome rate containing blocks of baked Tertiary clay and calcined limestone. ViewfE. across L. Connewarre depression to Bellarine Peninsula uplift. Torquay (62 m. Coastal sections between Torquay and Angle sea (72.m. Return to Geelong (85 m. LQCALITY - Jan Juc Pt., Zeally Lime stone. _LQCJALITY 3 Torquay: - Jan.Tuc Ck. mouth to B_ird Rock. Cellepora Beds - Puebla Clay - Jan Juc Marl arched on Bird Rock structure. LOCALITX 4 - Bird Rock to Fisherrnanfs Steps. Jan Juc Marl in centre of Bird Rock structure ove rlain by Puebla Clay. shelly glauconitic marls and intermediate calcareous clay facies.,locality 5 - Fisherman's Steps to Rocky Pt. Transition between Inte rtonguing transition between.tan Juc Marl through calcareous clays into calcarenites of Pt. Addis Limestone. LOCALITY 6 ->FBell's Headland. Dark Anglesea Sand - marine clays of Angahook Formation - basal tongue of Jan Juc Marl - Pt. Addis Limestone - Puebla Clay. LocAL1TY 7 - Pt. Addis. Angle sea Sand - Angahook Formation, non-marine sandy clays, littoral sands intertonguing with base of Pt. Addis Limestone. SECOND DAY LCCALITY 8 - Anglesea Brown Coal Mine. Thick lenticular brown coal seam overlain by sand, clays of Eastern View Coal Measures - Angle sea Sand forming walls of valley.
143 126 LQCAILITY 9 - Soapy Rocks, Angle_ ea. Angle sea Sand - non-marine Angahook Formation (see text) - Quaternary dune limestone of Pt. Roadknight. Follow strike section to Urquhart's Bluff (35 m.) in Angahook pyroclastics. Airey's Inlet (37 m. LOCALITY 10,g;_i~e_y's Inlet. Agglome rates and bentonitic clay of Angahook Formation - unconformity to Pt. Addis Limestone with basal sands. LOCALITY ll - Split Rock, Airey s Inlet. Basalt of Airey's Inlet volcano overlain unconformably by Pt. Addis Limestone. IN TRANSIT. Airey's Inlet to Eastern View: Angahook non-marine sazéids from Airey s R. to Fairhaven (38m.) - Anglesea Sand to Mogg's Ck. (39%m.), dip 30 SSE. - Eastern View Coal Measures to Eastern View (41 ni.) - Mesozoic. Eastern View to Lorne: Grassy Ck. (42.m.) - steep dips up to 60 in Mesozoic - view of Tertiary sequence to Airey's Inlet. Big Hill (325 ft.). Descend to Lorne (49 rn.) - SE. dips decreasing into Lorne syncline forming Loutit Bay. Lorne to Apollo Bay: Pt. Grey (50 m.) - S. flank of Lorne syncline. George R. (51 rn.) - anticline. Cumberland R. (54m.) alternating units of sandstone, mudstone in shallow syncline. Mt. Defiance (55 m.) - sharp anticline with 700 dip on SE flank - steep cliffs. Wye R. (6Om.) to Kennett R. (63 m.) - gentle SE. dips. Pt. Hawdon and C. Patton (67 m.) - syncline - early Tertiary marine sands at 500 ft. C. Patton to Apollo Bay (78 m.) gentle S. dips to Apollo Bay syncline with offshore outcrop of Brown s Ck. Clay. LOCALITY l2.- Skene's Ck. Major S. IN TRANSIT._ Monocline (83 rn. Q facing monocline in shales, sandstones, with thin coal seams - minor faults,etc Skene's Ck. to Cola-ic: Mt. Sabine (1,911 ft.) (93 rn.) - crest of main range. Barramunga (99 rn.) - major N. facing monocline. Forrest (103m.) - edge of Tertiaries. Colas (124 m. ). THIRD DAY IN TRANSIT. Colac to Hordern Vale: Kawarren (l3m.) - U. Oligocene limestone similar to Pt. Addis Limestone. Gellibrand (l7m.) - early Tertiary coal measures. Ascend main range to Beech Forest (28 rn. ). Cross Aire R. (31 m. ) to 'Cape Horn (40 rn.) and Hordern Vale (47m. _LOC,AI;._I_Tgg}_f_1_ _ fp Hordern Vale. Calder R. Lime stone. Fishing Point. Fishing Point Marl. ;_l_og.»,.l_;_'g 14 LgOCALI T_ _{ 1 -I Hamilton Ck. Brown s Ck. Clay at foot of Castle Cove Fault. LGCALITY 16; - Spud P_gin t. Calder R. Limestone. LOCALITY 17 - Castle Coye (AW5_)_,g Glen( Aire (_ 3g1' 1. Castle Cove Fault and monocline - Johanna R. Sand - Brown s Ck. Clay - Castle Cove Limestone - Glen Aire Clay. _
144 LOCAl.»_IT_l 18 - Johanna R. coastal section (64m. V Rotten Pt. Sand - Johanna R. Sand - Brown Ck. Clay - Castle Cove Limestone - Johanna R. monocline - View of coastline W. to Pt. Reginald. Johanna R. to Laver's Hill (72m. Follow main ridge to Ferguson (81m. Gellibrand (93 m.). Colac (110 m.). FOURTH DAY IN TRANS IT. Colac to Gellibrand (13m. Follow Gellibrand R. valley in early Tertiary non-marine sediments to L. Gellibrand (41 m. Detour to LOCALITY 19 - Pebble Pt. Mesozoic - unconformity to Pebble Pt. Grit - Dilwyn Clay. Return to L. Gellibrand and Princetown (49 m. LOCALITY 20 - Coasta_1_ ecj:ion SF. cgfrincetown. Pebble Pt. Grit - Dilwyn Clay including Rivernook Mem., Turritella and Trochocyathus Beds, and Princetown Member. LOCA_L_ITY 21 - Princpetown. Clifton Formation - Pleistocene dune limestone. Princetown to Port Campbell (61 m. LCCALITY 22 - Coastal Section from Glenam p1e Steps to Sherbrooke _R. Gellibrand Clay - Glenample Clay - Port Campbell Lime stone - coastal scenery. LQCALITY 23 - Rutled_ge's_Ck. m. Fossiliferous clay, marl near base of Port Campbell lime stone. Coastal scenery to Port Campbell. Port Campbell to Cobden (85 m.) - Tertiary sediments. Cobden to Camperdown (93 m.) - Newer Volcanics. FIFTH DAY LOCALITY 24 - Coastal sectionsfrom Port Campbell to Peterborough (41m. Port Campbell Limestone and coastal scenery. Peterborough to Timboon (52 m. ), Cobden (67 m. Camperdown (75m. LOCALITY 25 - Lake Bul1enme_1;_ri, Camperdown. U. Miocene clays in L. Bullenmerri, L. Gnotuk maars. LOCALITY 26 - Mt. Leura. Nested maar - quarry in volcanic ash with olivine bombs. Camperdown to Colac: Pomborneit (86 - stony rises, Mt. Porndon on right. Pirron Yallock (92 m.) - L. Corangamite on left. Colac (104m.) - L. Colac. Colac through Winchelsea (127 m. ), Geelong (150 to Melbourne (195m. Baker Baker Baker Baker Bock,G,G,G,G 7 S 'D Q P.E REFERENCES Eocene Deposits South-east of Princetown, Victoria. Proc.Roy.Soc.Vic., 55: The Geology of _the Port Campbell District. 113;, 56: Phosphate Deposit near Princetown, Victoria. J0ur.Sed.Pet., 15: Geology and Physiography of the Moonlight Head District, Victoria. Proc. Roy.Soc.Vic., 60 : and Glenie, R.C., Late Cretaceous and Tertiary Depositional Cycles in South-Western Victoria., 79 :
145 T -- _ 5',_: 128 Carter, A.N., Tertiary Forarninifera from the Aire District, Victoria. Bull. Geol. grv.v&., 55; Carter, A.N., Pelagic Forarninifera in the Tertiary of Victoria. Geol. Mag : Currey, D. T., The Former Extent of Lake Corangamite. Proe.Roy.Soc._Vic., 77: Dettrnann, M.E., Upper Mesozoic Microfloras from South-eastern Australia. 77 : Edwards, A. B., Notes on the Geology of the Lorne District, Victoria. Ibid., 75 : Glaessner, M.F., Decapod Crustacea (Callianassidae) from the Eocene of Victoria., 59 : 1-7. Glaessner, M.F., An Ammonite from the Upper Cretaceous of Victoria. _1_1_;i d_., 77 : Kenley, P.R., The Occurrence of Marine Cretaceous Sediments in the Belfast No.4 Bore, Port Fairy. Min.Geo1.Journ.. 6 : Leslie, R. B., Petroleum Exploration inthe Otway Basin. 8th Cornm.Min.I/Ist. Congr. Proc., 5 - Petroleum; McGowran, B., Two Paleocene Foraminiferal Faunas from the Wangerrip Group, Pebble Pt. Coastal Section. Western Victoria. Proc.qRoy.Soc.Vic_., Ollier, C.D. and Joyce, E. B., Volcanic Physiography of the Western Plains of Victoria., 77 : Parr, W. J., An Australian Record of the Foraminife ral Genus Hantkenina., Raggatt. H.G. and Crespin, I., Stratigraphy of Tertiary Rocks between Torquay and Eastern View, Victoria. 67 : Singleton, F.A., An Eocene Molluscan Fauna from Victoria., 55 : Taylor, D. J., Forarninifera and the Stratigraphy of the Western Victorian Cretaceous Sediments., 77 : Taylor, D.J., Preservation. Corrmpositirm. and Sigrlifisance of Lower Tertiary 'Cyc1arnmina Faunas.. 78 : Teichert, C., Eocene Nautiloids from Victoria Wopiner, I-I. and Douglas, J. G. (Editors) The Otway Basin of Southeastern Australia.J.=..._.._.. s, S _991.Sv v9 S._..._S9s*h A»9.e 2..r3l1a.99.9 V..., W.9» 464 PP- QF :su Hs ;_ ocgne ERA -BVI. ii '.».l.l ;<, 'i*#- -~;1 -_ 9 _#Q Ants 01HDlC ig%}_ 4. _ ra-=' _.ia,.--*'.;-_''- -a *_* - t :ny `% ~ ' - Q _Mun i 6.L '_` t?!_i:!.yt; ;_'j _--I; ` - _,._,..-~._. A~: ;;T:'S.Te A it' ~ asa i_- 'w; f CA na on/ac so ug; in ctr.: 9.. f.,1_;;=.-?;;?i=-=- Q ' ` 7 _'7f_~ :»- --'1f:;'f-Z* - 'V ':?_` `;`--- *'?-'1'-1_f;.7f, ';f': _ * ' _*Tin I 7 if* T _ A'--..r f 7 Ear '1' ' '_ is sf; if; %_ Q<3_ _,~,;,'_,.-f>* ii ~-._-4. _gg A -; `f'i;-sl-=... L.,_` af 3'=;'=- '* ' '., pgggggf ; ; v L r;;;: ;.; ;_;.;;:: ; -7 'ff f A `-_i--_ ;.;5- ai _-i»;;1::' f-t,'qi -=A&` L =, B ~.=fi..~~-f B ' ' I: ~._--'J5* ~- i isa- _ f-»{<f;.-:é` /53; 'lu 11, ~-E7_`-'*' f'; '; =9- --:ip 5.) ` *m 'fi 'X _' ~~_. - ' I- - T Q The Otwag I/sliand in Tefitécmy times. F.M.I<fLau.5e - Pfwg. Rep. Geoii, Su/Lv. l/le., 1874.
146 CHAPTER GEOLOGY OF SOUTH GIPPSLAND by O. P. Singleton INTRODUCTION. The South Gippsland region illustrates extremely well the Mesozoic and Cainozoic tectonic bel-t which stretches across southern Victoria out on to the continental -shelf. Its position has been determined by a crustal weakness across the base of the Tasmania 'peninsula. The pre sent Bass Strait is a distinct structural entity inherited from the Bass Basin and seems to have become an open seaway only in the Oligocene. PALAE OZ OIC. Palaeozoic rocks outcrop along the southern margin of the South Gippsland Mesozoic trough from Phillip Island to Toora as intermittent inlie rs. In addition small inliers occur within the trough at Turton's Creek and Boolarra. The major structure of the Palaeozoic is clearly complex but is not sufficiently exposed to permit correlation with the major structures in the main Palaeozoic region to the north (Thomas, 1939). The most important structure is the Waratah Bay axis, with a core of greenstones, which is described in detail below. Its western boundary, The Bluff -.Point Grinder or Walkerville Fault Fl (Fig. 1), separates the axis from a narrow belt occupied by the Lower Devonian clastics of the Liptrap Formation. Further west late Upper Ordovician sediments in the Bald Hills show the presence of another positive structure about which no details are known. North-east along the trend of the Liptrap Formation the little-known Hoddle Range consists of Silurian -Devonian flanked on the we st by Upper Ordovician. Further north Lower Devonian occurs in the Turton's Creek inlier, while the inlier of graptolite-bearing Lancefieldian at Boolarra might belong to the same positive structure as the Bald Hills. The presumedlate Devonian granite of Wilson's Promontory is the northernmost of a series of granitic outcrops trending south-east across Bass Strait to Flinders Island-. GEOLOGY OF THE WARATAH BAY AREA. The Waratah Bay area was first mapped by Ferguson (1928) and its geology has been described by Lindner (1953) after more detailed mapping of the coastal sections. The Palaeozoic rocks are unfortunately largely masked by a veneer of Cainozoic sediments except along the coastline,where they are excellently exposed in cliffs and on shore platforms. The coastal exposures show a partial cross-section of the Waratah Bay axis, which is typical of the structural axes crossing Victoria at intervals and illustrate the structure better than most. Its western boundary against the Liptrap Formation is the steeply we st-dipping fault Fl with its associated wide shear zone. The axial core consists of thick greenstones believed to be Cambrian in age. Faulted by FZ against and to the east of the outcropping greenstones is a slice of the Lower Ordovician (Tremadocian) Digger Island Lime stone. Re sting unconformably upon the greenstones,between Walkerville and Bird Rock and at Point Grinder are exposures of the Lower Devonian Waratah Limestone; To the east of the Digger Island Limestone, and faulted by F3 against it,is Waratah Lime stone,ove rlain unconformably by the late Lower Devonian Bell Point Limestone. The eastern flank of the Waratah Bay axis lies beneath Waratah Bay. An ae romagnetic survey by the Bureau of Mineral Resources has traced the axis for some 30 miles out into Bass Strait where it swings to a N-S trend before being blanketed by Bass Basin sediments. This survey also indicated a duplication of the axis further east, beneath Waratah Bay and Corner Inlet. Evidence for the persistently but intermittently positive nature of the Waratah Bay axis is afforded by the presence on it of ne ritic Lower Ordovician, in contrast to the otherwise entirely bathyal sediments of this age; of the neritic Lower Devonian Waratah and Bell Point Lime stones each following an unconformity; and the occurrence in the flanking Lower Devonian Liptrap
147 130 Formation of detritus from the greenstone suite and of boulders and fossils from the Waratah Limestone (Singleton, 1965). Cambrian Greenstones. The greenstones are comparable in all respects to those forming the cores of other axes and known to be Cambrian in age. They are a very thick pile of altered intermediate to basic lavas with intercalated tuffs and some agglomerates. Lenses of chert and shale, from which Lindner recorded sponge spicules, and veins of jasper,occur in minor amounts, with lenses of dark recrystallised unfossiliferous limestone close to fault FZ. The greenstones show less alteration than is usual in these axes probably because resistant lavas greatly predominate. Lindner recorded ropy flow surfaces locally, and structures resembling pillows. The lavas are fine grained, with granular augite and albitised plagioclase in interstitial serpentinous material. Serpentine pseudomorphs after olivine are also recorded. Occasional doleritic rocks may represent dykes. Lower Ordovician - Digger Island Limestone. The Digger Island Limestone occupies a narrow fault slice between faults FZ and F3. Dips are steep easterly, flattening locally at Digger Island, and close to the bounding faults shearing is intense. Lindner estimated the thickness at about 120 ft. The lower portion consists of massive recrystallised grey limestone which has yielded a single indeterminate nautiloid only. This is succeeded by brown decalcified mudstones containing a trilobite fauna belonging to the Kainella- Leiostegium zone of Tremadocian (Lancefieldian) age, together with some brachiopods, cystid plates, hyolithids, tentaculitids, and rare nautiloids. The upper beds are shales and muddy lime stones with orthid brachiopods. The trilobites include species of Geragnostus, Leiostegium, Protopliomerops, a Kainellid, an unusual Pliomerid, and the earliest true Harpid, while the brachiopods are an abundant small Orthid and Fi 1; _elnburgia. Lower Devonian - Waratah Limestone. The Waratah Limestone outcrops at Walkerville between The Bluff and Bird Rock, and at Bell Point and Point Grinder. Three lithological units were recognised by Lindner at Walkerville, which were formalised by Teichert (1954). It rests unconformably upon greenstones at Bird Rock and at Point Grinder where the contact is better exposed (Thomas and Singleton, 1956). The fossil lists Cited below have been kindly provided by Dr. J. A. Talent. In the Bird Rock-The Bluff section, the béwal Bird Rosk member consists of well-bedded grey dolomite overlain by brown muddy limestone containing fragments of chert. Scouring is evident on bedding planes. A micaceous mudstone on the road above Walkerville probably fits in here The fauna is notable for the variety of tabulate corals and includes _Ehillipsistraea rnaculosg, I-Iexagonaria approximans, Lyrielasma? subcaespitosa, Spongophyllum _serratuml Tryplasma wellingtoliense, _Favo goldfussi, _F_:_? ovatiporus, Thamnopora a_ng_usta, _Trachypora sp.,? Striatopora sp., Heliolites daintree_i, _Aulopora_ cf. conglomerati, Syringopora flaccida, stromatoporoids, brachiopods including chucherte11a, Sphaerirh_ynchia and Howellella, lamellibranchs, gasteropods including Bellerophon and Coelocaulus, and occasional nautiloids. This is followed by the Kiln member, generally a light grey rock varying from well-bedded to massive. It is relatively deficient in fossils which include? Ps eudamplexus sp., Lyrielasma? subcaespitosa, Favosites goldussi, Alveolites? stamineus, Heliolites, stromatoporoids, and Loxonema. Equivalents of The Bluff and Kiln members occur at Point Grinder and Bell Point. At Point Grinder a basal grit containing che rt fragments and tabulate coral colonies abuts against the greenstones and is followed successively by 20 ft. of grey dirty limestone and about 400 ft. of bedded white limestone similar to the Kiln member. Fossils are scarce. At Bell Point about 140 ft. of bedded to massive light grey limestone contains at the top a biostromal bed with stroma- 'toporoid and tabulate coral colonies. Atrypa occurs lower in the section. The upper Bluff member at Walkerville, at least 260 ft. thick, is a thick-bedded dark grey lime stone containing a fauna dominated by Amphipora. In addition it contains I-Iexagonia aff. approximans, Acanthophyllum, Favositges, Thamnopora, Heliolites, and Syringopora flaccida. The faunas of the Bird Rock and Kiln members are closely related and compare with those in the limestone lenses of the basal beds of the Walhalla Group, which Talent considers to be late
148 I 131 / Y W//V 7 I V?'`1` A/ ALD HILLS /Ax , J QUATERNARY /'I ` ' 1 1 ` `, '. i I g F( ` 200~ I ` _ _; I 1 W ` U) ' TERTIARY % ` _ - Q- MEsozoIc 0 Q LOWER DEVONIAN I 1 'IZ' - -; BELL POINT LIMIESTONE /,/ X / ' /]' 7 ,f O /, WARATAH.LIMESIONE 'Q-J ` (3 'I-' I 'J Q ' % <1 /` 00~~' 'f ` /1 ~~ ~, f >_/~ LIPTRAP FORMATION 1 ) (J' ) ( 1 `/ ` - f ' if < ' R »~* Q J I/ T ~_ UPPER ORDOVICIAN I, _ - _A '_ / ` f ww S% S# f;» ' ' Umm 5 _ 00) Q 3 I DIGGER ISLAND LIMESTQNE < ) 1' 9 (' /`.ji O CAMQBRIAN GREENSTONES ` T `. q Q ) X NR&~' SERFENTINISED GABBRO ` ,` Yu-11 > >' 'T_a g 1 2 c) 1' L1 f,' L _ MILES K1 i' ~ WARATAH BAY *ENN,JP-. to , 9 F2 / /r Y ' ` e' ; L _ Q' Fl ` ' ` f ~ `~ DIGG > Q- -' -1 / ll,:,.{:.» 5, ',;.'/. I 'M 3`cZ5I I. : ~» BIRD Roc1< I-' '=*; 1 ~lalkerv1lle»'.. 1, ; .`. _'_- :».::-._`-'Et'-.,.. _{ Wi THE BLUFF ER I. _- 2; >. f_f-. '~- _' DIGGER I. H. ` 1 F3 '.`~-' %<»f~' ~ 'Z '1 -.'»?.-_~.-/,_~- I, ` '. _ _.-.'~ I' : PT. 0 ) F3 - ; ' MU f' fa 'wo SHROOM E F2 I ROCK 5 IM 'pr gag Q W Lf: I I g $ '` 4.` '».' $ v. 'og l' V ; of Fl FT. GRINDER Q <94 '62 ' if F2 IFB 6* r Og/ 4.bwg 02, 5, 18 CAPE LIFTRAF 2* Fig. 1. Geological map of the Cape Liptrap Peninsula, (after Ferguson, 1928, and Lindner, 1953).
149 132 Siegenian in age. The Bluff member is slightly younger but equivalent lime stones are unknown elsewhere in Victoria. Lower Devonian - Bell Point Lirrre stone. In erecting the Bell Point Lime stone Lindner included the units comprising the Waratah Limestone. I-Ie did not distinguish between The Bluff member and the younger Bell Point Limestone as now restricted by Talent (1965). The latter outcrops only between Digger Island and Bell Point, on the eastern side of the Digger Island Limestone and separated from it by fault F3. At Gair Rock on Bell Point it overlies the Waratah Limestone with a slight angular unconformity (Talent, 1965). The contact shows erosion of the underlying beds and incorporation of limestone boulders in the basal beds of the Bell Point Limestone. This unit consists of wellbedded dark grey muddy lime stones inte rbedded with some lighter grey lime stones and black shales. Lindner estimated a thickness of at least 140 ft. The Bell Point~Lime stone is richly fossiliferous with a tendency for the fauna to be banded. Individual beds tend to be rich in gasteropods, brachiopods, or corals and there is a prominent biostromal horizon with _Qhalcidophyllur_13_, tabulate corals, and stromatoporoids. At and about this horizon are black shales with an ostracod assemblage described by Krommelbein (1954). Included in the fauna are Hexagonaria stevensi, _I-I ; aff. approximans, Dis_phyllum?goldfussi, Chalcidophyllurn camp_anenf_e and var. nanu;_m, C. disco_rd, Tryplasma murrayi, Favositgg goldfussi, _l:_. aff. bryani, Aulopora cf. conglomerata, Syringopora flaccida, stromatoporoids including Stromatopora concentrica, Spinella buchanensis Buchanathyris waratahensis, _1_3_. we stoni, lamellibranchs, and gasteropods including a new Trochid, Amphelissa isisensis and Tropidodiscus. The brachiopods are closely comparable to those in the Buchan Caves Limestone which Talent places in the late Emsian. Other elements are largely specific to the Bird Rock Limestone.~ Lower Devonian - Liptrap Formation. The Liptrap Formation, occurring west of boundary fault Fl, represents deposition in somewhat deeper water on the flank of the Waratah Bay axis. Some thousands of feet are exposed but without stratigraphical relations to any other unit. It consists of dark grey mudstones and shales with bands of sandstone interbedded rhythmically, and sporadic massive units of gritty and pebbly sandstone. The sandstone bands vary in thickness from several feet down to thin laminae, the spacing between them increasing with the thickness of the bands. They show fine current bedding. The thick sandstone units are more massively bedded and contain siliceous pebbles and gravel some of which were derived from the greenstone suite. Occasional slump conglomerates with pebbles of chert, jasper, and greenstone, contain in addition boulders of lime stone considered by Talent to originate from the Waratah Lime stone. Except for psilophytalean plant remains at Livingstone Creek no undoubtedly autochthonous fossils are known. Worn tabulate coral colonies occur in the massive sandstone units and all species are compatible with derivation from the Waratah Limestone. These are Phillipsastraea maculosa, H~eliophy_llum pin_guiseptatu_m, Favosiies goldfussi, F_;, sguamuliferus nitidus, Heliolites daintreei, and rare brachiopods. Lithologically the Liptrap Formation compares closely with the Walhalla Group and Talent places it in the Emsian, equivalent to the break between the Waratah and Bell Point Limestones. However the same lithological association with sandstones containing fragments of chert, greenstone, and phyllite occurs in the Turton s Creek inlier and with Monograptus belonging to the group now regarded as early Lower Devonian. This indicates that this phase of clastic deposition was already operative earlier_and implies overlap in time with the Waratah Limestone. Se rpentinised Gabbro. Small pods of serpentinised gabbro intrude the greenstones and Digger Island Limestone along the line of fault FZ and may be the source of osmiridium found in the recent beach sands. The Limestone has been altered for 80 ft. from the contact and Lindner has recorded ve suvianite and brucite from the metamorphosed rock.
150 *F a, A M ` ` w 5 ig ` W ' A :;-_1-_'.; ~} + <~<~ %»» ff:ff if ' <z> NA A If A -_ -_- ' - W _. ' j_ T_ 3'~ _ -/-< utroner-»t»a;~2m~fxs ~»1;r»_ 1- ~ <9 '~» < '. *. #;~.;»_ ~ _ 1 fr: v, ' 1.-,; 0RwELL -..._ - y ~* 7 Ay3$ l`s Eg k`&i Fl? N, M,RBo6_N0RTH- /l _ QQ* Q `QY!Y` - ~» Q, ~ - /', B/u_oo»< ; ~ ' an N I as Y Y; ` Y /M r _ i` 1. S* ~~ 1 if 1 W i, Q vs },> -1 1 ij* A AA / QF. V _:_.&:$_,9..._Q'. :.' _ W /' ' ._'` f = `&w$} %``bf ` gs 4/ KORLJMBURRA ~ 9,J' A * A 9 A A A ) & i t ``,;vket r ; * `f *Q.--' -' J / ia a QE a t, ;; ` _ o a;;=,<= a,a»f~» it, ~.. `M`_` fr Guam f ~ Q: CAPE `. %Kg, Pnrenson SOQS < SS & FAU _,~ ` ' T we_shpool Q? 5>,> % `-6 C * 133 'z '_ Q /» & t g {p 6 02'/ < ZS/ cormsn INLET SNAKE ` ~~ A Q ' -I- 64.s;, S WARATAH an 0 + '794/r cus L PTRAP ' 'I' + 'l' + + +Mt.l;trobe 2475 N 9 ' ',:. + WH-SON S PRoMoNToRY Sadglly Lg te. Qumannmv TeR'r ARv? DEVON AN Fldptth TERTIARY MESOZOIC S _UR0_DEy0N AN dltne, 5Tdtt h, 0,O 20 onnovncsm Ll Males Sh' d t Fig. 2. Geological map of South Gippsland (based on Geological Survey of Victoria l:250,000 Warragul map sheet).
151 134 The gabbro varies markedly from medium to very coarse grained in texture and also in original composition, consisting of varying proportions of serpentinised pyroxene and olivine and altered plagioclase with interstitial and vein serpentine. Opal, calcite, and limonite veins are also present. The age of this gabbro is not known but the absence of strong shearing suggests that it was a relatively late event. Tertiary of Warat_ah Bay Area. Non-marine Tertiary conglomerates and sands up to 100 ft. thick cap the Palaeozoic on the shelf between Walkerville and Point Grinder. Granitic quartz, probably derived from the Wilson's Promontory granite, is abundant. Evidence of faulting of these beds is seen near The Bluff, suggesting late Cainozoic movement on the main boundary fault Fl. MESCZOIC - STRZELECKI or KORUMBURRA GROUP. The Mesozoic sediments of South Gippsland were deposited in an E~W trough which geophysical surveys have shown continues eastward across the Gippsland Shelf. This trough is closed on the south by the Palaeozoic inliers referred to above and is blocked on the west by the Mornington Peninsula. Its configuration is not known in detail but is likely to be affected by basement structures along the NE-SW Palaeozoic trend. Mesozoic sediments are not confined to the trough but are also preserved on its apron as at Tyers River and Fish Creek. Within the trough deposition was extremely rapid, 9000 ft. of sediment having been proved in a bore east of the Balook Block without reaching bottom. It is evident from the structure of this block that the maximum thickness is considerably greater. The sequence is extremely uniform with a monotonous alternation of feldspathic sandstones, mudstones and shales. This uniformity has prevented detailed stratigraphical subdivision and mapping. The petrology of the suite was described by Edwards and Baker (1943). The greenish-grey sandstones, approximating to arkese in composition, are fine-grained lenticular units showing conspicuous cross-bedding. They consist of 10-15% of quartz and Z5-35% of feldspar (oligoclase and orthoclase with minor amounts of pe rthite and microcline) set in a chloritic cement. Minor constituents include chloritised and bleached biotite, occasional hornblende, and rare augite grains. Scattered through the sandstones are subangular to rounded grains of ande sitic rock with andesine and chloritised ferromagneaians in a base of plagioclase rnicrolites and, or glass. Besides chlorite, cementing materials include zoisite, epidote, calcite, and albite or zeolite. Calcareous cannon-ball concretions are a conspicuous feature in these sandstones. The finegrained rocks range from sandy mudstone with angular fragments of quartz and some feldspar, to clay shale s. The sandstones frequently contain mudstone pellets and coalified wood fragments. Autochthonous lenticular conglomerates are scattered through the sequence, with mudstone pebbles from contemporaneous scouring set in a sandy matrix. Near the base of the sequence conglomerates with exotic pebbles are associated with grits and sandstones. Bituminous coal seams, averaging 2-3 ft. but up to 9 ft. in thickness, were mined at Wonthaggi, and with smaller production at Outtrim, Jumbunna and Korumburra. The restriction of workable coals to this we stern end of the trough suggests more stable conditions here during part of the depositional period. Plant remains are common particularly in the mudstones. This flora, monographed by J. Douglas (1969), consists of ferns, pteridosperms, bennettitaleans ginkgoaleans, conifers, and a few angiospe rms. He recognised several floral assemblages within the Gippsland sequence. In describing the microflora Dettmann (1963) recognized three microfloral assemblages (Stylosus, Speciosus and Paradoxa) which she considered to span the interval from post- Kimmeridgian at least to the Albian. On this basis a Lower Cretaceous age is at present favoured for this Mesozoic. For unknown reasons microfloral remains are virtually absent in outcrop samples.` With the exception of one locality other fossils are extremely rare being limited to occasional Unio, fish and a reptilian claw. However the locality at Koonwarra, described below, has yielded a very rich flora and aquatic fauna which has given an excellent concept of the life and ecology ofa Mesozoic lake (Waldman, 1971).
152 135 The outc ropping Mesozoic was apparently deposited under non-marine fluviatile conditions. All evidence points to accumulation on a rapidly subsiding flood plain carring ephemeral lakes and coal swamps. Under such conditions braided streams give rise to sheet sandstones, a feature unlikely under lacustrine conditions. Attempts to invoke a marine environment cannot be substantiated although marine inte rcalations may be expected in the eastern extension of the trough on the continental shelf. Edwards and Baker, have satisfactorily explained the source of the qu-artz, feldspar and clay as Palaeozoic igneous and sedimentary rocks. Their suggested derivation of the andesitic fragments from the Upper Devonian rhyodacite suites is unlikely as such andesitic rocks are not pre sent in sufficient quantity. As contemporaneous andesitic volcanicity is not known these fragments cannot be accounted for at present. The physiographic expression of major structures of the Mesozoic represents late Cainozoic deformation (Ch. 16). However in the Balook Block it is evident that much of the structure in the Mesozoic rocks is pre-older Basalt in age, and fromexternal evidence pre-upper Cretaceous (See Ch. 13).. M CAINOZOIC. The lower blocks of the South Gippsland Hills are covered with non-marine-tertiary rocks with outliers on the higher blocks. Detailed mapping, subdivision and correlation are extremely difficult because of lithological uniformity and lack of fossils. The Older Basalts form the only distinctive marker. The sediments are chemically mature quartzose conglomerates, sands and clays. The regional sequence is be st seen in the north-east part of the Strezlecki Block, and in the Latrobe River valley (Thomas and Baragwanath, l). Pre-basaltic sediments, the Childers Formation, contain local coal seams. The older basaltic Thorpedale Volcanics are a suite of ` olivine basalts, crinanites and rare iddingsite basalts, averaging 45% SiO; and distinguished by the abundance of titanaugite and dearth of iddingsite. An associated dyke swarm of olivine basalts, crinanites and monchiquites,and an olivine nephelinite p1ug,cut the Mesozoic along a NW-SE trend, that is parallel to the A-C joint direction of the uplift. The succeeding Latrobe Valley Coal Measures are described fully in Chapter 15. Brown coal seams occur north of the uplifted Mesozoic and can be traced easterly around the Balook Block as far south as Gelliondale. Near Sale the coal measures are overlain by marine Oligocene, and equivalents further out in the Gippsland Basin are demonstrably Paleocene to Eocene in age ~ (Taylor, personal communication). The Latrobe Valley sequence is therefore assigned to the Palaeogene. The Haunted Hill Gravels, unconformable upon the coal measures, were also 'affected by the late Cainozoic movements and may range down as low as late Miocene. Late Pliocene and Quaternary sediments, in the low-lying areas, consist of outwash gravels and sands, alluvial deposits, and near the coast calcareous dune lime stones and dune sands. Some marine sediments occur near Anderson's Inlet. The Mesozoic was planated in the early Tertiary and during formation of the thick coal seams relief was low and a very delicate tectonic balance maintained. Taylor (1966) has shown that the Baragwanath Anticline and similar structures on the Gippsland Shelf we re gradually accentuated during the Tertiary, contemporaneously with subsidence in the Latrobe River area and Gippsland Basin. The spectacular tectonic activity occurred in Plio-Pleistocene time,postdating Lower Pliocene sediments near Gelliondale. The South Gippsland structures attained their present elevation. The two main structures, the Strezlecki and Balook Blocks, are elongated en echelon uplift structures, bounded by faults or monoclines. From these a number of pinnate faults and monoclines diverge producing asiymmetric structures such as the BaragwanathAntic1ine and Gelliondale Block. Between the two main up1ifts,around Mirboo North,is a shatter zone with closely spaced parallel faults trending NE-SW. The basalts have been altered extensively to bauxite along these faults (Bell, 1961).
153 136 PH YS IOGRAPHY. The present topography closely mirrors the geological structure (Fig. Z) with the greatest relief, up to Z, 300 ft., in the two main uplifts. Dissection of the Mesozoic in these high rainfall areas has been intense producing an intricate dendritic pattern. However concordant ridge levels still express the configuration of the structures and fault and monocline scarps are still obvious. Drainage on the Tertiary. is much more open due tothe more pervious nature of the sediments. The major streams all flow on the structurally lower blocks or in fault angle depressions and are extensively alluviated in their lower reaches. Drowning of We sternport Bay is the result of Plio-Pleistocene movements with French and Phillip Islands as subsidiary uplifts within the main graben. ITINERARY FIRST DAY. MELBOURNE TO LEONGATHA. Dandenong Road to Dandenong (20 m.) crossing Tertiary sedi-me-nts: By S. Gippsland-l-lighway to Cranbourne (30 m.) - low arch connecting Mornington Peninsula to highlands, of Palaeozoic and Tertiary, with a Quarternary sand sheet extensively exploited for building sand. Tooradin (39 m.) to Kooweerup (43 m.) - cross Kooweerup swamp overlying thick Tertiaries - on right low shoreline of We sternport Bay with mangrove s,and French Island. Heath Hill monocline (55 m. ), eastern boundary of We sternport sunkland. Bass River (60 m.) flowing at foot of Bass fault scarp. Korumburra (76 m.) - deeply dissected Mesozoic of Strzelecki Block. Leongatha (84 m.) in area of Older Basalt. LOCALITY 1 - Koonwarra (93 m. The richly fossilife rous Koonwarra fish bed consists of 10 ft. of rhythmically laminated siltstone interbedded in the Mesozoic sequence. Palaeontological studies are being undertaken by J. Douglas (plants), LA. Talent, 1965 (conchostracan), F. Riek (insects etc.) and M. Waldman (fish). The drifted plant impressions include a live rwort, the ferns Sphenopteris spp. and Coniopteris, Taeniopteris daintreei, Ginkgoites australis, the conifers Podozamites and Elatocladus, the angiosperm Hemitrapa, and cone scales and fructifications. The insect impressions showing minute details of structure are principally aquatic immature stages of mayflies, midges, stoneflies, damsel flies, dragon flies, beetles and bugs, but there is also a small component of terrestrial insects. Crustaceans are represented by the isopod Phreatoicus, an anostracan, and the conchostracan Cyzicus?banchocarus. Other invertebrate remains include statoblasts of freshwater polyzoa, probable leeches, possible earthworrns, a mite, Limulus, and caddis fly cases. The fish are principally Leptolepis accompanied by Archaeomaene and a related new genus, the palaeoniscid Coccolepis, and the amiid Liodesmus. Impressions of two feathers have also been found. Riek pictures the deposit forming in a lake backwater which was subject to periodic drying. The fauna, preserved in relaxed positions, was killed by increase in water temperature and preserved he believes by a film of salt. Drying did not reach the stage of mud crack formation. With the next inundation the fossils were cove red by a lamina of fine silt and the backwater was repopulated from the main lake. IN TRANSIT. Cross TarwinFault to Meeniyan (95 m. Pass Doomburrim fault scarp on left. Fish Creek (109 `m.) - Palaeozoic of Hoddle Range (1000 ft.) to E. Waratah Bay (127 m.»mm SECOND DAY Some of these localities can only be seen satisfactorily at low tide. LOCALITY 2 -:mlm The 114 Bluff, Walkerville to Bird Rock. Liptrap Formation strongly folded, wide shear zone to main boundary fault F1 dipping steeply W. - Bluff member of Waratah Lime stone sheared at fault and calcite veining away from it, cut by shear zone with mylonite in quarry face - Kiln member - old lime kilns - gap cove red by sandy beach - Bird Rock member, brown limestone overlying grey dolomite - unconformity to greenstones with contact scoured by sea.
154 137 LOCALITY 3 - Bird Rock to Digger Island. Greenstone lavas with interbedded tuffs - serpentinised gabbro obscuring fault F2 - Digger Island Limestone. LOCALITY 4 - Digggr I_s_land to Bell Point. Serpentinised gabbro metamorphosing Digger Island Lime stone - Digger Island Limestone strongly sheared near fault F3 - Bell Point Limestone folded and sheared near fault F3 - Gair Rock, unconformity of Bell Point Limestone on biostromal Waratah Limestone - Mushroom Rock, massive to bedded Waratah Lime stone. LOCALl'I` - S. _side of Bell Po_in_t. Sheared and contorted Bell Point Limestone against fault F3 - Digger Island Limestone - fault F2 - greenstone lavas with shale intercalation and limestone lenses. LOCALITY 6 - Point Grinder. Unconformity of Waratah Limestone on greenstones with basal grit, impure lower beds, and bedded white limestone - sandy beach covering fault Fl and shear zone - Liptrap Formation. LOCALITY 7 - Cape Liptrap. Liptrap Formation - massive pebbly sandstone forming point - mudstones with interbedded sandstone bands and incongruous folding - raised shore platform - slumped beds and conglomerate containing detritus derived from axis. MEENIYAN TC) MORWELL. Doomburrim fault scarp (7m. Fish Creek lineament (9m.) - structure in Mesozoic etched out by streams. Foster (15 m.) - view of Corner Inlet, Wilson's Promontory, and Toora fault scarp. Follow foot of Toora fault scarp - narrow strip of Palaeozoic overlain by basal Mesozoic. Toora (22 m.) and Welshpool (29 m. Detour to Toora Tinfield - infaulted non-marine Tertiaries at foot of Yarram monocline. Cross Balook uplift by Midland Highway. Beech Hill (1880 ft.) (44 m. Budgeree fault scarp (64 m. Boolarra (68 m. 'Follow Morwell R. valley in faulted depression to Hazelwood (Churchill) (77 m.) - power station on right. Morwell (82 m.) and Yallourn (87 m. REFERENCES. Bell, G., Notes on the Bauxite Deposits of the Mirboo North District, South Gippsland. Min. Geol. Joyn., 6(4): Dettmann, M.E., Upper Mesozoic Microfloras from South-Eastern Australia. Proc. Roy Soc. Vic., 77(1): Douglas, J.G., The Mesozoic floras of Victoria. Mem. Geol. Surv. Vic. (28). Edwards, A. B Petrology of the Tertiary Older Volcanic Rocks of Victoria., 51(1) Edwards, A. B., A Dome-like Structure in the Jurassic Rocks of South Gippsland. 54(2): Edwards, A. B. and Baker, G., Jurassic Arkose in Southern Victoria., 55(2): Ferguson, W.H., G eological Plan, Waratah_, County of Buln Bulg, (Geol.Surv.Vic.). Gloe, C.S., The Geology of the Latrobe Valley Coalfields. Proc. Agstr. Inst. Min. Met., No. 194: Hill, D., Devonian Corals from,waratah Bay, Victoria. Proc. Roy. Soc. Vic., 66: Krommelbein, K., Devonische Ostracoden aus der Gegend von Buchan und von der Kuste der Waratah Bay, Victoria, Australien. Senckenbergiana, 35(3-4); Lindner, A. W., The Geology of the Coastline of Waratah Bay between Walkerville and Cape Liptrap. Proc. Roy. Soc. Vic., 64(2): Singleton, O. P., Geology and Mineralization of Victoria. in Geology of Australian Ore Deposits 2nd ed. Ed. J. McAndrew: (8th Comm. Min. Met. Congr., Melbourne). I
155 Y'- 138 Spencer-Jones, D., Geology of the Toora tin-field. Geol. Surv. Vic., Talent, Bull. 54. J.A., The Stratigraphic and Diastrophic Evolution of Central and Eastern victoria in Middle Palaeozoic Times. Proc.'Roy. soc. Vic., 79(1): Talent, J.A., A new Species of Conchostracanfrom the Lower Cretaceous of Victoria. mg., 79(1): Taylor, D. J., Esso Gippsland Shelf No. 1 - The Mid-Tertiary Foraminiferal Sequence. Appendix in Bur. Min. Res. Austr. _lfetrolgum Search Subsidy Acts, Publ. No. 76: Teichert, C., Note on Devonian Lime stones between The Bluff and Bird Rock, Waratah Bay, Victoria. Proc. Roy. Soc. Vic., 66: Thomas, D.E., The Structure of Victoria with Respect to the Lower Palaeozoic Rocks. Min. Geo_l. Journ., l(4): Thomas, D.E. and Baragwanath, W., Geology of the Brown Coals of Victoria, Parts 1-4, lgd, 3(6): 28-55, 4(1): 36-52, 4(2): 41-63, 4(3'): Thomas, D.E. and Singleton, O.P., The Cambrian Stratigraphy of Victoria. in _El Sistema Cambrico, su Paleogeografia X el _robl _ma de_ su Base_. Z: (20th Int. Geol. Congr., Mexico City). Waldman, M., Fish from the freshwater Lower Cretaceous of Victoria, Australia, with comments on the palaeo-environment. Pal. Assoc. London., Spec. Pap. 4 f *QVQQ -1 'Kiwi as 'sv q fb 243 *N Q v- ~» - <»,Ny v:'{, - N 1; `N`1. A -A N/,H 1:'_1N. _' A QAM; ln mwrz _ézm-.:1~:x n1:11'1:m-:e. _ 1-:.v+:1> A.w.Howi/tt - Pfwg. Rep. Geal. Su/w. Vic., 1876.
156 CHAPTER THE BROWN coals or T1-1E_ LATLROBE va;_.le _g by C. S. Gloe. The main deposits of brown coals in Gippsland occur in the Latrobe Valley Depression, which forms part of the Gippsland Basin, and also of the physiographic feature named by Gregory as the Great Valley of Victoria. The Great Valley was formed in Early Tertiary times when an east-we st depression developed between the Central Highlands and Southern Uplands. Eastwards from Melbourne this depression is broken into several units by cross faulting. The Gippsland Basin occupies three of these units and extends from near Warragul in the west to beyond Orbost in the east. In the basin, and in particular in the Latrobe Valley Depression,there accumulated a thick sequence of clays and sands with extensive brown coal seams and a series of lavas and tuffs towards the base. Continued depression in the eastern portion of the basin caused marine transgression in mid-tertiary times, which resulted in the further deposition of several thousands of feet of limestonespand marls. The we stern limit of the basin is the upthrown Warragul Block, which is covered mainly by Older Volcanics. To theeeast is the downwarpe-d area of the Moe Swamp in which a series of sands and clays with minor brown coal seams and several thick flows of basalt accumulated. The small, uplifted Haunted Hill Block separates the Moe Swamp from the East Gippsland Plains, a structural depression in which the main sequence of Tertiary fresh water sediments we re deposited. The East Gippsland Plains extend from near Yallourn to beyond Orbost and also swing around the Balook Lobe of the South Gippsland Highlands towards Yarram. s'1: ;1_AT1c-RAPH;_f_. The Tertiary succession in the Latrobe Valley Depression was classified by Thomas and Baragwanath ( ), and later modified by Gloe (1960). As a result of more recent drilling, the present subdivision of this succession is as shown in Table 1. Following extensive peneplanation in Victoria in Upper,Cretaceous to Early Tertiary times, differential uplift initiated Lower Tertiary deposition in the Gippsland area. The oldest of the se sediments is the Childers Formation (up to 12.0 feet in thickness) which included some brown coals. Overlying the Childers Formation is a series of basalt flows and tuffs of the Thorpdale Volcanic Suite, which forms part of the Older Volcanics of Victoria. The basalts are widespread in Gippsland, and, noticeably in downwarped areas, individual flows are separated by a sequence of clays and thin brown coal seams. Slow downwarping continued and a sequence of sands and thick brown coals of the Upper Latrobe Valley Coal Measures were deposited in depressed areas. Based on coal seams these sediments may be subdivided into three groups. The olde st group consists of the Traralgon Seam and its underlying clays and sands. The group is mainly developed in the Loy Yang - Gormandale area and does not occur in the we stern portion of the basin, nor along its northern margin. In the Loy Yang area, the Traralgon Seam is 200 feet thick but further east splits intoseveral seams, the combined thickness of which reaches as much as 500 feet. In the Yallourn-Morwellare a, the'fmorwel1 Group directly overlies the Older Volcanics, indicating a period of still-stand over the period take'n'for deposition of the Traralgon Group further east. The Morwell Group is a complex system of thick coal seams and interbedded clays and sands in which splits retain their identity over large areas and are given individual names. To the west the base of the group is locally associated with thin basalts which may be a late phase of the Thorpdale Volcanics.
157 140 Talile 1_- Spbdivisiori of Latrobe Valley Coal Measures ALLUVIUM Unc onformity HAUNTED HILL GRAVE LS Unconformlty Post-Yallourn Seam Clays F Yallourn Group Yallourn Seam I Yallourn Clays I' Morwell No. 1 seam Morwell No. Io Clays Upper, 4 Morweu Group ~ Morwell No. 1A Seam Morwell 4 Morwell No. IA C1ays>- No. 1 Seam LATROBE VALLEY COAL MEASURES _ Traralgon Group Morwell No. 1B Seam Latrobe -<Morwe1l Ns. 1B Clays I Seam Morwell No. Z Seam L Upper Morwell No. Z Clays Traralgon Seam Traralgon Clays. Thorpdale Volcanic Suite with interbedded coals and clays Narracan Group Childers Formation - Lower Lower Sub-basaltic conglomerates unconformity clays, coals, etc. e sf é9s& 6? < v + oc' `>+ ' Q. oc' v' Vo o' 9* 6* o' 0 /8`.>».Sy.3.-`: ' s' #3 as Q-' <9 v e1'y9'` -L' O49 Q? _*vi* gui*.cy»6' ~9 y- T' '.vrl;= W -vumsou no: ll ~uomnl L E me FEET F ET 000 al I' -=._. 7 S _mo U, _pppeop e e t e_os,s_s o.s,[il s ALE or Mins U L s H u an L ca z us LT...E n f; u LS.._..._ uzsozo.. W0 Fig. 2. Geological section across Latrobe valley. Fig. l(opposite). Geological map of the Latrobe Valley
158 N G YALLOURN t.lorwell I IoAORWELL I A.. IoAORWELL! B.. ~ k» H DEPTH TO COAL < 300' ANTICLINE E:::::::: t.lorwell Z SYNCLINE LATROBE TRARALGON ~ IoAONOCLI NE FAULT SCALE OF MILES.~ ~=- ~O~~ ~2~~3 ~4 t.l I LES - REVISED TO AUGUST 1!45' - PLAN LATROBE VALLEY OF GEOLOGY (OV~RBUROEN REM OVEO) NORWELL MONOCLINE w YALLOURN Jil40 NQCUNE YALLO URN SYN CL INE MO RW[lL AN TiCLINE TAARALGON SY NC LINE TRARAlGON MONOC LINE ROSEDALE MONOC LINE 8AAAGWANATH ANTICLINE ~ B' HAZELWOOD SYNCLINE LATROBE SY NCLINE YA Ll OUAN MONOC LINE SCALE OF SECTIONS HORIZONTAL feet FEET VERllCAL
159 141 In the central portion of the Yallourn-Morwell area the Morwell Group is represented by the thick Morwell No.1 Seam (300-soo feet thick)and the Morwell No. Z Seam ( feet thick). North of Morwell the Morwell No. 1 Seam splits into the 1A and 1B seams. The upper split thins towards the north and largely disappears 1-2 miles south of the Latrobe River. The Morwell No. 1B Seam retains its identity rather better and about Z miles north of Morwell joins the Morwell No. Z Seam to become the Latrobe Seam. Economic deposits of this seam, which has a maximum thickness of 480 feet in the Latrobe Syncline, have been preserved at three localities along the northern, edge of the basin. Here the Latrobe Seam is underlain by Z0 to 50 feet of clays which re st unconformably on Mesozoic sediments of the Tyers Group (Philip, 1958; Beavis, 1959). The Yallourn Seam is the youngest in the Latrobe Valley and is separated from the Morwell Group coals by clays and sands ranging in thickness from a few feet near Morwell to over 400 feet south of the Latrobe River. As a result of tilting and subsequent erosion, the Yallourn Group is missing from the north-west corner and along the southern flank of the basin. The Yallourn Seam retains its maximum thickness in synclinal areas feet in the Yallourn Syncline. Over much of the Loy Yang area, where the_coal measures have been folded into a broad dome with a number of small sharp ancilliary structures, the interseam sediments separating the Yallourn and various Morwell Group seams are thin, and, in places, missing. As a result it is possible to find up to 750 feet thickness of continuous- low ash content coal in this area. The Morwell No. Z Seam splits into several seams towards the south of the dome but the Morwell Nos. la and 1B and the Yallourn Seams maintain their individual thicknesses over large areas. A brown coal seam up to 143 feet thick occurs on the eastern end of the Baragwanath Anticline before it plunges to the east beneath the mid-tertiary marine sequence. This, the Coolungoolun Seam, is considered as probably belonging to the Traralgon Group. The contact between the Coolungoolun Seam and the overlapping marls and limestones appears to be an angular unconformity indicating uplift and erosion prior to submergence in mid-miocene times. Sometime after deposition of the coal measures ceased in Gippsland the sediments were disturbed by uplift and folding. This was followed by widespread erosion as a result of which a considerable volume of the sediments, including coal seams, was removed. At this time coal was exposed over large areas and caught fire at a number of localities. The fires burned large holes in the coal, reaching up to 1, 200 feet across and 160 feet deep. The holes were subsequently filled with clays and silts but in some places the fires continued to burn and the sediments became fused at temperatures up to 1,300-1,400oC (Grubb, 1963). Further earthmovements in Plio-Pleistocene times rejuvenated streams and the widespread Haunted Hill Gravels were deposited over the eroded surface. Continued slight movements and erosion by the present river system has resulted in a considerable variation in thickness of these gravels, ranging from less than 30 feet to more than 300 feet. The major cuts in the Latrobe Valley are located where the thinnest gravels overlie thick coal seams. STRUCTURE. The Tertiary sediments occupy an elongated, asymmetric, east-gaping syncline, the axis of which runs roughly east-we st and just south of the Latrobe River. Within the depression there are a number of tectonic structures, some of which have been topographically preserved as a result of late stage movement. The major structures are the Yallourn, Morwell and Rosedale Monoclines, the Loy Yang Dome and Baragwanath Anticline. It is generally considered that the monoclines are subdued reflections of faulting in the basement rocks and that the synclines and anticlines formed mainly in response to this differential movement. Indirect compressional folding and differential compaction may also have caused a number of the structures shown on the accompanying map. Faulting does not appear to be widespread in the Coal Measures and is mainly of a minor nature. No faulting has been observed in the Yallourn Open Cut, which now has a perimeter of 7% miles, but numerous small faults occur in the Morwell Open Cut, and to a lesser extent in the Yallourn North and Yallourn North Extension Open Cuts. These faults, most of which are normal, appear associated with the adjacent strong monoclinal flexures. Both high and low
160 142 angled reverse faults have also been observed. A small overthrust involving the Mesozoic basement was exposed in the Yallourn North Open Cut. Both the Yallourn and Morwell Seams, as observed in their respective open cuts, are strongly fractured. In Yallourn these cracks, which have been traced for distances of over half a mile, and penetrate the full thickness of the seam, break up the seam into a number of huge blocks. The orientation of the fractures indicates their tectonic origin. Many of the cracks, which opened up to as much as 18 inches, are filled with sand derived from the overburden, and in some secondary marcasite was deposited. The fractures in the Morwell Open Cut are far more numerous but the width of opening is much less. Here they have been filled with clays and silts, with occasional silica and marcasite veins. Their orientation is far more constant than at Yallourn and they tend to occur concentrated in zones. Ao;_91j T_l -IE coal MEASURES, Apart from plant remains no fossils have been found in the Coal Measures and hence the age is,deduced by their association with known other rock groups. The Upper Latrobe Valley Coal Measures are younger than the Older Volcanics, the main flows of which are regarded as of Eocene age. Similarly mid-miocene marine sediments overlie the Coolungoolun Seam (Traralgon Group) with an apparent unconformity. The age of the Upper Latrobe Valley Coal Measures is considered therefore as probably Oligocene, possibly extending upwards into Miocene. Recent palynological work by Harris (1966) suggests that the Traralgon Group is of Eocene age but that the Yallourn Group may be as young as mid-miocene. While this range appears rather long, it does agree with the general concept that the Latrobe Valley Depression developed gradually from off- shore to.the west (inland) and that diachronous deposition of marine and fresh water sediments took place over this period. PALAEOBOTANY OF THE LATROBE VALLEY BROWN COALS. It is usually accepted that conifers formed the greater part of the plant material, and in particular of the wood, from which the brown coals were derived. The preservation of certain plant remains has allowed the identification of Agathis, Araucaria, Dacrydium, Podocarpus and Phyllocladus. Little well-pre served angiosperm wood has been found in the brown coal but plant remains of Casuarina, Nothofagus, Myrtaceae, Sapindaceae and Proteaceae (Banksieae and other tribes) have been de scribed (Duigan, pers. comm. COAL COMPOSITION. Brown coal is extremely complicated in composition (Baragwanath, 1962). It consists largely of partially preserved plant remains intimately mixed and impregnated with amorphous humic substances, which form the bulk of most brown coals. The nature and relative proportions of plant remains reflect the variations in depositional conditions which caused the formation of different coal types within the seams. Edwards (1947) found that 95% of the Yallourn Seam in the Yallourn Open Cut consisted of alternating bands of what he named lignitic and earthy types of coal, and that the se showed slight but distinct chemical differences. A further coal type which, although fairly common, makes up only a small proportion of the total volume, is the 'khaki' or pollen-enriched coal. If is Chemically and physically quite distinct. The most important chemical properties of brown coal are ash content and inorganic constituents, moisture content and heat value. Ash Content - The ash content of the various seams in the Latrobe Valley normally ranges from 1% to 4% on a dry basis although occasional values may reach 5% or drop as low as 0. 5%. Despite such low values, certain inorganic constituents may occur in undesirable concentrations, affecting not only the burning properties of the coal but also the tendency to slagging or fouling of heating surfaces in boilers. ln some areas the amount of sodium present in the coal is sufficient for it to be classified as a 'salty' coal. Moisture Content - The moisture contents of brown coals in the Latrobe Valley reflect the degree to which the coals have been consolidated due to the pressures of stratigraphical burial or of folding (Edwards, 1948; Gloe, 1960; Rosengren, 1963). As a result there is an overall reduction of moisture content with increasing depth, but the rate of reduction is far from uniform
161 143 Calorific Valu_e_ - The gross dry, ash free calorific values of most Latrobe Valley brown coals range between 11,000 and 12,000 B.T.U's. per lb. The quite high, but widely varying moisture contents (50% to 70%) of these coals reduce their heat value to from 2,600 to 5,000 B.T.U s per lb. on a net wet basis. It will be obvious that such low rank fuels can be economic only where large reserves occur at shallow depth and can be mined at low cost by large scale, modern equipment. RESERVES _ Reserves may be calculated on a geological or a mining basis, and the latter in particular have to be clearly defined as to limiting factors such as batters, coal to overburden ratios, depth of open cut, location of towns, rivers, etc. On a geological basis the reserves in the Latrobe Valley are calculated as 47, 500 million tons proved and 37, 300 million tons inferred. Of the proved tonnage some 29, 000 million tons occur with less than 100 feet of overburden over the uppermost seam. Selecting the most economic areas, from which sufficient coal to satisfy power stations could be supplied at present costs and subject to limiting factors available, re serves would be approximately 10, 000 million tons. G_EOL_OGIC_ L FEATURES INF LUENC 1 NG_ MINING. Stability, _. (a) Landslides - While normally dips are at a sufficiently low angle to prevent landslides along bedding planes, local steepening of dip occurs in some marginal areas. Several.slips have occurred and are considered to have been due not only to an unfavourable angle of slope but also to the build up of pore water pressures in some permeable stratum. (b) Earth and Coal Movements - All excavations, whether open cut or underground, are subject to movement following readjustment of stresses disturbed by mining operations. The amount and nature of these movements is controlled by such factors as the physical properties of the rocks involved, the incidence of planes of weakness such as joints, faults, certain bedding planes, etc. and any' build up of hydrostatic pressures in these planes, the slope of permanent batters, etc. The problems in the Latrobe Valley are unique, as nowhere else do such thicknesses of continuous brown coal form the major part of the permanent batters of open cuts. As described earlier the Yallourn and Morwell Seams are broken into huge blocks by major joints, and also faults in the case of Morwell, and it has been found that the general stability of batters is determined more by these planes of weakness than by the strength of the coal itself. This is apparent in operating faces which are dug at relatively steep angles. The widely spaced cracks in the Yallourn Seam have allowed some movements to occur but have not resulted in serious instability. However, the complex locally intense jointing at Morwell has resulted in a number of coal falls with some damage to dredgers. The inward and downward movement of the ground surface adjacent to open cuts is also of importance as large structures such as power stations must be founded in areas with low differential movements. Underground Water_ Sands in the interseam sediments hold water under sufficient arte sian pressures to allow the water to flow at the surface in low lying areas. As open cuts are deepened the pressure exerted by weight of coal and any clay aquiclude is reducedand could eventually become less than the arte sian pressure. At that stage stability would be~maintained only by the shear strength of the overlying materials, which, due to fracturing, is liable to be low. Such conditions exist at Morwell Open Cut and it has been necessary to progressively lower the piezometric surface as the open cut has developed in depth. A lowering of 200 feet had been achieved by September, 1966, by means of flowing arte sian bores located in the deepest sections of the open cut. For future development it will be necessary to lower the pressure surface at a faster rate and this will be done by the use of bores equipped with pumps.
162 1 ;:~-_~~» 144 REFERENCES Baragwanath, G.E., Some aspects of the formation and nature of brown coal and of the behaviour of brown coal ash in water tube boilers, with special reference to Victorian Deposits. Proc. Aus. Inst. Min. Met., 202: Beavis, F. C., The relationships of the Latrobe Seam at Yallourn. Proc. Ro. Soc. Vice; Edwards, A. B., Coal types in the Yallourn and Latrobe Brown Coal Seams. _12_r_Q_c_. A1150 Inst. Mina Mets: Edwards, A. B., Some effects of folding on the moisture content of brown coal. E_1 _q_g_. _A us. Inst. 1 /Qin. I_{_Iet_,_ : Gloe, C.S., The Geology of the Latrobe Valley Coal Field» Grubb, P, L,C., Fused siltstone from Morwell, Victoria...1_/1_i_t_1. Investo 'l Harris. W.K Symposium of Pa 1ynO1QSYg Geslf S C Aust-» SP<-=<=is1iSfS' ins» Adelaide (discussion - unpublished). Philip. G.M.. 195% The Jurassis sedimsnts Qf the Tvs G1' up» GiPPS1snd< Vi t 1 ia- Rosengren. K. J CQI1SQ1iC19»tiQn Qf Sums Viswriarl Brswn Cvalsv Inst.: Min. 208: 157'l,933 Thomas! DQE, gud Barggwanath, W., CisQlQ3Y Qi the Brown Goals Qfvictoria, Parts 1-4, Mig. cegi. Jg_ u_1 (YiC~) HQ; 3-5% 401% 36-52; 4(2)= 41~63= 4(3)= _ -',v~'..-a: ' ;- ;..1 ),' 'I ',_,»>/?I/.ty ~, : ;$~' _(I V.-._,_. /»» pl/ /] 1 - W I/»»,.u //.-/ (_ JL? F (L M._ r 9-.tp [ _ _H` _(I/I sl, new., LcRo::,:; 'rum l/1`l 1`C`1[1-L.1;LiRD/'1:1R`VM,L}lY Hao M' NEAR G_ :UN'l' A.w.HowL1>t - Pfwg. Rep. Geof. Su/w. Vic., 7878
163 CHAPTER LATE CAINOZOIC GEOLOGY AND GEOMORPHOLOGY OF SOUTH-_EAST GIPPSLAND bv J. J. Jenkin L The area concerned (Fig. 1) extends from Wilson s Promontory to Lakes Entrance, and the following aspects are discussed. l. Tectonic control of the gross morphology. Z. Pleistocene and Recent coastal forms. 3. Fluvial and lacustrine forms of the Gippsland Lakes. 4. The effect of engineering works on coastal processes at Lakes Entrance. _l_. TECTONIC CQNTROL OF_THE GROSS MORPHOLOGX, The large-scale morphology of south Gippsland is chiefly influenced by tectonic factors which can be traced to the Palaeozoic, although indications of the present configuration only appear in the Mesozoic. The main outlines were defined by early Tertiaryearth movements, accentuated by strong movements in the late Pliocene to early Pleistocenef The clearly defined morphotectonic units, bounded mainly by normal faults or monoclines (Loc. 1) _are shown in Fig. 2 and briefly described in Table l. Uplifted blocks are broadly arched (anticlinal horsts) and depressed blocks are broadly synclinal (troughs). Within each major block there is a variety of subsidiary structures including normal faults and monclines, high- and low-angle thrust faults, anticlines, domes and synclines. and water drilling and, in some cases, suggested by geophysical work. These have been shown by coal, oil Palaeozoic rocks do not outcrop, but in adjacent areas form the main sources for many of the later sediments (see ahead and Chapters 14 and 17). Lower Cretaceous and possibly Jurassic feldspathic sandstones ('arkoses') and mudstones form the bulk of the upthrown blocks of the South Gippsland Highlands. In the sub-surface they extend south-eastwards, beyond the coast, and eastwards to about Paynesville, being in a trough extending from Western Port to somewhere beyond the Ninety Mile Beach. In the early Tertiary the surface of these was affected by erosion, river gravels, sands and clays and some thin brown coals being deposited as valley fill and sheets on an apparently very subdued surface. These were then covered in the western part of the area by extensive flows of Eocene or Lower Oligocene basalt. Broad down-warping apparently occurred before extrusion of the basalts, as the sub-basaltic sediments are much thicker in some places than others, particularly in areas which are still negative e. g. near the coast south of Woodside. Although thick accumulations of basalt have been preserved in down-faulted areas, whether or not these were originally thicker than elsewhere is uncertain, because extensive erosion has occurred on the upthrown blocks. Extensive earth movements followed and a great thickness of coal measures was deposited in the depressed areas. The basalt - coal measure surface is_ erosional in places but this may not be general. Earth movements apparently continued during deposition of the coal measures as the coal seams thin and split approaching the marginal faults or monoclines (Thomas and Baragwanath, 1949). The occurrence and structure of the brown coals of the Latrobe Valley are described in Chapter 15. _ Later in the coal measure period,the main Tertiary marine transgression commenced, producing some intertonguing. The main marine sequence ranges from Oligocene to Lower Pliocene in age. Away from the basin margins it is apparently unbroken, no unconformities having been detected. However, on the Baragwanath Anticline just south of Sale, the post- Lower Middle Miocene is missing and the earlier (Longfordian) rocks are strongly affected tectonically. It is probable therefore that this structure originated in the Middle to Upper Miocene and formed a peninsula extending seawards from the we stern margin of the basin.
164 146 The upper part of the sequence (i.e. the Lower Pliocene Kalimnan) is in general the regressive phase. However, it _is locally transgressive as at Gelliondale near Corner Inlet. This is probably the result of down-warping in this area. Later in the Pliocene the re was further downwarping in the coastal areas and along the Latrobe Valley. This formed the sites for the deposition of thick sequences of essentially nonmarine gravels, sands, and clays, often carbonaceous with occasional thin coals (Boisdale Beds). There were minor re-advances of the sea at this time in some localities, e.g. in, the vicinity of Lake Victoria, Seaspray and Corner Inlet. The deposition of the Boisdale Beds was followed, unconformably at least in part, by the widespread deposition of the Haunted Hill Gravels. This event is tentatively correlated with the uplift of the highlands early in the Kosciusko epoch. The 'Gravels' we re deposited as fans and aprons along the highland margins and out on to the plains, where they become progressively finer. The composition of the gravels reflects the nature of the highland source areas. In the west they consist predominantly of granitic and reef quartz, but further east a greater variety of rock types appears including Devonian quartzites, rhyolites and porphyries, as well as granite, and reef and granitic quartz. There is a high proportion of sand and clay in the formation, both mixed with the gravel and as separate beds. The Upper Cainozoic stratiis shown in Jenkin (1968) _ Earth movements continued and reached their culmination after deposition of the grave1s,' which were warped up on the flanks of the highlands, and elsewhere form the caps of tectonic ridges e. g. on the Baragwanath A.ntic1ine. This peak was probably reached early in the Pleistocene. The earth movements waned gradually through the remainder of the Pleistocene, but there is evidence of some movement - the warping of strand lines near Woodside - in the late Pleistocene. Recent movements are also possible, but it is difficult to distinguish their effects from those of sea level fluctuation. The history of post-palaeozoic earth movements in Gippsland is summarised below: Recent:? Slight depression at the E. end of the Latrobe Valley and at Welshpool (Corner Inlet area). Late and Middle Pleistocene: Warping of strandlines, Woodside area. Warping and tilting of Pleistocene marine terraces. Early Pleistocene: ) Late Pliocene: ) Extensive faulting, monoclinal folding and warping of Upper Pliocene sediments. Middle Pliocene: Broad downwarping. Lower Pliocene: Local downwarping. Late Middle or Upper Miocene: Movement on Baragwanath Anticline. Oligocene: Extensive downwarping of coal basins. Eocene: Extrusion of Older Volcanics.? accompanying earth movements. Lower Eocene: Local downwarping. Middle to Upper Cretaceous: Erosion. Lower Cretaceous? Jurassic: Rise of land areas to the north (Eastern Highlands) and? south. Formation of southern Gippsland fre sh water depositional trough. Fig. l (opposite). Quaternary geology of south-east Gippsland.
165 QUATE R NA RY GEOLOGY o F SOU T H -E A S T GIPPSLA NO. RECENT D LATE P LEISTOCENE 0 Alluvium Alluvium and swamp deposits Sand ridges and marine deposits Sand ridges.'.. EARLIER PLEISTOCENE Alluvium and marine deposits ~; ~ _. ' '' Sand ridges ~ r,-..- Terraces Mis :J '..<.A',-' Tectonic scarps Limit of Pleistocene marine transgression -,- Route 0 Stops
166 ' TabIr, 1 - Physiographic Characteristics of the Morphotectonic Units Unit Topography K:Koeppen T:Thornthwaite Climate Soils Vegetation Land Use Eastern Highlands So~thern Uplands i) Warragul Block ii) Narracan Block iii) Tarwin Block iv) Balook and Gelliondale Blocks v) Baragwanath Anticline Gippsland Sunklands i) Latrobe Depression Deeply-dissected plateau reaching 4,500 ft. ; with highe r re siduals. Structural and stratigraphic control of erosion pronounced. Maturely dissected blockfaulted area of initial low relief. Mainly 500 to 2,500 feet. K: cfb Mountain soils: podsols loams and T: BB'r skeletal soils; high moor peat. Upland soils podsols, skeletal red loams (on basalt), rendzinas and terra rossas {on limestones}. Dense eucalypt forest sub-alpine vegetation in higher parts. Eucalypt forest with dense undergrowth. Grazing on sandy loam areas. Timber. Limited dairying, grazing, timber. K: C b Loams and clay loams Eucalypt forest Dairying and sheep T: BB'r somewhat podsolic (on with dense under- grazing. Mesozoic sediments). growth {mostly Red Loams (on basalt). cleared). Sandy podsols (on sands). Broadly arched area becoming K: cfb Sandy loams, podsols Eucalypt forest Cattle and sheep narrower and lower towards the T: C.B'r (on sands) and peaty with dense under- grazing. Pine east (1,000 ft. to 100 ft.) swamp soils. g:r9'wj;h. ~lantations. a) Broad alluviated valley with lateral terraces and surface remnants. b) Coastal terraces with sand ridge s rising to 500 ft. Coastal sand barriers. K: C b T: CB'r Acid clay loams with Eucalypt {forest alkaline subsoil (on red gum) forest alluvium). Sandy loams (mostly cleared). on older clayey sediments. Podsols on sand. Peaty Eucalypt-Banksia swamp soils. forest with heavy undergrowth. Melaleuca, reeds, etc. Timber. Limited grazing. Dairying when drained. ii) Stradbroke Block Coastal terraces with sand ridges. As for (i) (b) iii) Alberton Depression Coastal terraces with sand ridges. K: cfb Sandy loams Coastal sand barriers. Alluvial T: CB'r As for (i) Latrobe Depression flats of main streams Irrigation, dairying and stock fattening. Cattle and sheep grazing. Pine plantations.... ~ -J
167 148 Z_=_ PLEISTOCENE AND RECENT, CO!_ STAL FCRMS. The main Pleistocene and Recent physiographic forms occurring in the coastal areas of south-east Gippsland are set out in Table Z. RECENT: Table Z - Pleistocene and Recent Coastal Physiographic Form s. _ea Lev_e_l (S: L;) heights,l are relative to present H. W.M. Adjustment to pre sent Outer coastal barrier, Ninety Mile Beach. S.L. lagoons, dunes, marsh. Coastal lakes, silt jetties, Gippsland Lakes (Eagle spits. Point, Paynesville, Lakes Entrance). S.L ft. Barrier spits -and islands; Corner Inlet, Gippsland cliffs. Lakes. Alluvial deposits. Main stream valleys. Rising S. L. Marine and alluvial Main stream valleys. deposits. PLEISTOCENE: Very low S.L » Entrenchment S.L. + (20-25 ft. (Barriers, marine terraces, Corner Inlet, Lake Victoria. (cliffs. S. L ft. Flood plain deposits. Sale, Clydebank, Bairnsdale. Low S. L Entrenchment S. L ft. Marine terraces, barriers, North of Lake Victoria, spits, bars. River terraces. Stratford, Bairnsdale. Fluctuating S.L. Marine deposits and Woodside-Stradbroke. Considerable tectonic terraces. activity. Fluviatile deposits. Stratford-Bairnsdale. The Quaternary history of this area has been one of alternating advance and retreat of the sea, producing a complex of inter-related marine and terrestrial erosion forms and deposits. Marine lterraces. (Sections 5, 6, 9, see Itinerary). Flights of marine terraces are present to the north and south of the Gippsland Lakes extending south-westerly to Corner Inlet (Fig. 1). The se terraces are characteristically flat expanses of sandy clays, sands and occasional grave-ls which are backed by a distinct cliff or by a slope steeper than that of the terrace, on which lie sand ridges and swamps often with distinct forms and associations. The cliffs which form the inland margins of the terraces become progressively more subdued with increasing elevation. The se cliffs face the ocean and link up with flights of river terraces on the sides of valleys of the pre sent streams. However, the two sets have different trends and meet in an angular junction.
168 149 Sand Ridges. (Sections 6, 9). The most prominent features on the marine terraces are sand ridges, often with very distinct alignments. The trends of the ridges are strikingly consistent within a particular area, but vary systematically across the area as a whole. Near Stradbroke the trends are about N60oW but further to the northeast towards Lake Wellington the ridge trends swing progressively to an east-west direction which is parallel to those north of the Gippsland Lakes. It seems probable that these ridges or groups of ridges are former sand barriers and/or foredunes and that they mark the successive positions of the coastline (Fig. 1). The lower parts of many of the ridges exhibit 'beach bedding' and often contain material which is too coarse to be wind-blown. However, the tops of the ridges, particularly the more prominent ones, contain finer material with aeolian bedding (Locality Z). Blowout forms, e.g., depressions having crescentic lee ridges and _often containing swamps, are quite common in the sand ridge fields. (Sections 6, 9). ;_I_ e1:_ra_g_:e_fl_ats. (Sections 5, 6, 9). Between the successive sand ridge groups, and to the seaward side of them, are broad flat areas which are inclined to be swampy. Smaller are as of a similar nature also occur within the sand ridge fields, either completely enclosed or as re-entrants from the more extensive adjacent flats. The deposits on the flats consist of sands, clayey sands and fine clayey gravels, coarser gravels being more common in the area north of the Gippsland Lakes. The se sediments bear a very close resemblance to those in the lagoons, tidal flats and marshes of the present coast. Peaty deposits are common, but are usually quite thin and appear to be a later acquisition. The flats on the seaward side of the main ridge fields carry isolated ridges and rises of sand and silty sand whose orientation in relation to the pre sent drainage, as well as their frequently elongate form, suggests that they originated as submarine bars, shoals, small barrier islands and spits, and are not remnants of formerly more extensive sand sheets. The depressions on the coastal terraces are often swampy and are broadly of four type s; (i) ' Isolated depressions of variable shape having no connection one with the other. (ii) Swales and blowout depressions of the sand ridge fields. (iii) Low-lying areas within, and re-entrants into the sand ridge fields. (iv) Narrow, sinuous depressions which are either unrelated to the present drainage system or which have produced anomalous features in this system. Depressions of the first type probably represent former sea floor depressions as they are not associated with fluviatile activity nor are they wind deflated areas, as no aeolian ridges are present. Those of the second type are either original features, being the hollows between successive ridges, or secondary features resulting from blowout. The third group is comparable in form and situation to areas within the later coastal barriers which have become isolated by the growth of a new barrier to the seaward. Those of the fourth group, in the form of interconnected sinuous swamps, are not associated with the main drainage of the area and sometimes form loops completely surrounding patches of slightly higher land or occasional sandy rises. The heads of these swamps are situated in re-entrants in the sand ridge fields, in depressions in front of these fields, at the foot of an old cliff or in an inlet in the cliff. Some of these depressions are continuous from one terrace to the next, and some of the lower ones are entered by tidal waters at the pre sent day. Their pattern and curvature is very similar to that of the present tidal channels and it is probable that they represent stranded tidal systems. The Effect of Stranded Coastal Forms on Drainage. Parallel sand ridges govern the direction of local streams, some of which become tributaries of larger streams,and others drain into local swamps. Some of these watercourses cut ac ross the ridges at low points producing a rectangular stream network. Many of them retain directions inherited from the original Swales even though the,sand ridges have been
169 150 removed or reduced to sandy caps on the intervening divides. The flats occupying old coastal lagoons are sometimes followed by streams, e.g., Merriman's Creek between Stradbroke and Seaspray (Section 6), or act as sinks into which local drainage flows, e.g., the peat swamps at Gelliondale. Sand Barriers and Spits. (Localities Z, 3, 7) The sand barriers of southeast Gippsland developed adjacent to a coastline of variable form with embayments and inlets separated by straight cliffed sections facing the open ocean. This is particularly apparent with the younger barriers (late Pleistocene to Recent) which are also the best preserved. There are three of these younger barrier groups (Bird 1961, 1965 ; Jenkin, 1968) the first of which started as a spit growing out from the southern lip of the embayment now occupied by Lake Wellington. It extended eastwards beyond Sperm Whale Head probably as a line of barrier islands. The sea level at this stage was at least 2.0 feet higher than at present. The barrier regnnants consist of a series of parallel ridges trending at about 500 in the Seacombe area to 70 on Sperm Whale Head. The ridges have been considerably modified by wind action, with the production of numerous blowouts. The material in the ridges ranges from medium gravel to fine sand- In the Welshpool-Port Albert area (Section 5) another barrier group, probably equivalent in age to the Sperm Whale Head barrier, is pre sent. This barrier is now broken at several` points, e.g., by the estuaries of the Albert and Tara Rivers which may mark the positions of original entrances. Except for St. Margaret Island, this barrier lies entirely on the mainland, not being separated from it by extensive lakes as in the case of the Sperm Whale Head Barrier. The widths and distances apart of the ridges are similar -in both areas, and the dunes are of similar height i. e. up to about 100 ft. The Welshpool-Port Albert barrier is made up of several groups of sand ridges trending in a general east-we st direction between which are extensive inlets now filled with peat and other swamp deposits. The se are connected to what were apparently entrances (tidal inlets) during the growth stages of the barrier. After a major fall in sea level (probably to be correlated with the Wurm glaciation), the succeeding barriers formed at the time of a subsequent rise of sea level to a little above that pertaining at present. These barriers occur in the Corner Inlet area, where they consist of islands of very complex form, and in the Gippsland Lakes area where both barrier islands and spits occur and their form is relatively simple. Internally, the beach ridges of these barriers exhibit aqueous ('beach-type') bedding which is now up to 7 feet above present H.W.M. _This feature, together with landward terraces containing marsh sediments and rising to five or more feet above H. W. M., shows that these barriers have emerged. Consistency of elevation over the whole of the area suggests that this emergence is due to a fall in sea level of about 7 feet. The pattern of the beach ridges reflects the direction of approach of refracted swell and wind waves at the time of their formation. The complex beach-ridge patterns in the Corner Inlet area show that wave conditions there must also have been correspondingly complex. The sand-ridge units making up this barrier group are of three types: (i) Long, narrow barrier islands with re-curved spits at both ends. (ii) Barrier spits, often curved and generally with strongly re-curved distal tips. (iii) Cuspate forelands. The junction between successive units is frequently erosional and marked by a subdued cliff and/or a line of dunes.
170 151 The barriers are, or were, separated by tidal channels, the main channels being maintained throughout the development of the barriers. With minor channels, however, barriers developed across their entrances which were then displaced laterally or completely closed. The youngest barrier, the present outer barrier, is an almost continuous complex of beach ridges and sand dunes extending from Corner Inlet to beyond Lake Tyers (Localities 3, 7). At Corner Inlet it is broken by several inlets and consists of a series of arcuate islands lying end to end. From this area eastwards it forms the broad arc of the Ninety Mile Beach which extends, with minor breaks only, to Lake Bunga. 3- FLDVIAL ALLD LACLISTRINE FORMS QF. The marine transgression which followed the last major lowering of sea level initiated estuarine and deltaic deposition in the drowned valleys of the main Gippsland streams. Barrier formation in the mid-recent and again in very recent times, produced a large body of water largely isolated from direct marine influence - the Gippsland Lakes. Extensive fluviatile deposits filled the drowned valleys and extended into the lakes. In the Corner Inlet area, enclosure of the lagoons has not been so complete and both fluviatile and marine deposits' are being added to the deltas at the present time. The delta flood plains in the Gippsland Lakes area consist essentially of levee, levee breach and back swamp deposits. The streams consist of long, straight or broadly curving reaches connected by gentle bends and in any one valley there is one main stream from which abandoned or intermittent distributaries occasionally diverge. The form of the streams in their lower parts is in marked contrast to the meandering sections further upstream. The delta flood plains have resulted from the prolongation of the river levees into the lakes with the formation of lateral swamps by progressive isolation from the main body of lake waters. The Latrobe, Avon, Tambo Rivers and in particular the Mitchell River (Fig. 6) terminate in silt jetties projecting into the Lakes. The re are two main schools of thought as to the origin of the jetties - (i) Bird (1962) and most earlier authors consider that the jetties grew out into the open body of lake water. (ii) Clifford (1949) and Jenkin (1968) consider that they are levee remnants of a drowned flood plain. Other conspicuous deposits forming in the Gippsland Lakes are marginal swamps and spits attached to headlands and islands. The spits re-curve in different directions depending on the available fetch across the Lakes and the refraction patterns of the waves which are related to variable wind direction and the form and position of the lake margins. 4. THE EFFECT OF ENGINEERING WORKS ON COASTAL PROCESSES AT LAKES ENTRANCE (Fig. 8, Locality 7). The construction of an artificial cut through the outer barrier at Lakes Entrance has had several marked effects on land forms at Lakes Entrance and probably for some distance into the Gippsland Lakes. These are (i) The progradation of the Ninety Mile Beach adjacent to the retaining walls of the artificial entrance. (ii) The comp1et_e closure of the old natural entrance to the Lakes by sub-aqueous sedimentation and the migration of U-dunes over the silted-up area. (iii) Increased tidal flow in and out of the Lakes resulting in increased salinity within the Lakes which has destroyed some of the marginal vegetation (although the extent of this effect is the subject of debate). A lunate bar has also formed seawards from the entrance.
171 V Q Y C»* / /' g if 4 Y PQO5 // / ~ Q4 <69 5 / 1/ J D / 1 go% cm / ,P~ < MOE / ' _- Q8 / - / Q, ;. g_, sun < _ANo /Np<» E, im/ f ; / (5 NP` -(Cf I6 M1165 Q`P_C/v` W / I /' Z $ O _,J ' / /~ r~v~'` A // %' / *_ $ 9 ;_..._.._l.j,ll O* I/ I'-. **, I:,v~<=,Oc, L C / 0,9 EASTERN»-ual-u_ANDs % 11/,Il,I /'_-` /<<>~ * sour:-iern UPL/mos»'/ l~ 'I % 1/ 5 -''' lui /I,- K_,-..- ' Warragul Block QV /% O A f / Z X 9 Narracan Block /?~ q / ` -5./ 09? Balook e Gelliondale Blocks &v_q` 4 _ '`T~_<O C? GQL BLK v Baragwanath Antlcllne 75 5 // Tarwln Block GIPPSLAND SUNKLANDS ' Q7 Latrobe Dep 4. Moe Sunkld Stradbroke Block Alberton Depresslon F/G 2 S OUTH EAST GIPPSLAND MORPHOTECTONIC UNITS I 1 ` '`.f `r I '1 ` ` O an-nil Q <`~,.J-»' '/ ` Abandoned cllff >~_/,>' I I I I (. 0 I *ll 1-, ww' {' ` [AX o._ 9 - Y <> 70 /f -_ <~ _._..:... s ff ' 0 G# 1 Q Oo `4;'_ _ McLaugh ns 3 _ (_ / `/' ' `ZI_TI5>-'~= = /~, P als* / O 1' 8 ' ~,-> ' ~ A `q v /V/' if/ és L S v'~ ' A,»-~-, Q / Q? _/ fe/ tk Q O /I New entrance 1' /( / I GI/ / 9~ if I / /Z /I S I 6 J` -_ ` gs ', I 9. I ~ `.,_> I/'( 7, I S 6 M .,-' ',/ S 2-1 `i Washovers' F/G 3, STOP 2.
172 Letts ` 153,x 1 `- _ ,'7f/ o Q ' 'J * j 1/ I O O / ( in 1 ` ` T I l 7' Q Z xf o ,' { /;--3 / ' écif / ` f l 1 e, 6, 0 / `1 /--:J ._ 0 ~» / I/ Q»,>, ii-l ` /* *, Q ` Y `» /1* -;,_../ 0 ~ 4 `. I Q/ ''l N / b Mile.» /7,ff, 3 **'g 1 0 If af 2 U 2.2 ' ~' 2~`0 5,110 /0 I /' L... L ' `_, - » ' `~* I ._ /: <-r-'a: / O :'`:;':: 'QY a7 4 ` Jones Bay -4 gf' 'Q lg,. f ` }* w L / L N ky ake K/ng 'li 1 1 G/,_/4 -- I* gf' 'lr O»' Za Q»=-1161'» - 4,/Q, _l _gf. `*` I 1' O A ` & f/ QQ /` Beach }'` ' A _lf 7: 'Is' `:$ _Q ~` Q , L30 <7 _, :_ f -I --'A l /i/i G 2 L /I' I/ O _` :.~,~» /~/ agle Point ` m;?.. `» I O ' o o I/ ` ff* // I (s Z _.;;;~»» t /ff gf-gf; g I 9 -_, ' f>'1, /,' I O '_)/ <s ' Mul., ' gf*, FIG. 4, srop 3. f _. _;.1,I at O O I ` Mile I I '` ` ` FIG- 1. ' /2 & _, )',*`'~4 -» 1 s/ -`, ',»F~' ' '* ~L` 1 4-» / ' an _ I ( C Y /'_ =,f~`» 'L v,.v ` `* _6 ` ~ / g * _ -~`*` '`-/,/ - ' `~ vw.a 7, sro/= '»-r '~> f' gb ' ` >` v H _:var J),/ I > /<3 :-7 ;. I 8, _ E _-* c rl( I n If ` / _.re S ~ I _2 U-G -.. M,.-4 '?` * J I '7 ri A E _g// *gg I. /` s Q/ / `_ 5' 4 5' ' y O I I-,JT '_ r P _ QJ w i Wi? -`,' ' `&:-J » ~,-,2 f uv:-r~'> ~' `_ I /.._ * ` 5 _-r,» '»'.,4 I CIy]ebank,C ;:>_ > __'_ * ' /0 ~,b/ I },»' `, _;,.` 9/7/,_ ik,` /'I ,as / ` 4 ' J: K?/ ~,.8; `:v 1' _,-/ eff,` ',»f C`e L_ ', Q,/ _,_ -;=» `,r_ ~»`»,I-rf #pf ;' ',»--~ _?=- 1*---~;c, ,rf F/cs. a, srop z L _`,.-.,.` ---_`~=~, I g. I-:,_ I,ga 'N u* _L;_,.' ;f b ' `-* ~» '~` I0 ' ` `é,.-..;,»',» _:`$ 'l-ll ;` Q.,` ~--- ' D' J ' I» 1' Q '` ~ `,.,_ ';~ ' ; LEGEND FOR FIGURES 3 TO 6. I ` I /'`-'` /- ' ' ;' '`~' c' Il If.; // L_ Sandy beach `~ ' f 15 F/6. 5. STO 4. 1 _._-JL- f?,»?',_ /?f'> '` ~ M e ` - Dunes.- I ` '_'» ' ` 1- vs Nfoblle and partlally faxed»_g:.~ I -I. Q Q Payneisgljle Raymond ld. Sou marsh Y 0 > /' B ckw~-{5r Mangroves I s,_ ' * =_,`,' 2»' -f' `» _L_ Fresh water swamp ) / N ' 678 lr/ ~~»_,/'q :`?5? :é9' `>- M f', `>--/ _,1, g 5; _;<5>,» T Alluvlum»'--.-.: r<;7;t!$ '- '` '.3}_53 ;_f=_.$.&;.,._ 4 ao...;_. ecent beach r dges,etc ; ;g, gecent barrler f}ats a terraces. ~-~~ Q 7_ Late Plelstocene deposats » *e > 7 --_» r ) Earluer Plenstocene deposits #_ f ' L-River levees B ~#Sf P' ' Q Sand ridge trends A F/6. 6 SIOP 5.
173 154 Note: _ITI_NERARY Distances are given as miles from Melbourne (a) via South Gippsland Highway to Sale, and (b) thereafter via Princes Highway. The route is divided into a number of major Sections S.l FIRST DAY Melbourne to Five Ways (34 rn. Mainly Upper Miocene terrestrial sediments. S. Z _Efivg W_ays to Nyora _(6Qm. Western Port Sunkland. Quaternary sand dunes and swamp deposits. Tidal inlets with mangroves and salt marsh at Tooradin (39m.) and near Koo-Wee-Rup (44m. Important dairying and market garden area. Rise up Heath Hill scarp as Nyora is approached. S. 3 N yora to Foster (ll41:_n. ' South Gippsland Highlands. Horst and graben topography; mainly Lower Cretaceous arkoses and felspathic mudstones. Black coal near Korumburra. Red soils near Leongatha formed on Lower Tertiary basalt. The Tarwin River Valley is a down-faulted area. Latest earth movements responsible for distinctive topography - late Pliocene to early Pleistocene. S.4 Foster to Toora(122m. Road follows the Gelliondale scarp, the southern limit of the South Gippsland Highlands. Lower Cretaceous sediments north from the scarp except for inlier of Silurian sandstones and mudstones near Foster. Corner Inlet to the south. LOCALITY l - Toora. View from scarp of Gelliondale Monocline. Corner Inlet with Wilson's Promontory (Devonian granite) in the distance. Tidal flats, mangrove fringe and salt marsh, outwash apron extending from scarp. Sandy barrier islands to the southeast. (Centre for dairying industry: note Toora milk products factory). S. 5. Toora to McLaughlin's Beach (l64m. )_, via Taraville. Marine terraces with stranded sandy barriers and intervening swamps (some with thick peat) south of highway. Note mangroves at Taraville - tidal section of Tara River. LOCALITY 2 - McLaughlin's Beach _( _`ig.3p)_: (i) St. Margaret Island - late Pleistocene barrier. (ii) Salt marsh, tidal inlet (Shoal Inlet). (iii) South side of Shoal Inlet - mid-recent barrier - old foredunes with beach ridges extending seawards and stranded tidal flats and salt marsh to landward. Sections of these features along south side of inlet. Mangroves and existing marine fauna. S. 6 McLaughlin s Beach to Sale (l34m. via Princes Highway. Marine terraces with sinuous swamps marking stranded tidal channels. Degraded marine cliff. Rise marking Darriman monocline. Higher level marine terraces with 1 sand barriers (Monkey Creek and north of Stradbroke). Direction of Merriman s Creek probably controlled by depression between the two barriers. Traverse the Baragwanath Anticline with Latrobe Valley Coal Measures brought close to surface. Overlain by Lower Miocene lime stones and marls (pits in creek on north side of road). View across Latrobe Depression to the Eastern Highlands. Descent to Latrobe - Thomson flood plain (levees, back swamps and terrace cut in late Pleistocene alluvial deposits).
174 155 SECOND DAY S. 7 Sale to Lett's Beach - (Golden Beach)_. 0 Glencoe - pits in Lower Miocene limestone, N. dip of 35. Dutson - spring, water supply for several farms. Excellent quality water not of deep-seated origin. Lake Wellington and marginal swamps. Dutson Downs - Sewage farm, domestic and industrial waste from the Latrobe Valley used for irrigation. _L_0 _A_L_ITY;_ 31 - L_gttf_s Beach_. Traverse across the outer barrier to show the Ninety Mile Beach, dune, remnants of earlier barrier, back barrier sandy flat, lagoon, former tidal channels and shell beds. Vegetation zones and relation to land forms. S. 8 L_gt's_1 e _ :_l;1to Q_lydebank. Late Pleistocene alluvial deposits with abandoned stream courses which contain water intermittently - Sale to Clydebank. Dairying, most of area under irrigation. LOCALITY 4 Abandoned levee ridges at Clydebank with intervening swamps and salt and brackish lake s. S. 9 Clyde bank to Payne sville. Avon River occupying silted-up estuary. Levees and backswamps. Rise up old estuary side, then marine terraces, old barrier deposits and dunes, dissected in places, to Paynesville. LOCALITY 5 - Payne sville. Lake Victoria and Newlands Backwater (drowned valley) with sand spit at mouth. Raymond Island and Sperm Whale Head (barrier remnants). LOCALITY 6 _- Eagle Point. Lake King. Silt jetties of the Mitchell River. Sandy facies of Haunted Hill Gravels and overlying Pleistocene (?) gravels exposed in eroding river cliff. S. 10 Eagle Point to Bairnsdale (l77m. Travel along levee of Mitchell River. Back swamps and cliff forming outer margin of Pleistocene terraces on the west. Bairnsdale on late Pleistocene terrace and alluvial deposits. THIRD DAY S. ll Bairnsdal_e tg Sys/an Reach (_1<}0m;2. Bairnsdale to Swan Reach - Pleistocene terraces. Nicholson - Straight reach of Nicholson River. Deeply excavated valley now filled with more than 80 feet of fluviatile and marine deposits. Swan Reach - Straight reach of the Tambo River. Tambo River Formation (Upper Miocene) exposed in road cutting S. E. of bridge. S. 12 Swan Reach to _Lakes Entrance (i99m. Dissected Haunted Hill Gravels terrain. LOCALITY 7 - Lakes Entrance. Note gravels and finer deltaic facies. A..Iemmy's Point - View of the Lakes and Tasman Sea. Note inner cliffed margin of the Lakes; remnants of old barriers (Rigby Island, etc. ); outer barrier cut by artificial entrance.
175 156 B. Jemmy s Point to North Arm - Type section of Jemmy's Point Formation (Lower Pliocene). The North Arm is a drowned valley. C. Old entrance channel - Filling of channel by segmentation due to the formation of cuspate forelands, then migration of U-dunes, taking off from the main foredune. D. Outer barrier and artificial entrance - Main foredune and progradation adjacent to retaining walls. Lunate bar off-shore. Return to Bairnsdale. S. 13 Bair_nsdalg tg tr_atford (_via Lindenow), Ascend and travel along river terraces to Lindenow South. Valley of the Mitchell to the north. Bairnsdale Limestone (Miocene) forms prominent cliffs. Valley widens out upstream from lime stones. Dairying and food crops. Lindenow South to Stratford - Flat (early Pleistocene?) surface with dune and swamp terrain, partly dissected. Nearer Stratford, descend flight of terraces. Note dunes west of Highway near Bengworden turnoff - main camping site of Brayakalung tribe; numerous artifacts, mainly microliths, have been found. Stratford (l45m.) - Severe erosion along Avon River, 3,000 acres lost since 1870's. S. l4 Stratford_to Melbourng Maffra- Traralgon. Milk products factories (Nestles and Mafco) at Maffra - irrigation, dairying to Cowarr - mixed farming to Traralgon. Note prominent scarp of Yallourn Monocline on the west. Traralgon to Morwell - A. P.M. pine plantations. Morwell (94 m.) - Brown coal mining, gas manufacture, briquetting, Hazlewood power house, paper manufacture (mills at Maryvale, N. E. of Morwell). Morwell to Moe (84 m.) - View across Yallournz open cut, briquetting works, power house. Road cuttings showing strongly cross-bedded Haunted Hill Gravels (type area). Cross Haunted Hill fault block. Moe to Yarragon (69 m.) - Moe sunkland, Yarragon Monocline scarp on the south. Yarragon to Picnic Point - Warragul Block, Older Volcanic terrain, mainly dairying. Descend Heath Hill scarp at Picnic Point (56 miles). Picnic Point to Dandenong - Granite country' at about 48 miles; fruit growing Nar-Nar-Goon to Dandenong - tongues of Silurian mudstones and sandstones and Older Volcanics separated by alluvium. Mixed farming, fruit. Western Port Sunkland to the south.
176 157 Bird, E.C.F., Bird, E.C.F., Bird, E.C.F., Boutakoff, N., Carter, A.N., Central Planning Authority, Clifford, H, T., Gloe, C.S., 1960 Hall, T.S., Hart, T.S., Howitt, A.W., Jenkin, J.J., Singleton, F.A., 1941 SELE_CTED REFERENCES The Coastal Barriers of East Gippsland, Australia. Geog. Journ. 127 : The River Deltas of the Gippsland Lakes. Proc; Roy. Soc. Vict. 75 : Note: Information contained in the above, as well as other papers by Bird, will be found in - A Geomorphological Study of the Gippsland Lakes. Australian National University, Research School of Pacific Studies. Dept. of Geog.~ Pub. G. /1 A new approach to petroleum geology and oil possibilities in Gippsland. Mining and G_eol..Tou1j_n. 5 : Tertiary Foraminifera from Gippsland, Victoria and their Stratigraphical Significance. Geol. Surv. Vict., Mem. 28. East Gippsland Region, Resources Survey. Govt. of Victoria. The Mitchell River Delta. Vic. Nat. 65 : 278. The Geology of the Latrobe Valley Coalfield. Proc. A.I,1(_I. M. 194 : Some Notes on the Gippsland Lakes. Vict. Nat. 31 : The Gippsland Lakes Country : Physiographical Features. Ibid. 38 : 75 ' 820 Notes on the geology of part of the Mitchell River Division of the Gippsland Mining District. Geol. Surv. Vict. Rept. Prog. 1 : The Geomorphology and Upper Cainozoic Geology of South-East Gippsland, Victoria. Geol. Surv. Vic., Mem. 27, The Tertiary Geology of Australia. Proc. Roy. Soc. Vicg. 53 : ].'].Z5o Thomas, D.E., and Baragwanath, W., Geology of the Brown Coals of Victoria. Parts 1-4. Mining and Geol. Journ. 3(6) : (1) : 36-52, 4(3) I Turner, J.S., Carr, S.G.M., and Bird, E.C.F., The Dune Succession at Corner Inlet, Victoria. Proc. Roy. S_oc. Vict. 75 : Wilkins, R. W. T., Relationships between the Mitchellian, Cheltenhamian and Kalimnan Stages in the Australian Tertiary. Ibid. 76 :
177 158 CHAPTER 17 GEOLOGY OF EAST GIPPSLAND by John A. Talent INTRODUCTION. The east Gippsland region contains a variety of Palaeozoic sedimentary and volcanic sequences which, particularly in the Tabberabbe ra, Bindi-Omeo-Benambra and Buchan districts, greatly elucidate the Palaeozoic diastrophism of eastern Victoria. The Geological Survey of Victoria 1:63, 360 geological maps Tabberabbera and Cobberas, and Memoir Zl including Buchan sheets, cover much of the critical areas. ORDOV IC IAN. The sedimentary bedrock of eastern Victoria is thought to be Ordovician from regional stratigraphy, although vast tracts have yet to yield palaeontological evidence for this.much of it has been converted to schists and gneisses. These metamorphics form the north-east Victoria metamorphic belt (see Chapter 19). In the Ensay-Omeo-Benambra area they have been referred to as the Omeo Schists and Gneisses. Ordovician sediments, only slightly metamorphosed, occur in three major areas in eastern Victoria separated by the metamorphic belt and the Snowy River Volcanics. These are the broad belt trending NNW from Bruthen to Yarrawonga; the triangular area between Benambra, Mitta Mitta and Corryong; and the area generally east of the Snowy River. Generally these have tightly folded and faulted, monotonous silty quartz sandstones, silstones, claystones and, locally, che rts. They are rarely fossiliferous, and often exhibit slaty cleavage, small scale cross bedding in the coarser units, and flute casts. Their analogues in adjacent N.S. W. are the Adaminaby, Bogong Creek, Boltons and Kiandra Beds or their probable equivalents (Moye, Sharp and Stapleton, 1963). No tuffs or ande sites comparable with those of the Kiandra Beds (Gisbornian) are known. Upper Ordovician graptolites have been listed from isolated localities. Vast areas have yet to yield organic remains, but pre-darriwilian Da4 horizons may be present, as for instance at Tabberabbera; with apparently a descending succession eastwards from the lowest fossiliferous Darriwilian Da4 horizons. As so little graptolite evidence is available, it may be that part of the area of eastern Victoria shown as Ordovician on the Victorian geological map is actually Silurian. However there is a lack of conglomerates, limestones and large sandstone developments, and of the more open folding typical of the Silurian. The fold axes of the Ordovician are to some extent arranged fan-wise, striking approximately NW to NNW in the watersheds of the Mitchell, Wentworth and Nicholson Rivers, more or less N in the watersheds of the Gibbo and Buckwong Rivers, and NNE in the watershed of the Snowy River. The fold pattern is therefore disharmonic with the fan-wise arrangement of the Silurian trending NW along the Mitta Mitta River, NE in the Limestone Creek-Indi River area and progressively easterly eastwards of Bindi. Care is therefore necessary in attributing various tension and shear patterns within the metamorphic belt to a tectonic episode. PRE-MIDDLE SILURIAN GRANITIC BODIES. Granitic pebbles and boulders within the Wombat Creek Group are clear evidence for pre- Middle Silurian granitic intrusion in eastern Victoria. It is however difficult to discriminate any such bodies from younger intrusions for the area has had repeated plutonism and diastrophism. Nevertheless intrusive sequences can be inferred (Crohn, 1950; Beavis, 1962), and a pre-middle Silurian age may be inferred for the Banimboola Granodiorite which, with its associated metamorphic belt, outcrops in the watershed of the Mitta Mitta River upstream from Mitta Mitta._ The Mitta Mitta Volcanics in this area are pre-wombat Creek Group (see below) and therefore predate some time in the Middle Silurian. Road sections along the Mitta Mitta River north of Eustace Creek show Mitta Mitta Volcanics intrusive around huge, sometimes house-sized, blocks of granodiorite, and thus post-dating
178 159 the Banimboola Granodiorite, which likewise pre-dates sometime in the Middle Silurian. Intrusions often gneissic, concordant with the Omeo Schists and Gneisses such as the Mt. Wills muscovite granite and the various granitic bodies along the Tambo valley from Tongio Gap to Ensay appear to be epi-ordovician, discordant bodies such as the Knocker red granite are clearly younger, probably much younger. SILUR IAN. Broadly the re are two differing tectonic and sedimentary provinces in the Silurian and Lower Devonian of Victoria: the Eastern Victorian Province where the Benambran and Bowning deformations and associated igneous activity left a profound imprint, and the Central Victorian Province where the effects of these deformations are not so clear and where vast tracts of poorly fossilife rous basin sediments formerly prevented extended unravelling of stratigraphic relationships. The tectonic and sedimentary history of eastern Victoria is the more complex and, in many respects contrasts with that of central Victoria, particularly during the Silurian, though some connection between the two in Lower Devonian times is evident from the sequences at Waratah Bay and on the Mitchell and Wentworth Rivers. Silurian sediments outcrop in eastern Victoria principally about the headwaters of the lndi, Tambo, and Buchan Rivers. A restricted development, the Wombat Creek Group, outcrops about the junction of the Gibbo and Mitta Mitta Rivers, and is associated with an attenuated belt of Silurian Volcanics - the Mitta Mitta Volcanics. After being originally regarded as Silurian, the Wombat Creek Group was thought to contain both Silurian and Middle Devonian faunas (Chapman 1920), but re-inve stigation (Talent l959a; Singleton & Talent MS.) has revealed that the entire sequence is Silurian. The Mitta Mitta Volcanics forma me ridional beltfrom the headwaters of Tallangatta Ck. to the junction of the Gibbo and Mitta Mitta Rivers, and underlie the Wombat Creek Group (Singleton, 1965). They broadly resemble the Snowy River Volcanics with rhyodacites, often highly fragment al, subordinate rhyolites, tuff, and minor sediments, generally tuffaceous. Ascending the Mitta Mitta River from its junction with the Gibbo River, successively higher horizons of the Wombat Creek Group are traversed (Talent, l965b), until the sequence is truncated by a SE-trending fault. The Wombat Creek Group commences with a basal sequence of over 1, 000 ft. of conglomerates containing occasional pebbles and boulders of Mitta Mitta Volcanics (Singleton, 1965); rare fossil horizons include, inter alia, trimerellid brachiopods. This is ove rlain directly, or with minor intervening sandstones, by a prominent limestone 300 ft. or more thick. The limestones and associated fossiliferous shales have yielded a moderately rich fauna including species of Mucophyllum, Propora, and Brachyprion and are ove rlain by probably more than 1, 500 ft. of generally fine-grained terrigenous sediments,with a minor conglomerate on the Mitta Mitta River (Whitelaw, 1954, Fig. ZE) having occasional granitic boulders. This sequence is overlain by a limestone (Whitelaw 1954, Fig. ZF and ZG) containing, inter alia, halysitid corals; approximately the same horizon with poorly preserved halysitids and brachiopods outcrops in allotment 9, Parish of Hinnomungie (Whitelaw 1954, Fig. 3D) at 'Pyle's lime stone deposit'. The Wombat Creek Group is terminated by sandstones and siltstones downthrown against Upper Ordovician graptolite-bearing sediments which pass to the south and west into the Omeo Schists and Gneisses. There is a remarkable contrast in tectonic style between the highly deformed, tightly folded Ordovician sediments and the fairly steeply dipping though not tightly folded Wombat Creek Group. The vast outpourings of Mitta Mitta Volcanics, many thousands of feet in thickness, and the enormous thickness of basal conglomerates of the Wombat Creek Group, indicates appreciable tectonic activity and, it would seem, strong folding of the Ordovician basement in Lower Silurian times (the Benambran Orogeny). The presence of granite pebbles and boulders within the Wombat Creek Group is clear evidence for pre-wombat Creek Group grariites. Silurian sediments (the Cowombat Group) outcrop extensively about the headwaters of the Indi, Buchan, and Tambo Rivers, and are overlain unconformably by Snowy River Volcanics. The lowest unit, the Towanga Formation, consists of generally fine sandstones or quartzites, seemingly exceeding. 10, 000 ft., with subordinate siltstones and lenticular lime stones, the Caladenia and Farquhar limestone members. Higher in the Towanga Formation are lenticular
179 ~ Alluvium; swamp deposits f-' era ~ Basalt CEJ Syenite porphyry ~ Syenite [KJ Granite porphyry IT] Trachyte r::z;j Mount Tambo Group C2'J Snowy River Volcanics ~ Silurian J±]3 Marengo Granite ::±J Grey granite and granodiorite B Upper Ordovician - slates t schists. etc. 0 i 1 i Miles ~, ' ~ --' ':' Yo. O«'~,~ 'f',o{,1-':..- / j~s~ts~»a -~'~'I 1 / Fig. 1. Geology of the Bcnambra -.,1t. Lcinstcr area (based on mapping by F.. Broadhurst, J.D. Campbell, p.1t-/. Crohn and J.A. Talent).... ~ ~ ~
180 161 conglomerates outcropping principally at Mt. Carabungla (the Carabungla Member) and on the lndi River between Copperhead and Bullies Creek. Southwestward toward Bindi, conglomerates dominate an appreciable thickness of the succession (the Mt. Waterson Formation) and overlie the largest limestone in the Cowombat Group, the Qld Hut Limestone. Stratigraphically higher than the Towanga Formation is the Cowombat Formation, composed typically of richly fossiliferous late Wenlock - early Ludlow siltstones and minor limestones at Cowombat and Native Dog plains, dominated by species of Mucophyllum, Mazaphyllum, Fletcheria, Favosites, Heliolites, and Propora, with rare Atrypoidea, Atrypa, and Howellella. Farther we st are numerous lenticular limestones, the largest being given separate member status: the Sheehan Bluff, Claire Creek, and McCarty Members. The Cowombat Formation is terminated by unfossiliferous siltstones followed by at least 1, 000 ft. of unfossiliferous fine-grained sandstones. No Silurian volcanic rocks have been discriminated within the Cowombat Group though such may occur among the fault slices between Bindi and the headwaters of Limestone Creek. The Cowombat Group has been intruded by the Kosciusko Granodiorite, one long tongue dividing the two main outcrop belts of Towanga Formation. As the Cowombat Group contains faunal equivalents of the Bowspring Limestone and the Barrandella Shale and still younger unfossiliferous horizons, its earliest deformation can scarcely precede the top of the Silurian. Yet deformation had taken place, followed by intrusion of granodiorite and extensive unroofing of the batholith, before deposition of the Timbarra Formation (5, 000+ ft.), followed by extrusion of the Snowy River Volcanics, with many hiatuses, prior to deposition of the late Emsian or early Eifelian Buchan Caves Lime stone. Silurian sediments have been found sub-surface beneath the Snowy River Volcanics in the parish of Nowa Nowa South, south of Buchan and outcrop in a little known belt between Martin s Creek and the head of Sardine Creek. These occurrences, together with the Cowombat and Wombat Creek Groups, indicate basin sedimentation, presumably in different parts of the same basin. Analogous thick sequences of Silurian sediments are found farther north in New South Wales, in particular in the Yarangobilly-Ravine-Turnut Pond area. This contrasts to some extent with that at Quidong, about 12 miles west of Bombala, where richly fossiliferous limestones and associated shales, correlating broadly with the Cowombat Formation, indicate more shelf-like conditions. In contrast, in central Victoria, Lower Silurian (Llandovery) graptolitic sediments, seemingly conformable with Ordovician occur on the Maribyrnong River, at Warrandyte, Diamond Creek, Macclesfield, Enoch s Point, and on the Dolodrook River. For younger horizons there is an expanding gap in palaeontological knowledge going eastwards, the lowest fossilife rous post-llandovery beds becoming younger (Fig. 1). This gap may be connected with the breaks in sedimentation to be expected from an eastward increase in intensity of deformation associated with the Benambran and later movements, approximating the Bowning deformation,in eastern Victoria. DEVONIAN. The deformation at the end _of the Silurian or commencement of the Lower Devonian was followed by the intrusion and de-roofing of the Kosciusko Batholith. Thick sequences of nonmarine conglomerates, sandstones and siltstones, and minor ignimbrites, at least 5,000 ft. in thickness, the Timbarra Formation, were deposited between Buchan and Black Mountain (Fletcher 1963, E.A. Woodford pers. comm.). Subsequently the Snowy River Volcanics complex of more than 10,000 ft. of rhyodacites and tuffs, with subordinate rhyolites, andesites, keratophyres, and basalts accumulated over a large area east of the Tambo River. Evidence from Bindi, best seen at Mt. Waterson, shows that the Snowy River Volcanics and the underlying Cowombat Group were block faulted and planated prior to deposition of the Buchan Group. Other parts of the Snowy River Volcanics belt appear block faulted prior to deposition of the Buchan Group, most notably the belt from Nowa Nowa through Mt. McLeod to the vicinity of Butchers Ck., where a jig-saw of blocks of Ordovician sediments and pre-devonian granite is interrupted by a cover of Buchan Group sediments which are, by comparison, little disturbed. Post-Middle Devonian tear faulting and thrusting on this same belt has been much less severe than that which must have occurred before deposition of the Buchan Group.
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182 163 Subsidence of the more or less planar Buchan-lndi-Combienbar area led to deposition of the remarkably uniform Buchan Caves Limestone cove ring at least Z, 500 square miles. This is now represented by a series of some 14 discrete, tectonically preserved, enclaves commencing typically with a basal sequence of dolomites (the Spring Creek Member), exceeding 200 ft., in the south-east at South Buchan, but thinner in the west at Bindi and in the three enclaves along Lime stone Creek. The Buchan Caves Limestone is overlain by the Taravale Formation which, in turn, is in facies relationship with the Murrindal Lime ston-e. A prominent tongue of Taravale Formation, the Pyramids Member, separates the Murrindal and Buchan CavesLime stones in the Buchan-Murrindal area. Faunas typical of the Pyramids Member at Buchan occur at the top of the Buchan Caves Limestone at Bindi. The presence of Adolfia in abundance and the bizarre ostracode genus Poloniella, of Calceola sandalina, Nadiastrophia n. sp., and Aulacella indicate an Eifelian or ' possibly late Emsian horizon, in agreement with goniatite faunas occurring in the first 600 ft. or so of the Taravale Formation at Buchan. Higher in the sequence, in the Murrindal Limestone, a further species of Calceola (a tiny one), a new genus resembling Leptodontellaj, C_yrtinogig, a new genus of rhynchonellid to include the Eifelian Hypothyridina proc_uboides, and a variety of new genera of rhynchonellids of Eifelian aspect occur. The great thickness of poorly fossilife rous Taravale Formation at Buchan (Z, 500+ ft.) and at Bindi (3, 500+ ft.) indicates the possibility of the Buchan Groupascending even into the Givetian. The Devonian succession on the Mitchell and Wentworth Rivers (Talent, 1963) rests with marked angular unconformity on folded Upper Ordovician sediments without the intervention of a Silurian sequence to help discriminate between Benambran and Bowning deformation. The lowest fossiliferous unit, the Wild Horse Formation, contains a poorly preserved and essentially unde scribed fauna recalling that of the Coopers Creek Formation, indicatingpithat the wide' accumulation of lime stones and conglomerates about the base of the Walhalla Group was contemporaneous with thick marine deposition of essentially terrigenous sediments at Tabberabbera. This contrasts with the contemporaneous subsidence and deposition of the Waratah Limestone unconformably over Cambrian greenstones at Waratah Bay. Higher in the succession within the Kilgower Member at Warrigal Bend, Sandys Creek, and at Tabberabera (Loc. 35), there occur faunas of Lower Emsian aspect,more or less equivalent to horizons 1-2,000 ft. above the base of the Walhalla Group. The Wentworth Group was rather strongly folded and intruded by the Tabbe rabbe ra Dyke ' Swarm and the re had been extensive planation prior to deposition of the comparatively flatlying non-marine Avon River Group sediments with interbedded lavas. This Tabberabberan Crogeny affected all Lower to Middle Devonian sediments in Victoria. Associated large scale faulting, is in part along pre-existing fault lines, e. g. the East Buchan Thrust and its associated belt of deformation follows a pre-buchan Group fault belt affecting blocks of Snowy River Volcanics, Ordovician sediments, and pre-devonian granitic rocks. Movement occurred along some of the largest faults in eastern Victoria at this time, though in most the absence of adjacent Upper Palaeozoic sediments prevents discrimination of post-tabberabberan movements, with the notable exception of the lndi Fault. UPPER DEVONLAN. Deformation of the Lower to early Middle Devonian sequences of Victoria took place principally between the Eifelian and some tinie early in the Upper Devonian (Tabberabberan Crogeny). Syntectonic dyke swarms, notably the Woods Point and Tabberabbe ra swarms, were followed by post-orogenic intrusions of granitic batholiths in central Victoria, with a few in eastern and possiblyin north-eastern Victoria. The pattern of plutonism, volcanism and sedimentation in Victoria during Upper Devonian times is complex. Broadly speaking three provinces can be discriminated: a western province with a basal sequence of rhyolitic lavas, pyroclastics and trachytes succeeded by a thick sequence of late Devonian to possibly early Carboniferous terrigenous sediments; a central province with minor development of terrigenous sediments, but characterised by vast outpourings of predominantly acid lavas in part connected with cauldron collapses and intruded by the parent intrusions; and an eastern province where te rrigenous sedimentation again predominates over rhyolitic and basaltic Volcanism.
183 164 In the watersheds of the Macalister, Avon and Mitchell Rivers volcanics are subordinate to terrigenous sediments. The Avon River Group (Neilson, 1964 ; pers.comm.) consists of about 4, 600 ft. of non-marine conglomerates, sandstones and mudstones with interbedded rhyolites (the Wellington Rhyolites) and minor tuffs and basalts. The rhyolites thin eastwards disappearing some distance east of the Mitchell River (Talent, 1963). Fish remains from associated sediments have confirmed a late Devonian age for at least part of the A.von River Group (Hills, 1931); plant remains seem to indicate that the higher beds of this group are.late Devonian. These rocks are broadly folded, their distribution in the Avon and Macalister watersheds being determined by two bounding faults. The Mt. Tambo Group outcropping in a belt extending from Mt. Bung through Mt.- Tambo to Mt. Shanahan near Bindi,consists of 10, 000 ft. or more of well bedded reddish and purplish shales and sandstones, with conglomerates up to 40 ft. thick. The sandstones and coarser sediments are poorly sorted, the grains are often angular, cross bedding is common. Arkoses are not infrequent, as for example at Mt. Shanahan. A single rhyolite flow contrasts with Upper Devonian sequences to the we st. The Group is analogous to Upper Devonian sequences to the east and we st, no adequate plant remains or fish plates have been found.; The Mt. Tambo Group is unconformable to the Omeo Schists and Gneisses to the east; on the west it has been intruded by The Sisters Granite Porphyry, though farther south the boundary is faulted. It is faulted against the Snowy River Volcanics and Buchan Group to the south-east on a continuation of the Indi Fault. Conglome rates, silty sandstones and sandy siltstones at Mt. Waterson, formerly placed in the Mt. Tambo Group, have recently (Talent l965b) been shown to be Silurian (Cowombat Group) and to unconformably underlie the Buchan Group. TRIASSIC. The landscape about Benambra is dominated by inselbergs and rugged hills of syenite and trachyte,together with more subdued hills of granite porphyry. The granite porphyries and syenites with transitional types, have been grouped as one igneous cycle (Crohn 1950). Evidence from a number of localities, such as Mt. Little Tambo, sugge sts that granite prophyries and syenites have intruded thetrachytes. The trachytes associated with these complexes are diverse in texture and predominantly porphyritic; both flows and pyroclastics are present. The rocks mapped as syenite in the Benambra - Mt. Leinster district include porphyritic and even-grained varieties ranging in com-' position from soda syenite to soda granite. Metamorphic aureoles of hornfels 5 to 10 chains wide formed in surrounding Ordovician low grade schists. At Mt. Leinster is ap contact between syenite and granodiorite of the Marengo Granite, with potash metasomatism from the former to the latter (Broadhurst and Campbell, 1933). The syenites and associated intrusions were formerly regarded as late Devonain or early Carbonife rous in age, but a K/Ar date has shown them to be of late Triassic age. CAINOZOIC. Cainozoic Volcanics and sediments and the complex tectonic history have affected the physiography. Three main residuals of Tertiary basalts occur, sometimes grouped with the Newer Basalts. The presence of the Cinnamomum flora in association with the Gelantipy- Wulgulmerang basalts confirms an early Tertiary age and would suggest a similar age for the Nunnet-Nunniong basalts which occur in a similar geomorphic setting. The Morass Creekbasalts north of Benambra lack known eruption points (those formerly adduced are inliers of Silurian bedrock) and are on an old surface being reduced by Morass Creek and the Gibbo and Mitta Mitta Rivers. Scattered outliers indicate that these basalts formerly occupied at least two or three times their present extent, extending down the Mitta Mitta gorge and for some distance up the valley of Wombat Creek. They appear to be early Tertiary. Lunettes and alluvial sediments about Benambra are noted under Locality 1.
184 165 AC <g_ 5' 5 6 -Q 5- 6 Q,glég N5 7 `. Le L Q wo 1 '* U 4.1 ' gs Q?) 4 Q/ -47 ' tmt. Cobberas No.1 4 'LJ _*' B S 10 r 3 urnbra 11 a R- 1 lver & L.0m o W# 6;»,> 2, C Q 13 ogre 4 R. bl. eo xi Wulgu merang Q? '59I O Q gteniong mé& 9.2 _XY v' Q, ` wift's Creek ~'~ 1 u ela tip 32 Q, Q5,_, 6 'Q 0 H 2 1 ~ O E 'u' 1 AMt. Baldhead &*' nsay ~ 1 In 31 5 ~ / 91 A? 4» <3 8 Q;- ~? '5 ( n Y ng. O s~o 3 9 r) I C - M E <9 '7'` ~ g wth# b»erabbe?é_ 38' I Pvi. ullurnwaal. Q* _AW Q? 'go '54. < '$ U _ 4. &» ruthen INDWI Phnva 3* Mitche1L-RĪver i 2 =a1rnsd» -, / 0 MILES 8 ea,/ Fig. 3. Position of localities in itinerary.
185 166 ITINERARY FIRST DAY LOCALIT_Y 1 Bepambra. Starting from the dry lake-bed of Lake Omeo, transport is desirable. and travelling eastwards, four-wheel drive The Benambra - Lake Omeo district forms an intermontane basin drained by tributaries of the Mitta Mitta River. The drainage patterns in the Omeo-Benambra district display a number of pronounced elbows and boat-hook bends which, when considered in conjunction with the number of low saddles, indicate a complex history of stream capture. Previous authors have concluded that the Big River, Gibbo River and Morass Creek originally flowed southwards into the Tambo River and were captured by the headwaters of an ancestral Mitta Mitta River. The picture is complicated by differential erosion features and a _complex Cainozoic tectonic history which is yet to be fully deciphered. The terrain some l5 miles eastwards from Benambra is dominated by inselbergs of syenites and porphyritic syenites, e.g. McFarlane's Lookout, Pende rgast's Lookout and Mt. Leinster. Comparatively recent fault movements can be exemplified by the Buenbar Fault responsible for the formation of broad alluvial flats along Benambra Creek and along the Indi River at Tom Groggin, upstream from the Murray Gates. The town of Benambra is on a narrow horst separating the flats about Lake Omeo from the alluvial flats along Morass Creek immediately east of Benambra. It is uncertain whether the alluviation along Morass Creek is connected with a series of basalt flows extending northwards from Uplands to Frazer's Tableland and beyond, or whether it is to be attributed to tilting. The Mitta Mitta River was antecedent to uplift of the main Toak's Gibbo horst on the north side of the Gibbo River, but movements along this horst terminated before the outpourings of Cainozoic basalts because portions of the old basalt-filled valley can be traced down into the gorge; the surface levels have not been disturbed. Lake Omeo is bordered on the south by a well developed lunette, bordered in turn by a complex of swamp deposits. The lake margins display a well developed series of benches, with one particularly large one on the north side. The area was notable for some early finds of diprotodonts. - LOCALITY 2 - Pyle Lg limestone. Py1e's lime stone deposit 3 m. north-east of Benambra, is the former site of a lime kiln. Here fossiliferous Silurian sandstones, mudstones and calcareous sediments have been intruded by the syenites with consequent metamorphism, and the introduction of minor amounts of pyrite, galena and chalcopyrite. Outcrops are poor, leaving some uncertainty as to the relationship of these sediments to surrounding trachytic and syenitic rocks. Whitelaw (1954) regarded the trachytic rocks as overlying the sedimentary sequence but Crohn (1950) concluded they were inte rbedded and that the limestone deposit was a replacement body. Fossils within these metamorphosed rocks are by no means common, but include poorly preserved Howellella, halysitids (?Catenipora) and solitary rugose corals. Large boulders of soda syenite from The Brothers intrusion, including both porphyritic and even-grained types, occur upslope from Pyle's deposit. ; _R.g.N ;'r. Return to Benambra, and then head eastward along the south side of the Morass Creek flats with the imposing mass of Mt, Tambo on the right, flanked on its eastern side by the more subdued topography of The Sisters granite _porphyry intrusion. Mt. Tambo is part of a belt of non-marine reddish and purplish sandstones, conglomerates and subordinate shales (the Mt.,Tambo Group). dipping steeply we stwards. Basal beds consist of conglomerates containing a thin interbedded flow of rhyolite about 30 ft. thick. No dete rminable fossils have yet been found, an Upper Devonian age being attributed on grounds of close lithological similarity to Upper Devonian sediments elsewhere in Victoria. It is
186 generally assumed that the granite porphyries of the area are intimately connected with intrusion of the syenites for there are transitional types between the two series. The steeply dipping to near vertical attitude of the entire body of the Mt. Tambo Formation extending from Mt. Tambo to Mt. Shanahan at Bindi is indicative of significant post-upper Devonian pre-upper Triassic epeirogenesis or orogenesis in this area. LOCALLITY 3 IN - Porphyry int_rl_lsiv e_. Road cutting l m. south of Marengo Gap. Typical exposure of one of the larger masses of granite porphyry associated with the syenites and therefore assumed to be of Triassic age. The particular intrusive mass includes quartz-felspar porphyries, rocks transitional to syenite as well as a chilled border phase Z or 3 chains in width with darker colour and finer grain size. The dominant rock types are porphyritic and tend to be more sodic than The Siste rs intrusion. TRANSIT. Proceed east over belts of Ordovician sediments and granitic rocks, by-passing the Mt. Leinster syenite-trachyte complex (Fig. 1). The Indi Fault system separating Ordovician sediments and low grade metamorphics from the Silurian and Devonian succession to the east is not well exposed on the Tin Mine Road. LOCALITY 4. On the descent to Limestone Creek argillaceous sediments typical of the upper units of the Co Wombat Formation occur. Exposures along Limestone Creek are in general poor; a better strati graphic sequence is exposed along Stony Creek but the quality of the fossils is poor. Note the westerly dip of the 'Snowy River Volcanics north of Stony Creek, and the small enclaves of Buchan Caves Limestone hooked in against the Indi Fault. The se are virtually identical in lithological and faunal succession with the lower part of the sameformation at Buchan and elsewhere. L_O J_ llit_ _= -_ Cowombat Plain. Richly fossiliferous lime stone and argillaceous sediments on the Victorian side of the border The same general horizon outcrops northwards along the strike across Cowombat Creek (or the Indi River) onto the slopes on the N. S. W. side of the creek. LocAL1TY `6. A larger lenticular body of limestone capped unconformably by an outlier of Snowy River Volcanics extends across the ridge to the north of Cowombat Plain outcropping strongly on the south side of Marble Creek where the unconformity can be readily appreciated. Fossils from the belt of fossiliferous sediments at Cowombat Plain include Fletcheria dendroidea in great abundance, Heliolites daintreei, Mucophyllum crateroides, _Mg liliiforme (rare), a number of species of Favosites including _F_. allani and_f_= walkomi, species of Catenipora, Aulopora, Syringapora, Alveolites, Plasmopora, Propora and Mazaphyllum. Brachiopods, comparatively rare, include Atrypoidea australis and species of Coelospira, Atrypa and Protatrypa. LOCALIT Y 7. Unconformity between Snowy River Volcanics and Cowombat Group along the Tin Mine Road near Copperhead Creek. Near ve rtical Cowombat Group sediments are overlain by near horizontal volcanics charged with blocks of diverse lithology including rounded stream? boulders- in a rhyodacite matrix; block size decreases upwards. The surface of the Silurian rocks shows baking close to the contact. The road section is a graphic expression of an incandescent tuff flow charged with b_locks of other flows, stream deposits and nonvolcanic country rocks picked up during eruption.
187 168 SECCND DAY LOCALITY 8 -Native Dogg gplai1_g_. Richly fossiliferous Silurian shales ove rlain by blue-grey fossiliferous limestone approximately equivalent stratigraphically to the fossiliferous horizons at Cowombat Plain (Loc. 6). The fauna is generally similar to that at Cowombat with the addition of a compound form of Mazaphyllum and a small species of Howellella. The plain is the focus of a number of faults, which have produced, inter alia, contorted marbles at a number of localities. LocAL1TY 9. Enclave of Silurian sediments up-faulted among Snowy River Volcanics in the watershed of Bough Yard Creek, beside the Wombargo jeep track, east of Native Dog Plain. Occasional sink holes, such as one beside the track, reveal the pre sence of carbonate rocks. LOCALITY 10. Pleist%cene block streams on the NNW flank of Mt. Wombargo. These typically slope at about 26, are up to 600 yards in length, as much as 50 yards or more in width, and are composed of blocks of rhyodacite usually 6 in. to Z ft. in length with some blocks up_to several tons in weight. Each blockstream is associated with a seepage or has an appreciable flow of water issuing from its foot; rarely is there any evidence of surface flow of water on a rock river and whe re there is it is ve ry localized and in no way alters the impression of all drainage being beneath the boulder accumulation. The rock rivers themselves have the rough morphology of surface drainage, being joined in small measure by tributaries and having a tendency to disintegrate towards their head into a series of feeders. The surfaces of the boulders are fractured and fretted; the quartz phenocrysts now project above the surfaces of the boulders. The undisturbed growth of trees occurring often in midstream and the apparent lateral extension of the same material into completely vegetated areas on either side reinforces this picture of complete immobility under pre sent climatic conditions. It seems they have been at a standstill for a long time, in view of the appreciable advance of soil and vegetation. The very great thickness of these rocks and the great amount of open space is incompatible with generation in situ. The size and rnorpholcgy of the boulders is against derivation from pre-glacial weathering mantles. Most significant are that the morphology resembles a stream, running water occurs beneath each rock river, and they originate in many cases at a series of low bluffs, indicating that the blocks were derived from the bluffs whe re, presumably, they were wedged out by vigorous frost action. The massive rhyodacite, impervious except along well spaced joint planes, was eminently suitable as a source of large blocks. They were most probably moved downslope from the bluffs by frost heave, becoming gradually incorporated in a rock 'glacier' with its interstices filled with ice from water from the subjacent spring. In their lack of interstitial filling these rock rivers are similar to the rock glaciers described from Alaska where, too, the interstitial filling, if present at all, consists only of ice. The 26 slope of the Wombargo and Big Hill rock rivers is rather higher than the slope of the Alaska rock glaciers. Unlike the Alaskan rock glaciers, they do not seem to have been the dying stages of a glaciation but rather the climax of periglaciation reached at this locality. Had they been connected with the dying stage of glaciation there should be a few cirques and moraines in the area. A fuller account of this and related phenomena is given by Talent (l965a). LOCALITY ll. Mylonitized Marengo Granodiorite associated with the Indi Fault on the Tin Pot Creek jeep track, about a mile west of the Nunniong Track. Minor gold mineralization occurs in this belt; low grade tin (cassiterite) mineralization occurs in the Marengo Granite. Similar mylonitization is developed elsewhere along the lndi Fault where it has intersected granitic and higher grade metamorphic rocks; mylonitization is less spectacular whe re it intersects Ordovician and Silurian sediments.
188 169 LQCALIT Y 12. Faulted Snowy River Volcanics and Silurian sediments about Clove ry Flat (head of Bentley Ck.); fault breccia. Loc./.i,1TY 13. Mt. Carrabungla or The Rocks'. Typical development of Silurian conglomerates composed of well rounded boulders of reef quartz, quartzite, sandstones and chert, within the Towanga Formation. The unit wedges out to the northeast and Southwe st. More spectacular developments of conglomerates occur at Mt. Waterson, Bindi, and in the Silurian succession at Wombat Creek. LOCALIT Y 14. Horse Flat on Reedy River - Tambo River divide; an outlier of early Tertiary basalt uplifted relative to the main developments in the Emu Plains- Nunniong - Nunnet area to the south. The Reedy River Fault separating Silurian from Crdovician sediments is located near the southern end of the outlier; it corresponds here to an abrupt change from essentially unmetamorphosed sediments to phyllites and low grade schists. 1_.ocAL1TY 15. Diggers Holes jeep track on the north flank of the Mt. Nunniong - rare poorly preserved Upper Ordovician graptolites in hornfels among schists in the aureole of the 'Timbarra Granite', an extension of the Kosciusko Batholith. LOCALIT Y 16. Nunniong Plains - a complex of upland swamps and plains developed predominantly on Tertiary basalts and to a lesser degree on granitic rocks. The basalts are markedly stepped, some of the_ stepping at least being correlated with different flows of basalt and the presence of sediments (including 'quartzites') between flows. An early Tertiary age is attributed by analogy to the Gelantipy-Wulgulme rang basalts; these have yielded a lower Tertiary flora from the associated pre-basaltic sediments. THIRD DAY The excursion will proceed via Timbarra Plains, a series of up-land herb fields developed on granitic rocks along the headwaters of the Timbarra River, and Nunnet Plains, another basaltic high plain analogous to Nunniong Plains, to Mt. Johnson, west of Buchan. LOCALITY Mt. Johnson fire tower_. The upper of two flows of ignimbrite forming the top of the Johnson Member of the Timbarra Formation. LOCALITY Mt. Johnson Road west of Mt. Johnson. Finely bedded siltstones of the Johnson Member which have yielded *rare plant remains. LOCALITY Conglomerates of the Lower Timbarra Formation outcropping on the Wilkinson Track. Such conglomerates bulk large within the Timbarra Formation in its two most important developments, viz. west of Buchan and west of Wulgulmerang. The precise thickness of the formation cannot be determined for west of Buchan it is faulted down against Ordovician rocks and it is faulted against Snowy River Volcanics to the east. The same formation is unconformable on late st Silurian or earliest Devonian granodiorites intruding Cowombat Group sediments west of Wulgulmerang. The Timbarra Fgrmatign contrasts with the overlying Snowy River Volcanics in the very subordinate nature of volcanism, and the dorninance of coarse-grained clastic sedimentation.
189 170 LOCALITY 20. The South Buchan area is covered by Lower Tertiary basalts ove rlain in part by a veneer of Tertiary sands and gravels. The relationships were revealed in a road`cutting flanking Allotment 15F made about 1961, but the exposures have now deteriorated. LOCALIT Y 21. Neptunian dykes intersecting Tertiary clayey and gravelly sands in road cuttings near the junction of the Gillingal and Bruthen roads. LOCALITY 22. The Buchan basin may be entered from the south, descending past a series of road cuttings in poorly fossilife rous claystones, shales and nodular argillaceous limestones of the Taravale Formation; these occupy the centre of the Buchan Synclinorium. The youngest beds of this formation are the youngest marine Palaeozoic sediments in eastern Victoria with the possible exception of the highest beds of the same unit at Bindi which may extend to younger horizons. _LOCALITY 23. Fairy Beds exposed in trenches on the south side of Spring Creek west of the Caves Reserve. The trenches show agglomerate overlain by siltstones with two horizons of calcareous nodules containing a non-marine fauna of ostracods, conchostracans, gastropods (?pulmonates) and fish remains, the latter being described by Dr. J.W. Warren (1967 ANZAAS summary papers). This non-marine interval is terminated by tuffs and fragmental rhyodacites, the latter being overlain with near conformity by the Buchan Group. LOCALITY 24. Dolomites characteristic of the lower part of the Buchan Caves Limestone on ridge between Fairy and Spring creeks. Elsewhere in the area there are intercalations of reworked tuffs, mixed carbonate and pyroclastic sediments, earlier interpretedas transitional between Snowy River Volcanics and Buchan Group; however the latter is regionally unconformable over a previously block-faulted and eroded terrain. It re sts on various horizons of the volcanic sequence, as well as directly over the Silurian Cowombat Group at Bindi where block faulting is in evidence. Although the volcanic horizons are lenticular (Fletcher, 1963), this is ' insufficient to explain the overlap of the Buchan Group and the regional unconformity. LOCALITY 25. Faulting within the Buchan Group in the vicinity of the Moon and Federal caves is displayed graphically by a belt of Taravale Formation along the fault and repetitionof the upper part of the Buchan Caves Lime stone. LOCALITY (Loc. 209, Parish of Buchan). Exposure of high Buchan Caves Limestone in the bed of Spring Creek showing crosssections of large nautiloids. Prominent fossils include _S_pinella buchanefnsis Buchanathyris we stoni, _Chalcidophyllum r_gce_s sum. LOCALITY lq_o 'Lardsinsi_c_1e_entr_ance _t_o_ Caves E_ _e serve. Typical exposures of lower Taravale Formation shales, argillaceous limestones and calcareous mudstones with rather rare but well preserved brachiopods, corals and nautiloids, generally fragmental goniatites, and poorly preserved gastropods. Fossils include the goniatites Tei_ch_er1;iceras desifzleraturn, Talenticeras talenti, _Lobobactrites inopinatus, Bactrites sp. and species of Lissatrypa, Atrypa s.l., Qleistopora, Chponetggs, Qarachonetes (rare), Buchanathyris, Spinella (rare), Thamnopora, _Pectinocer_a_s, _Macrod9mp,_c_eras, Phacops (rare).
190 171 Other features include the rather complex tectonics about the East Buchan Thrust, the limonite bodies in the Buchan Caves Limestone south-east of Buchan, and the lead mines at Back Creek and along the Murrindal River. LOCALIT Y 2 8. Proceed north along the Gelantipy road past about 5 rniles of road cuttings in Taravale Formation to the Rocky Camp area, including a traverse east from Rocky Camp (localities 142, 144, , Parish of Buchan) In this area a second lime stone formation, the Murrindal Lime stone, overlies a tongue of Taravale Formation, the Pyramids Member, and fades out southwards into the latter with increase of argillaceous inte rcalations. Well bedded dark grey lime stones with occasional intercalations of argillaceous sediments and occasional silicified horizons pass upwards into paler grey massive to poorly bedded lime stones with an abundance of tabulate corals (Favosijces, Thamnopora, Alveolites), stromatoporoids, rugose corals (principally X_y ;riphyllurn rnitchelli), brachiopods (particularly Cymostrophia, Adolfia and some new genera of rhynchonellids) and trilobites (Cvravicalymene, _ cutellum and a proetid). It has been suggested by Dr. C. Teichert that these more massive limestones constitute a reef facies, but, despite some evidence of frame building, the large amount of detritus and the lack of appreciable solid nuclei in these areas would seem to discount this theory. (Loc. 235, Parish of Buchan). Intercalations of argillaceous and calcareo-argillaceous sediments within the lower Murrindal Limestone. LOCA_L_ITY_ LOCALITY Road cutting north of Murrindal State School. Basaltic sill within the upper Buchan Caves Limestone intruded over an anticline. Grain size ranges from coarse dolerite (micro-gabbro) in the centre of the intrusion to fine-grained basalt in the border phase; the re is minor contact metamorphism of the limestones. LOCALITY 31. Proceed past bedded tuffs, and massive rhyodacites about the W Tree Creek Bridge, over Tertiary basalts and small outliers of Buchan Cave Limestone to Butchers Creek; thence westwards, descending from the Snowy River Volcanics belt to the underlying 'Timbarra Granite', crossing the Buchan River at 'Fanwick', an abandoned farm. LocA,L1TY 32. Return via Mellock Mungie to the Nunnet Road and thence back to Nunniong Plains. FOURTH DAY LOCALIT Y 3 3. Proceed westwards to pass via Emu Plains along the Bindi track across a belt of metamorphics and down a very steep descent to a saddle about 4 miles we st of Nunniong Plains; the track then follows a strike ridge of Snowy River Volcanics for about % mile. The low saddle coincides with the crush zone of the Bindi Fault. The jeep track emerges into cleared land at the boundary of the Volcanics and the Buchan Caves Limestone. Mapping of the contact has shown the latter to be unconformable on the former. The basal sequence is rather similar to that at Buchan: dolomites passing upwards into calcarenites 'with Splnella buchanensis and Chalcidophyllum recessum in abundance. Micro-grained lime stones (calcilutites) tend to come in higher in the succession, as at Buchan. A typical locality with these forms silicified,together with Syringopora flag_cida and sp. can be examined on the descent to Bindi Creek. This locality is about the middle of the formation.
191 172 LOCALITY 34 - Bonanza Gully, Bindi. This is near the top of the Buchan Caves Limestone and is stratigraphically higher than the highest beds of this formation at Buchan; it was extraordinarily rich when first collected. The fauna included an abundance of atrypoids including large, near-sphe rical forms, and species of Nadiastrqphia, Coelos_pira, Sghizophoria, Conocardium, Parapugnax, Cariniferella, Carinatin_a, Parachonetes, Prokopia, _Quadrithyrina and Calceola as more prominent forms. This horizon corresponds generally with that occurring at about the middle of the Pyramids Member at Buchan. LOCALIT Y 3 5. Outcrops of Taravale Formation at Bindi are poor owing to deep development of kunkar and alluviation of streams. Typical fossil collecting localities on hillsides consist of runs of boulders containing tabulate corals, stromatoporoids and Receptaculites. The be st section of these sediments is along Old Paddock Creek north of the area, but outcrops are not richly fossiliferous. Two or three typical exposures will be visited, the first being on the south side of Lime stone Creek opposite the junction of Yapp's Road and Bindi Road. LOCALIT Y 36. Another high Taravale Formation locality on the south branch of Lime stone Creek just downstream from Yapp's Road. LOCALITY 37. A 4 to 5 hour detour would enable examination of the base of the Buchan Group at Mt. W3~t 1'S0f1Where B1Ch3H Caves Limestone rests indiscrirninately over fault blocks of Snowy River Volcanics and Cowombat Group, the latter striking ilmost at right angles, and the former at a few degrees, to the Buchan Caves Limestone. Other features of interest include the Cowombat Group marbles, conglomerates and fine-grained detrital sediments along Old Hut Creek. Then proceed down the Tambo Valley crossing belts of granitic rocks, metamorphics and little-metamorphosed Ordovician sediments to Swift's Creek, and thence via the Baldhead and Morris Peak roads to Tabberabbera. LOCALITY 33 - _ _Loc._95, Tabberabbera}. Cherty Ordovician sediments exposed in a road cutting near two branches of Dead Bull Creek. Exposures in this vicinity can be taken as typical of the Ordovician sediments of the Tabbe rabbe ra area; graptolites he re are rare or poorly preserved. LOCALITY39 _- (Loc. 9 r,_ T_abber_a_`Q_bera). About 12 chains past the Wentworth crossing. Cherty sediments containing Climaco-.graptus (4 spp.), Cryptoggaptusgtricornis, Dicellograptus sextans, and species of Diplograptus, Glossograptus_ and Leptograptus, the ensemble indicating a Lower Gisbornian age. It is from this locality that supposed radiolarians said to be similar to Tamworth Group (Middle Devonian) forms were recorded. FIFTH DAY ;.oc_/3.l1t Y_4o. Wild Horse Formation - basal conglomerates and grits of the Wentworth Group as exposed on a new road across Swarnp Creek to Dargo. The Devonian sequence, less tightly folded, rests unconformably on the Ordovician succession, the strike of the main 'tailf of Devonian outcrop lying at an angle of about 20 to the predominant strike of the Ordovician sediments. LOCALITY 41. Lower sandstones of the Kilgower Member exposed in new cuttings on the Dargo road.
192 1-73 LOCALITY 42 - (Loc. 35, Tabberabbera). Richly fossiliferous silty claystones in the Kilgower Memb-er. Prominent species are Fenestella dargoensisp, Philhedra acutilirata, Muriferella punctata_, Nadiastrophia superba, Cymostrophia bellarugosa, Parachonetes baragwanatlli, ep1ialaria? longisepta, Adolphia glypta, Howellella t_extilis, Cypriclardinia crenistria. A Lower Emsian age is indicated for these and other rich faunas at about this horizon. LocAL1TY 43_. Outcrops of limestone within the Kilgower Member on the ridge crest east of Loc.42. There is a swarm of intermediate dykes in thisvicinity and on the slopes of Hundred Acre Ck., some of which have assimilated lime stone. LOCALITY 44. Lower Roaring Mag Member - silty claystone and sandy siltstones outcropping in Stack Gully. These beds at Loc. 37, Tabberabbe ra, contain large orange fleckings, which, in thin section, are seen to be broken crystals of felspar which have disrupted the bedding, bending it downwards - products of a shower of pyroclastic material evidencing contemporaneous volcanic activity. The sediments contain poorly preserved spirife rids and auloporid corals. LOCALITY 45.- Loc. 34, Tabberabbera). Claystones and siltstones higher in the Roaring Mag Member with poorly preserved bivalves. LOCALITY 46. Thin-bedded limestones associated with siltstones and claystones of the Roaring Mag Member about the saddle of Horseshoe Bend. These contain comparatively rare, poorly preserved brachiopods, probably identical with Sppinella buchanensis, so characteristic of the Buchan Caves Limestone and the Bell Point Lime stone, elsewhere in eastern Victoria. The flats and gentle slopes on the opposite side of the Mitchell River are occupied by the Angusvale Diorite, the largest intrusion of the Tabberabbera Dyke Swarm. It has metamorphosed Wentworth Group sediments, but in the south is overlain unconformably by late Devonian Avon River Group sediments. Its period of intrusion is thus fixed precisely in the inte rval from late in the Tabberabbe ran Deformation to prior to initiation of the nonmarine Upper Devonian cycle of sedimentation. Proceed back to the Wentworth River, then over Sandy's Creek towards Glenaladale. LOCALITY 47. Non-marine, pebbly, Upper Devonian sandstones, typical of the Avon River Group,outcropping about l mile south of Sandy's Ck. Deeply weathered rhyolites inte rbedded with these sediments outcrop poorly near the base of the sequence. LOCALITY 48. The Upper Devonian succession is exposed in road cuttings along Freestone Creek, north of Briagalong, where there are excellent exposures of the basal conglomerates of the Moroka Glen Formation, of the Wellington Rhyolites, and the Snowy Plain Formation (Neilson, 1964).l'ragmented fishpremains from sediments closely associated with the Wellington Rhyolites indicate a late Devonian age.
193 -_ M H 174 SELECTEQ RIj_; `_f_erences Beavis, F.C., The geology of the Kiewa area. Proc.Roy.Soc.Vic. 75 : Broadhurst, E., and Campbell, J.D., Geology petrology of the Mt. Leinster district. 45 : Crohn, P.W., The geology, petrology and physiography of the Omeo district, northeastern Victoria. l_13_id_. 62 : Fletcher, K., The Snowy River Volcanics west of Buchan, Victoria. lllicl. 76 : Gaskin, A.J`., The geology of Bindi. 55 : Moye, D.G., Sharp, K.R. and Stapleton, D.H., Geology of the Snowy Mountains region. Snowy Mountains Hydro-electric Authority. _ Neilson,.T.L., Geological map, Moroka, 1:63, 360. Geol.' Surv. 'Vic, Talent, J.A., The Devonian of the Mitchell and Wentworth Rivers. Geol.Surv.Vic. Mem. 24: Talent, J.A., 1965a. Geomorphic forms and processes in the highlands of eastern Victoria. Proc. Roy. Soc. Vic. 78: Talent, J.A., l965b. Stratigraphic and diastrophic evolution of central and eastern Victoria in Middle_Palaeozoic times. l i_d_. 79 : Teichert, C. and Talent, J.A., l_958. Geology of the Buchan area, east Gippsland. Geol.Surv. yi, Mem. 21: Whitelaw, H.S., Some limestone and marble deposits in east Gippsland. l_/ll13;g_gol. Jour Vic.,A 5 (3) ,--. :W-. ',.»f ' ' _..,/- ' ' ] 21+ J-f '7T7'f / r - - ga* *._t,.. _ 5 ; =f' ' -:f'» é-` _._ -;- 'U /.. 1. _,.3-iff' ' Qr ! ', N / / 1 1.IM1*I stoine.4uhf_ndel RIVLIP /»lfl7a (lf0. ; H; nmztt A.w.How4Ltt - Pfwg. Rep. Geol. Sufw. Vic., 1876.
194 175 CHA.PTER 18 PALAEOZOIC EVOLUTION OF EA.ST-CENTRAL VICTORIA by M. A. H. Marsden REGIONAL SE TTING. East-central Victoria is notable for Upper Devonian volcanic and granitic complexes occupying large cauldron structures, and for the occurrence in the eastern Upper Palaeozoic belt of Upper Devonian volcanics and thick Upper Devonian and Lower Carboniferous non-marine sediments. These rocks lie unconformably on bedrock ranging in age from Cambrian to epi- Middle Devonian(Fig. 1). The Cambrian rocks occur in two narrow, complex belts usually bounded by high-angle thrusts. The belts correspond with important tectonic axes, the meridional Heathcote Axis in the we stern part of the region and the Mt. Wellington Axis, which trends NNW, in the eastern part. Along the latter axis, Cambrian rocks outcrop in two sub-parallel belts, which are well exposed in the Howqua and Jamie son valleys and are consequently referred to as the upstream (easte rn) and downstream (we stern) belts respectively. The axes have long histories of tectonic movement, and the central Victorian region, between them,had a different geological development from that of neighbouring regions of Victoria. Rocks predominantly of Upper Ordovician age form the bedrock east of the Mt. Wellington Axis, having been stabilized by epi-ordovician folding. In east-central Victoria however, Ordovician rocks are only known along faulted anticlinorial axes within surrounding Silurian-Devonian sediments (Mt. Easton Axis, Mt. Useful - Phosphate Hill Axis). These occur parallel to and just west of the Mt. Wellington Axis (Fig. 1). The bedrock between the Heathcote and Mt. Wellington Axes consists predominantly of folded marine Silurian and Lower Devonian sediments deposited conformably on the underlying Ordovician. These were deposited in the central Victorian trough whose margins were delineated by contemporaneous upward movements of the axes, sufficient to expose Cambrian rocks along the Mt. Wellington Axis during the Lower Palaeozoic. The main folding of the central Victorian trough occurred during the Tabbe rabbe ran 'Orogeny' (epi-middle Devonian), and formed NNW-striking anticlinoria and synclinoria. Tectonic effects were more severe in the zone of the Mt.,Wellington Axis and in the adjacent Silurian-Devonian sediments than in the more stable region east of the axis. Intense deformation was not restricted to a linear axis but occurred over a wide NNW-trending zone of weakness. Superimposed structural_ parallelism is shown by the regional strike of fold axes and cleavage in the Silurian-Devonian rocks, the latter increasing in i1'lt I1SitYin the _eastern part of the central Victorian trough. The Woods Point Dyke Swarm also has a general NNW strike and was intruded into the Silurian-Devonian shortly after the Tabberabberan folding. In the eastern Upper Palaeozoic belt Upper Devonian and Lower Carbonife rous terrestrial sediments and Volcanics we re deposited in a trough elongated parallel to, and astride the Mt. Wellington Axis which is now only partially exposed. The present boundaries of the belt are often faults or monoclines, and its continuity is now broken by two oblique anticlinal structures, the northern of which is called the 'Howqua-Rose High'. The tectonicsetting gf this trgugh, and its fill, contrast with the Upper Devonian cauldron subsidences of central Victoria, in which acid Volcanics (with associated granitic intrusive s) predominate. Cauldron-like volcanic accumulation, with unusually large volumes of sediment, only occurs in the Upper Palaeozoic belt at its northern extremity (Tolmie Highlands). CAMBRIAN GREENSTONE BELTS OF THE MT. WELLINGTON AXIS. The downstream Cambrian belt terminates in the north at the Howqua River. The upstream belt outcrops in the region of the Howqua and Jamieson Rivers (Localities 27, 28, 29)
195 »~f~ ff* /Y* /~/` Af* k_ AA - f* ' -~ Aléuvlum an.v /v ' 'V Ower 21 ff* of* DOO le Recent; Granitic Rocks I Tertiary Igppgr Devonian ' 'V` ' M f4q - V Cgrboniferous t M '` < Late,_A _, Q Tertiary Cauldron ` $ '` 1-7<;? - Volcanics Complexes ~` % M nn an /V' AA -- 'iv n ' Silurian ` 0 ~ - fn An nn fv~ I -- / .. ~. sl,_,` _,_?A`Q9 }/// / _ aao`ng 1; Y (_ f & to r <1ov1c1an ' 7 ' '` r ` ' + + `-at /5H] GHL inds» _ 1 / / -'Route ~ / 'M.1 ' ' /' WEX' 0*--- lies 1 - -'Ml' '21 o o ' 0. ' / ' ' M. _g ` + N _ 9 o o I C? V ' ' ' Seymouri' + + » M -ildansfiefd /Q ' Xi'-` 3._ + + /'~ <, - `.: =»:' '~., f.` . L, _-x ','I 07- o Q I' +4 K ` + :B'inda;ee v. 1? Aiexandi-ag_. ~ gig-, Q..-ov/< G 7j g;f1a1l&' Lower Devonian»v,_A ~/I f '` M I I+ + 'I' + // Cambrian w QQ ` V,f - ' 0 0 _ ' . . 0 0 V (_) v ' NS*- A i Q` ~. f$ x 'v :_-S=;;' %3 `. ..`»v ~ ~`. Oy 0 o _ 9 ` mi ` .~. - .A. l,- * )>, 5* Q 0 O V E-4 / V <5 Y. ..1 f / ` -CA _ 0 Eastern_Up er V.>,C ) ' ' T. ' `-,5_) _ ' _ Palaeozoic elt, ` V 53 l ' x dm »' / / fa. l o > V V I lj. J L +Marys- I V V V,'v Q- y 'Y + ivilljl /f-, f .$ Q); v v v ` 77,- : H + I / _,.» A { 0 V V VQ V V H /I v v v rf,_»~`, ,'////_. s 0 * I O, ' _ .'5Q 5? 0 ` / W % QQ? . ' _,'f Woods o if, Qu ~ Point._/3, 0 9 V V V V 'Q' V l/_~,l-'r1 2_t1f=.Sfi11e J Q tw $éa~ ~ O 0 0 V V V V Vs f -:Zn // -. ' gcq.,q 0 O V V V V - I, _--*T ~- Warburton <P Q ~ ' v _,- /_ 1 dale, n 0 <9 o o Y. V V V V wav* /_ , ~ O O V V V Melbourne.// Q ' V ~, /, ~..1 ~»-,._ '`g _F M - -/ _,_ _ ;.~..}. awaihaiia Fig. l. Regional geology of east-central Victoria, showing route described (based on l : 1,000,000 Geological Map of Victoria). and has probable extensions south to the Dolodrook River where late Middle to early Upper Cambrian trilobites are known (Thomas and Singleton, 1956) and 1101 th t0 Ta120ng (Locality 41). An isolated outcrop area near Dookie may represent a further northward extension. These belts contain unknown thicknesses of spilitic basalts, pyroclastics and associated cherts. Low grade dynamic metamorphism and metasomatism is prevalent, comparable with similar rocks of known Cambrian age elsewhere in Victoria. Amygdaloidal, dense basalts are dominantpccassionally containing original augite and feldspar showing typical textures. Very fine, dense tuffs are common and are often platy and splinte ry Coarse-grained doleritic and dioritic rocks may be intrusive but the field evidence is usually obscure. The rocks weather to a bright red-brown clay which typically supports scrub-free open forest and,or grass. Extensive alteration producing greenstones ('diabases') usually includes albitisation (Ab ), an analysis by Teale (1919) of a greenstone from the 1-lowqua upstream belt showing 7. 0% Nag()-. Chlorite, hornblende and actinolite, epidote, lawsonite, carbonates and silica are common secondary minerals.
196 ; '.>.~...., Cv~..,-' ~ ~...:'..,-''~,.)' ~. ). _~ ' 5 '. '. ( - - ' - I.,1.,/. '.',' -/ I l~ Fig. 2. GEOLOGICAL MANSFIELD REGION MAP OF THE 7fo Representative d' 1pS tt... Horizont a l beds Antic! ' 1ne and syncline Grapt o l' 1t e l ocalities Locality number Road o - ;2.~., MT. COBBLER f -- --, . . ~6 ' ~ :-.---~ MERRIJ IG [26] ' ~l'i R :h~ -'- [3Oj- - -'- H H ',~~, J''.' -j'--'; It-'1i~'- ,~ - ' M, ~ oj I H I I ~ I '-I ~,f MT. STI RLING./ : I --' H GRANODIORITE / ~... H H H H ~.-..., ' '. MT. A.. SPECULATION t.;-:ej ~ I gn eous Rocks Ba r j arg Granite Acid volcanics - Rhyolite (Mt. Timbertop) Rhyodacite (c.f. Ho llands Basal Rhyol H e 'A RE GIONAL GUIDE TO VICTORIAN GEOLOGY' THE BLUFF Hornblende M Aplit e LOWER PALAEOZOIC granodiorite et c. ~ Ordovician Sandst one t 0 Lower Devonian greywackess, rntudstones e c. ' CAMB RIAN ~ Greenstones M.A. H. M. 1967
197 90 Fig. 3. GEOLOGICAL MAP OF THE TATONG AREA AND THE TOLMIE HIGHLANDS IGNEOUS COMPLEX ( AFTER BROWN, 1961 ). LEGEND AS FOR FIG. 2, IHTH THE ADDITION OF THE FOLLOWING : w ~ clj=j UPPER DEVONIAN Barjarg Granite and St r a thbogie Granite Gr anod i orite Po r phyrite Toombu11up Rhyodacite (and ~1 t. Sama r ia Volcanics) Rya ns Creek Rhyolite Holla nds Creek Rhyo dacite and Conglomerates e t c. o 2 N MILES
198 ln the Howqua River area, especially on the crushed western flank of the upstream belt, talcose rocks are common. Fine-grained talcose rocks were probably originally tuffs, but strong shearing has usually destroyed any original structure (Locality 27). Elsewhere (Locality 29) massive talc rock still shows relict coarse grained basaltic textures, iron staining and gritty fragments rendering most of it unsuitable for commercial use. Occurrences of serpentine (? chrysotile) have been exploited 'spasmodically on a small scale.. Replacement of greenstones by chalcedonic silica and quartz is prominent, at times along fractures some of which parallel the strike of the belt, but more often forming massive irregular patches up to 100 square yards in area. Typically such replacement produces bright red jasper, often with quartz veins, and less commonly green jasper, silicacarbonate rocks, and reef quartz. (Locality 2.9). A mineralised zone at Howqua Hills, with quartz, pyrite, pyrrhotite and other sulphides and gold was worked in the l88o's. Elsewhere, alluvial gold was derived from greenstones, as for example in Stockyard Creek, where talcose rocks are the source. Intense folding (Localities 27, 28) and shearing are prominent within the belts and the incompetency of many of the rocks has probably been important in localising the later tectonic movements of the Mt. Wellington Axis. Singleton (1965) regards the Mt. Wellington and other meridional axes (Fig. 1) as fundamentally controlling sedimentation and tectonic development in central Victoria during the Palaeozoic, being axes of intermittent upwarping. Cambrian Sedimentary Rocks. No sediments are known interbedded with the greenstones, although in two areas greenstones are overlain by cherts. On the Howqua River, the upstream greenstone belt is succeeded on its eastern flank by an apparently cornfortable lenticular belt about half a mile wide of? Cambrian cherts and splintery blue shales - the Howqua Cherts (Thomas and Singleton, 1956). Teal (1919) recorded Protospongia sp. and possible radiolaria in the cherts and Harris and Thomas (1938) recorded Lower Ordovician graptolites (Lag) near the top. Massive cherts and those with irregular thick bedding (up to % inch or so) may be primary, but many show regular, fine stratification and are silicified tuffs or shales. Che rts also occur in the Tatong area. The Tatong Chert formation which apparently conformably overlies the greenstones along their plunging northern boundary, consists of about 100 ft. of cherts and che rty shales containing inarticulate brachiopods. The abundance of fine mica in some cherts indicates they formed by silification of shales (Brown, 1961); some other cherts in the area are silicified tuffs. These sediments are overlain by clastic sediments with further che rts, and the whole sequence possibly ranges from Cambrian into the Lower Ordovician. ORDOVICIAN SEQUENCES OF THE AXIAL BELTS. Ordovician rocks only outcrop in narrow belts along the Mt. Wellington, the Mt.' Useful - Phosphate Hill, and the Mt. Easton Axes. Singleton (1965) envisaged upwarping in the vicinity of the axes during sedimentation, causing slow deposition of thin sequences, possibly containing significant unconformities. Phosphate rock is locally associated with these axial sequences, which contrast with the normal thicker sequences of greywackes and shales flanking the axes. In consequence, much less tectonic movement would produce the present juxtaposition of sediments of considerable age difference than if the normal thick sequences had been deposited in the axial regions. A. Mt. Wellington Axis. Eastern segment - Howqua River. The upstream Cambrian greenstone - chert sequence is gradually succeeded eastwards by greywackes and phyllitic slates alternating with sandstones and thin black slate bands dipping generally east. Graptolites of Lower Ordovician (Lancefieldian, Bendigonian) and Middle Ordovician (Upper Darriwilian) ages have been recorded (Harris and Thomas, 1938). East of 8-Mile Ck. green mudstones and sandstones of possible Silurian age succeed the more typical Grdovician. To the NNW in the Delatite River and King River valleys, contact metamorphosed massive quartzite and siliceous hornfels suggest that similar rocks continue along strike (Localities 33, 36). A uniform sequence of strongly folded and cleaved slates and minor sandstones occurs in the region of the upper King and Rose Rivers further east. Contact metamorphism of these on the King River has produced hornfels and 177
199 178 chiastolite slates. Upper Crdovician graptolites occur on the Rose River (Harris and Thomas, 1941) and this area is probably part of the eastern Victoria region. The structural relationships of these rocks to the Silurian belt and to the Cambro-Ordovician of the Mt. Wellington Axis are not known. _ edi1 _nents b_etwee_n u;p_stream arid _downstream gregnsjzone bel1;s_-_i-l9_w_g ua_river_. The upstream greenstone' belt is faulted and sheared along its western margin. Between it and the downstream belt are severely crushed black slates with subordinate sandstone, which dip predominantly we stwards. ln one area graptolites range from high inthe Middle Ordovician to IQW in the Upper Ordovician and are remarkably preserved (Harris and Thomas, 1938). In comparing these with the Lower Ordovician east-dipping rocks east of the upstream greenstone belt, Teale (1919) commented that an enormous downthrow on the western side would be required to bury a thickness of Lower Ordovician comparable to that known on the eastern side. The two sequences, however, show lithological differences and may not be comparable in thickness. lt may be more reasonable to interpret these areas as condensed axial sequences. The presence of Upper Ordovician phosphatic breccia between the belts supports this vi ew. We stern segment - Howqua River. West of the downstream greenstone belt, we st-dipping shales of fairly high Upper Qrdovician age occur. These are lithologically similar to the presumed Upper Ordovician of the Rose and King Rivers previously discussed. Harris and Thomas (1940) have suggested that this area may also contain a belt of Silurian sediments. Tatong Area. Overlying the Tatong Chert are shales, micaceous and feldspathic greywackes, and cherts, with poorly preserved inarticulate brachiopods (Locality 44). The sequence probably ranges into the Lower Ordovician since Middle Ordovician (Darriwilian) graptolites are known just north of Tatong, and Upper Grdovician occurs extensively further east on the Ryan's Creek - Middle Creek divide and in the Rose River area (Brown,l96l). B. Mt. Useful - Phosphate Hill Axis. Ordovician outcrops occur in the Upper Goulburn valley north of Mt. Useful (Upper Ordovician), east of Knockwood (Middle Ordovician) and at Phosphate Hill, we st of Mansfield(Thomas, 1939). At Phosphate Hill (Locality 25) a small inlier of extremely contorted thinly bedded shales and granular dark grey to green phosphate rock contains Lower Ordovician (La 2_3) graptolites. Aluminous phosphate (wavellite, turquoise, massive earthy phosphate) averages approxmately 10% P205 but shows great variation. Adjacent yellow-grey shales and black cherts show ages up to Upper Ordovician. The sequence is not complete and is complicated by strong deformation. C. _ Mt. Egton A3cis_. The Mt. Easton Axis flanks the Walhalla Synclinorium on its we stern side and linear faulted outcrops of Upper Ordovician occur along it from Mt. Easton to Mt. Matlock south-we st of Wood's Point, at Enoch's Point on the Big River (including Middle Ordovician), at an area on the Delatite River some 8 miles north of Eildon, and at Bonnie Doon (Thomas, 1947). s1lur1an-devon1an Rocks or THE CEN'I'R_ALq v;gtor1a '1 12.q _J<:.;-1. Sedimentation continued in this trough without interruption from the Ordovician to the late Lower Devonian or perhaps early Middle Devonian (Talent, 1965). Mudstones (often greenish) and sandstones are typical, and shallow water conglomerates and lenticular lime stones occur,more particularly higher in the sequence. Regional facies variation is apparent, and graptolite faunas become generally subordinate to neritic shelly faunas, but much of the sequence is very poorly fos silife rous. Two recent developments of note in Victorian Devonian stratigraphy are, firstly, the recognition that much of the sequence previously called Silurian probably extends well up into the Lower Devonian (Jaeger, 1966), and se'condly,recent radiogenic dates of approximately 360 m. y. for the Cerberean Upper Devonian lavas (McDougall et.al. 1966) indicate that this sequence, may be older than previously thought. They suggest that the age of the Upper Devonian- Carboniferous boundary should be increased correspondingly.
200 BARJARG ' A FAULT 2000, 2000 BROKEN RIVER ~ I + I 1: BLUE RANGE FAULT ~ HOLLANDS TIIIX' T1-: I(1' J ARY BA SALT, 0 STOCKYARD CREEJ.( FAULT 1 RYAN S CREEK MIDDLE 2000 FEET TOO~I I1ULLUI' BASI:'; TOOMBUL LUP NO RTH SYNCLINE ( afte r Brown, ) J MANSFIELD SOUTH 4000 FAULT BLUE '~r _man S FI ELD BASIN EVA-' S KINC ~ 4 RANCE CREEK RIVER - >IT. EASTERN BOUNDARY FAULT RO SJ K TYPO ::::1..-- =_ :;--.;::::~:-~ r:;:~,... :~.. I:r::-::-,I:~.~:~:~.-. ~:~.:.-.:.:~.~ ~:~ -~.;1.::~~~i. :.: ~~ :~~' --:~r~: _ ~.~ :.:: -:..,...-, ~~ I :: ~;~~::;-;:;::;; :;;i: ;::;;.---:- :;; ; :; ::::;O::;;;:::;;'..:c~,;;.'Eu~~u~u~u~uU'-~~ - ~- - -~1~~---<~'l'uj'u.cruFu::.:a::2us:::iBu5'I:~tJ:j1 ;:~: 4000 ~ FEET 4000 FEET :::::... ' 4000 MANS Fl ED ' FAULT I' I ' MERRIJIG I BUTTERCUP CREEK I I01,.;QUA-ROSE ' III GH' ~T.~~~~'(:;_--~~~~~~~~. ~.~ ~ ~ ~.~E:L:A:TI~T~E~RI~V:E:R ~.:_--~~-~~--~~~~--~~~~~~~_; '--' :... ~-. -'-' -.-. ~ HT. EVERE TT (KULLOCK ' S LOOKOtrr ) M ~ HOWQUA-ROS E 'IIl CH' ~ RESIDUAL OF IIASAL RHY OLITE-'.N. A.H. M.19 fl o FEET HI L ES NO VERTICAL EXAGGERATION ~ -.~.. ~. +- HOWQUA ROSE 'ICH' ' >IT. TlMIlERTOr LOI~ER CARBON I FEROUS CONGLOMERATE 4 ~rr. JlULI.LH R HRT IARY lasalt [)!:[.ATITI: RI TR l H H H H H H H H H H - - 'IT.~ ~ RLl:-;r. s-- H H H H H H H H H H H H H H H TIiORNE RAN GE H ~ H~~H~~-~ ~~~-~ ~~ --~ ~5ei;~:t H H H H H H H H M.A. H.M : o FE ET 'A REGIONAL GUIDE TO VICTORIAN GEOLOGY ' Fig. 4 Geological s ections of the Man s f ield r'q 1 o n.1nd the Tolmic HI qh l...lnd s Igneous Complex The lines of s ection and l egend are s h','n on Flc; :'>. 2 and
201 U 1Ls-:; _~ ~' FT- ~ _law Fl / 6 Hum FT... PI..XT-( Kfl T0l. Tli mans ' _és I ' _ ll.._ 5 _/ / f 1/ A/ _~ '_ SPY -Nzw FULL Sl} P[_y _»;'r_ _--- - w..' _' _'_' , ow nm '<x- S `. _ ,l l 4, f ei! / //Z/4//Q/Z/' / /// / 1/ / / gm* -41, _s' //////J Q. l '. - -f--yy--' r riff' /» - // E-.~; is f/ ~_ -_ ~_.- : <.1Nr:1is.x._ >s on _s _gf _: _; _~ 4 ` ff / _MAINLf_'lj!lICl» u unto /-././ /_ /_.f / FT -_ ~.. YDb_T0!;I!;S! _* V, _y{ s ND_ fp3_r.> _AN[?_ UDS; `0N '. E NI.' l' >> » ;_i _p >ls>: :U W' <:m; _x SHALE--1-L-->4--EILDON s:, ~»:. mcnsq _' <----- '_»' l; 9'-, ; 1x_: ~ ' SECTION THROUGH SUGARLOAF. T.. ;; U / f / _Af _,; ' g 'll / '/1, 4/ //Q/ xtu rl'.l sl' ~l_',r;' _ ll -.45 y,_ mm H' 1/ <'ol' uu»<~; < ' f < -if ' 'T i n (_, / / / )`»~ ' // /I - I, /// ' //,I-. / _', L/f if 4. f mf 4 / /e' MN' H-» < v EILDON Bans ~ 6 ' A rr.` 5 ff/ L1 L/ _ l 'mf' IJ 4 E L*''`; SECTION ALONG SPILLWAY CUT. Fig. 5. Geological sections through Sugarloaf abutment and along spillway cut, Eildon (after Thomas, 1947). The top section through Mt. Sugarloaf was prepared before its exposure in the present quarry. The following summary of the development of the trough is essentially a modification after Talent (1965) (Table 1). 1. Deposition o_f graptolitic terrigenous sediments with no apparent break,occurred from Upper Ordovician to Llandove rian and Wenlockian time. In the we stern part of the trough this was followed by widespread deposition of the graptolitic Dargile Formation and its equivalents in the Lower Ludlow. In the eastern section Llandove rian strata are known from limited areas, but strata of Wenlockian and Ludlovian ages have not been proved. On the eastern side of the Walhalla Syncli_norium, strongly cleaved unfossiliferous greenish mudstones and sandstones (Mt. Useful Beds) are thought to be Silurian (Localities 20, 21, 22). Z. _Qeposition of the Mclvor Formation occurred in Late Ludlovian to Lower C-edinnian time, on a sea floor shelving from the Heathcote Axis eastwards into deeper water. Coarser sandstones occur in the west and grade into finer graptolitic sediments in the east with corresponding progressive faunal changes. The Eildon Beds (1, 000+ ft. thick) may represent poorly fossiliferous deeper waterequivalents of the Mclvor Formation. These occur on the southwe st-dipping limb _of the major Eildon Synclinorium, which shows conside rable minor folding and variable plunge. At the base, mudstones (Fig. 5), followed by thicker sandstones are overlain by massive calcareous sandstones containing small patches of fairly pure lime stone (Locality 18). The massive Eildon Sandstone forms a prominent marker, and mudstones and fine sandstones occur at the top of the Eildon Beds. Dendroid graptolites occur below the calcareous sandstones, which contain crinoid stems, corals (Heliolites, Favosites) and stromatoporoids in limestone inclusions (Thomas,1947). Monograptus aequabilis, indicating a Lower Gedinnian age, occurs near Matlock in more argillaceous equivalents of the Eildon Beds, containing the oldest dateable Victorian Baragwanathia (Jaeger,1966) (Table Z).
202 180 _T _BL_E 2.1 pc<or_1;e_laltiioln of _earlygdevp_nian of' central Victoria (after Jaeger, 1966). Walhalla Group Emsian Tanj 11 Nowakia sp Slegenlan Formation. Zone of _, M hercynicus.., -Q -_ 1-» -_ 4-. -pq Wilsons Creek _PL thomasi I B hi Shale cf. gf. praehercynicus' -éiégy-éhe'~ +--Q,. 6; or I Gedinnian Eildon Beds M aeguabilis (Upper part) (formerly _PL vomerinus..! 3. Deposition of the Mt. Ida Formation with thick sandstones and conglomerates occurred near the western shore line in Upper Gedmnian time. East of the Seymour-Healesville line contemporaneous deposition of sediments of the deeper water plant-graptolite facies occurred over a large area inter tonguing with sandstones on the west. At Eildon this facies 1S represented by the Wilsons Creek Shale which contains Monograptus thomasi previously M uncinatus) w1th Baragwanathia (Jaeger, 1966; Berry, 1965) (. Locality 18 ).... Jaeger indicates that _l_/l_ thomasi is very close to M. _praehercynicus and characterises the highest graptolite zone known from Australia. Shelly fossils including nautiloids are occasionally found. _Mg thomasi and Baragwanathia also occur near Matlock, well above the equivalent aeguabilis horizons of the Eildon Beds. The Wilsons Creek Shale is a prominent unit, ft. thick, mainly of black shales, used by Thomas (1947) as a key mapping horizon. Ove rlying the black shales are olive and black shales and thin sandstones similar to typical graptolite occurrences at Yea and Alexandra. 4. Depositiog of the Tanjil Formation (and equivalents) occurred in Siegenian times. This becomes more sandy towards the north, and at Eildon the equivalent is known as the Norton Gully Sandstone, which 'CQ the north where it is Lmfossiliferous. The characteristic Tanjilian Pganenka-Styluioliria shelly fauna Can be approximately related to the horizon of _li/i_; hercynicus by tentaculitids (Nowakia sp.) occurring well above the M. thomasi zone. Q;,}_De;pq_sitioi1_ occurred in Upper Siegenian to Lower Emsian times of the Walhalla Group with impersistent conglomerates and limestones at the base, the younger beds being poorly fossiliferous. At Eildon the basal equivalents are two or more impersistent and thin conglomerate horizons. Sandstones contain shelly fossils and plants, the succeeding thick shales being unfossiliferous. At Loyola, a lens of dense limestone occurs on the eastern flank of the Walhalla Synclinorium (Locality 24). The fauna includes corals, stromatoporoids, brachiopods, gasteropods and nautiloids (Hill,l939). The deposit is small but has been used for agricultural lime and crushed lime stone. At Lilydale, shelf conditions permitted deposition of the Lilydale Limestone which has a rich coral-stromatoporoid-mollusc fauna, and is younger than the Loyola Limestone. The Walhalla Group and the older Baragwanathia bearing beds in the eastern sector may have been partly derived from a source area to the east (Singleton,1965). Greenstone pebbles in conglomerates suggest that the Mt. Wellington Axis was exposed near the eastern shoreline.
203 Upper Devonian Givetian Heathcote -RedcasUe Puckapunval- SeVJ11.our East -Broadford Lilydale Yea -Alexandra -Buxton EUdon-Jamieson Matlock Woods Point Walhalla Upper Devonian u.sian Siegeniln RUDDOCK SILTSTONE Mauispitiler ~')UUC, K horizon Loyola Limestones NORTON GULLY SANDSTONES 4= TANJIL FORMATION SIR JOHN FRANKLIN BED~ENTENNIAL BEDS JOHNSON HIL~ SANDSTONES not dillerenl;afed Limestone on Deep 0, Walhall. Gedinniln Ludlovian ~3EP~le;ur~o~di~cty~u~m~-JS~lr~op~h~o~ne;ill;;a lbe3;dd~s -=-=~-=:=--::;~~'WILSON CK SHALE 2 Noloconchidium Beds 'IT IDA BEDS EQUIVALENTS 1 M oloogia Beds 3 Upper Rhynchonellid Beds MC.IVOR 2 I amcl!;6'4och Beds FORMATION 1 l ower Rhynchonel/id Beds.fdiWt~siM;;~~~u s Beds 2 Graplolile Beds (M. ousano; Zone) - DARGILE FORMATION 1 Lower Dargile Mudstones MC.IVOR AND EILDON EQUIVALENTS CHRISTMAS HILLS FORMATION t? WILSON CK. SHALE - MATLOCK FM.,'1'~l:T) 'NolanoP1.ia SWde ipper plant graptolite... horizon?--? t -r'~ ~,_T _r _r ~,~<~O~.k~siC~r~it Ejldon Sandstone Dendroid horizon xu MucophylluM Conchidium' Beds )IIIICJUUtx Monog,aptu! ~.b i/js horizon EILDON BEDS _ MATLOCK FM. UN:r::A~~' NlJljll' 7 position 01 lower pl.nf p,'pfolile horizon ~,I lolillll.'oul Wenlocklln Ind ludlovlln Ittatl not known In thll I>.lt_ Wenlockian.Llandoverian Upper -----'jy~~~~+~tj Lower ---- 'll/ifriuscjinc;- COSTERFIELD FORMATION '0.1 Wenlockian.lr.l. nol known In thl. 1> ENOCH'S POINT BEDS 'AULT CONTACTII _ ST. CLAIR FORMATION IN PA., Wenlockian Llandoverian Ordovician Ordovician TABLE 1. Generalised east-west section through central ~ toria showing relationships of the Silurian and Devonian ( from Talent, 1965).
204 Regressiorl of the sea from central Victoria is indicated in the Eildon District by the Cathedral Beds which are resistant red and yellow sandstones and shales. They show cross bedding, ripple marks and mud cracks and contain only poorly preserved plant remains. A SE plunging syncline forms the easterly dip slopes and the steep we stfacing escarpment of the range, the foot of which is masked by extensive talus and alluvial fan deposits on the eastern side of the Acheron Valley. Near their contact with the overlying Upper Devonian volcanics, the Cathedral Beds show dips of about , indicating a strong unconformity. Conformably underlying the Cathedral Beds and 3, 500 ft. stratigraphically below, are Lower Emsian fossils in a sequence typical of the Walhalla Group (Dale, unpublished). Probable equivalents of the Cathedral Beds occur on the south-east margin of the Cerberean Cauldron (Koala Creek Beds). 7. The_maj_or period o_f foldi1_rg_, the Tabberabberan 'Orogeny', occurred during the interval of post-eifelian to some time in the Upper Devonian. LATE MIDDLE TQ EARLY UPPER D1=:vQNLA_1 I IGNECUS ACTIVITL Following the Tabberabberan folding, intrusion occurred of the Woods Point Dyke Swarm and also of three sm_a11, closely inter-related plutons, mainly of hornblende granodiorite, east of Mansfield (Mirimbah Granodiorite, Mt. Stirling Granodiorite and a small pluton on the Howqua River - Localities 32, 33, 34). These all appear to be related in age and petrology. No dykes are known to cross-cut the Upper Devonian or younger rocks either in the Marysville Igneous Complex or in the Eastern Upper Palaeozoic Belt, and the Upper Devonian sequences can be demonstrated to unconformably overlie the granodiorite plutons. The Mirimbah Granodiorite is faulted along its north-eastern and north-western boundaries, and is not intrusive into the Lower Carboniferous (Anon, 1961). Recent K/Ar age determinations by the Australian National University (McDougall, personal communication) on the Mt. Stirling Granodiorite give ages ranging from 363 to 372 m.y., and one on a sample from the Mirimbah Grandiorite gave 369 m.y. A sample from the Morning Star Dyke at Woods Point gave an age of 380 m.y. These are not inconsistent with the field evidence that these rocks are older than the main acid lavas, but nevertheless sugge st a Late Devonian age. The rate of erosion necessary to expose these intrusions before the main Upper Devonian volcanic phase is not excessive under the prevailing conditions of regional instability. The significance of the Rb/Sr age of 369 ll m.y. for the presumed Upper Devonian Barjarg Granite and Ryan s -1- Creek Rhyolite is not clear (McDougall Q gl., 1966). Generally the Dyke Swarm intruded along fractures with the regional NNW strike of the newly-folded Silurian-Devonian sediments, over an area of some 2, 500 square miles (Fig. 6). plutons, in contrast, were intruded near to and east of the Mt. Wellington Axis in a different tectonic regime, and into rocks with different physical characteristics favouring intrusion by stoping. Lamprophyres and diorite porphyrites of intermediate composition predominate in the Dyke Swarm which includes a wide range of rock types from ultra-basic peridotite and perknite, basic gabbro porphyrite and mela-diorite to acid quartz porphyry and granophyre,the latter representing a re stmagma (Hills, 1952). The Dyke -Swarm also has the following features:- (a) variability of texture and mine ral proportions in individual dykes linking ultra-basic to (b) (c) (d) acid types, crystallization following the normal reaction series, predominance of lamprophyric types indicating crystallization in the presence of abundant volatiles, post-crystallization tectonic movements with subsequent introduction of aurife rous quartz veins, Hills (1952) szigge sting that the gold-bearing solutions may have been derived from the intruded sediments, and not from the dyke magma, Ultra-basic and basic rock types are restricted, as far as is known to the eastern margin, this and other features suggesting progressive development from the eastern margin. Many features of the plutons are analogous to those of the Dyke Swarm. Lateral variation in composition is pronounced and may occur even at hand specimen scale as patches or ill-defined 'veining'. Fe rromagne sian minerals formed from primary crystallization and also from normal The
205 H 182 reaction, forming rims or partial or complete pseudomorphs. Olivine, hypersthene, c11no pyroxene (augite, diopside), hornblende and biotite show the se features in the various rock types. Basic to intermediate rocks occur rrnst prominently in the northern part of the Mirimbah Granodiorite and in the small Howqua River pluton, but do not represent a very large proportion of the intrusions by volume. The most basic rock known from the Howqua River pluton contains olivine, clino pyroxene and bytownite (An85). Nearby is rock with hypersthene, diopsidic augite and bytown ite (An-70_80), the ferro-magne sian minerals showing incipient reaction. Patches of this rock contain hornblende, biotite and quartz. This grades to rocks having an approximate mode of labradorite (An55) 51%, diopsidic augite 25%, hornblende (and other amphibole) 21% Depending on the extent of reaction, the ferromagne sian mineral may be more or less entirely amphibole. Hypersthene is occasionally present. Quartz may be present in small amounts but is always interstitial and potash feldspar is relatively rare. These rocks and the quartz diorites are generally finer grained than the granodiorite, and some of the more basic have doleritic textures. The hornblende granodiorite is gradational with the quartz diorite, having increased grain size and an enrichment in potash feldspar relative to the basic rocks. This feldspar forms as jackets on plagioclase, as perthite, as interstitial crystals and in cracks and veinlets Porphyritic texture is common and the rock grades locally into a chilled porphyritic border phase m _l 1-L _,pq- 17 F 7 ' D rf Q' * : Q + +,t 4 ' f 6 r 2 v + 4* Q w * _y ' is 1' 1- T `**' W ~ *_ 4- _ 'U *5 1' 4- c?/'f1» *f *pr * 3 (077 ' l ii -' :I s*->< ' QQ 14.' 5:17. X Q;-Q S s.-_,me < 1 1 'A`* U* _ A i I ` i$9` /f >f~»' `~ ~ -. + Z'~....~.~ 4 w = Q5 512`h* PUINY ` A ~FAA DVI( SWIHM 6 -, M To i _+ Q ' - 4 +~++ Q G 1 U -. ff M _/I /'/' 'n,if 1,. _, f N M- * + * ',_ f_: ` `._ ` ' l,.`_ /af.;' f/ / /.-- '»-_ J / O '/ /4 ///_ ~~` 'J miss ,./7 'Tj!,f L.. g k' '., -;r,# W f<~ l*`ig.6. Distribution of hypersthene-dacite suite of lavas and some related granitic rocks in central Victoria. Localities referred to in the text as follows: 1. Dandenong Ranges volcanics. 2. Lysteriield granodiorite. 3. Mt. Macedon hypersthene dacite. 4. Pyalong granodiorite (part of 5, Cobaw granodiorite). 6. Harcourt granodiorite. 7. Maldon granodiorite. 8. Mt. Disappointment. 9. Tynong granite. 10. Warburton granodiorite. 11. Baw Baw granodiorite. 12. Adwmn Cauldron. 13. Cerberean Cauldron. 14. Black Range granodiorite. 15. Strathliogie granite. 16. Violet Town Volcanics. 17. Mt. Kooyoora granite. ( Hills, 1959 )
206 183 Xenoliths in the granodiorite are virtually all basic igneous rocks and similar to the diorite, quartz diorite etc. previously described. Feldspar porphyroblasts are common and some xenoliths have an outer zone enriched in potash. Extensive aplites grading occasionally into microgranite are the final products of crystallization. These occur as dykes and veins in the granodiorite, and as segregations grading into it, as well as forming a large homogeneous body of approximately four square miles intruding the Mirimbah Crranodiorite (Locality 32). Pegmatites and vein quartz are rare and the only evidence of volatiles is extremely local marginal sericitization of the granodiorite. The overall evidence points to the magma having been relatively dry, in contrast to the volatile-rich magma of the Dyke Swarm, which may reflect the regional differences between the two environments of intrusion. In addition to the lack of reef quartz, another notable point of difference is the absence of gold associated with the plutons. If their magma is related to that of the Dyke Swarm, this absence supports the idea that the gotd associated with the Dyke Swarm was derived from the adjacent sediments. The magma of both the Dyke Swarm and the plutons was acid to intermediate in overall composition. The inhomogeneity of the plutons has its counterpart in the Dyke Swarm, which was presumably fed from a similar inhomogeneous magma in depth. Hills (1952) suggests that differentiation, chilling and differential streaming in the dykes and in the magma chamber could account for the variations observed, but, since this was the initial phase of the post-tabberabberan igneous activity, it is possible that completely homogeneous magmas had not as yet developed in this region, while hybridization may have played a part. The basic rocks of the plutons do not appear to be crystal accumulates and may represent rem» nants of an originally greater volume of basic magma. The lateral variation from the basic types is gradational, but the more homogeneous granodiorite shows differences from other types in texture, grain size and in potash feldspar content. The exclusively-igneous xenoliths presumably represent more basic magma which crystallised early, and there is no evidence of in situ assimilation of country rock. The extensive aplitic rocks bear some resemblance to the groundmass of the more chilled porphyritic granodiorites and appear to be closely related. Hills (1959) suggests that a relationship possibly existed between the magmas producing the Dyke Swarm and the younger rocks of the Cerberean Cauldron. He also suggests the possibility of extensive lateral movements of magma in the crust during this time, which implies the possibility of hybridization Basalts are known from the younger Upper Devonian sequences in similar small proportions, interbedded in the Cerberean Cauldron, and in the eastern Upper Palaeozoic belt. These may also represent material separate from_ the main magma, rather than differentiates from it. UPPER DEVONIAN TO LOWER_CARBONIFEROUS SEQUENCES. Extensive terrestrial post-orogenic sequences, unconformable with all older rocks, accumulated under contrasting conditions, viz. A. Upper Devonian Cauldron volcanic and granitic complexes of central Victoria e. g. Marysville Igneous Complex (Acheron and Cerberean Cauldrons) (Fig. 7) and the Strathbogie Complex. B. Eastern Upper Palaeozoic belt, with interbedded Upper Devonian volcanics and Upper Devonian to Lower Carboniferous non-marinesediments comprising ul. Tolmie Highlands Igneous Complex at the north end, with thick cauldron-like volcanics and sediments, and 2. elsewhere, thinner interbedded volcanics occur towards the base of a predominantly sedimentary sequence.
207 184 TABLE 3. _Ggneral Sgcggssion Q f Qpper Qevggian Cauldron Seguences _ 'EERBEREAN CAULDRON ACHERON CAULDRON strathboc1e (1) COMPLEX (1) (2) Thickness (2) (3) in feet 2A.Hybrid rhyodacite 4.Hypersthene dacite UPPER 2.Quartz-biotite- + hypersthene Hypersthene» biotite 2.Quartz-biotite -hypersthene CERBEREAN rhyodacite rhyodacite dacite + ACID Transition through Quartz- VOLCANICS toscanite. Sharp biotite FLOWS break at N end. dacite. Variants Quartz dacite + l.nevadite 700 l.nevadite l.rhyolite TOSCANITE Fragmental Acid GROUP Volcanics (ignimbrite). 500 'Fragmental Toscanites' TAGGERTY Basic Volcanics GROUP (Basalt, andesite, BASIC tuffs) Andesite xenoliths in later flows -- SERIES Shales, sandstones, &c. with Upper Devonian 250 fish LOWER SNOBS 3.Biotite~rhyodacite Acxn cam: nd fuffs smuns voncmxcs 2 R' ' » l.rhyo1ite (Soda rhyolite) Basal Conglomerate 20 + TOTAL approx Modified from:- (1) Thomas (1947) (2) Hills (1959) (3) White (1954) A. Cauldrons of central Victoria. Several polygonal or elliptical cauldrons occur in central Victoria (Fig. 6), sometimes having an early phase of relatively thin, restricted Volcanics and sediments. The major phase of collapse produced very thick, extensive flows characterised by porphyritic texture indicating intratelluric crystallisation. The parent magma was probably acid to intermediate and the characteristic sequence from acid to more basic (rhyolite to hypersthene dacite) resulted from pre-extrusion vertical differentiation. Consanguineous with these are plutons of granite, adamellite and granodiorite probably intruded into subterranean chambers formed by major stoping collapse along elliptical or polygonal fractures (Hills, 1959) (Fig. 6). Upward stoping by parent granitic magma after extrusion of the lavas has often brought it above the original surface level, to intrude and metamorphose the lavas. Large scale
208 W f i l 185 Eildon >.ALEXANDRA EILDON Reservoi r 1 0 ` [13] 0 a I Allgvigm etc. ` omitted ' _*_ I GOULBURN R. ` LOWER DEVONIAN _*_ ` SILURIAN Cathedral Beds ;_ Stippled + + : lv/ ` I A + ` I/' [13] I 1 ` / O A _*D Q / 3 Q* _'_ II //.M't Q. Q /. MILES A + / /._ /<%n wg, <= Q Torbr ec k 7 [19] / /// I _+_;*;AC 4 }_ >, ;f_-12' A ' /CERI E&{N / /<F/ / +_,++_l_++ _{ I Q4 lt// / / E / / + ~ R af // `// _* *_ RANGE _*_ 4, A// / / '_ I / / `i' + + 4' `+', X `/ / / / /-~ + _*_ + _* + I / X /CAULDRON / f / / / 1 '+RING ' / / / c > / / / / / -..oy1<e W +I (_ / / W A -+- -}- LJ 0 >1.w.'sv11.LE [8 9] / /. C, ' ' '+` ~ I ' c; J c 3 3' [2] C 3 C UPPER.DEVONIAN Q I S ur., ', J /L;? Granodiorite J CBlaclP Lg C,' I A Intrusive Rocks, A IYOOHR ; Adamellite am 1],_A Q / // (63 Q~',»~ I D `/ / l_ F />:,; /y / _ Granodiorite Porphyrite M d k D f/'-''c1 Q / W I/ HEAL S%L% ; QAULDEOL/! Hornblende Porphyrite I W % / Q Qufégglizlfiiéfiiéiéte-Hypersthene ; /` / // / Q? Extrusive Rocks / wg/ Hypersthene Dacite / /Z % I / / QVQY ` ~k ~`/ E _ /_ Q Ji? I Quartz-Biotite Rhyodacite 'ey Q `~=/ Quartz Dante 4 I/ Nevadite _L_ L0C3lif>' Fragmental Acid Volcanics + + +, / Road Taggerty Group T Sno_bs: Creek Volcani s Fig. 7. Geology of the 1 1I'}'S i lle Igneous Complex ( after Hills, 1959 ).
209 186 fissure filling also has occurred forming dykes such as the Cerberean Ring Dyke and the Black Range Granodiorite which is a large, partially filled arcuate fracture split into two minor fractures at its southern end (Hills, 1959). The similarities of the stratigraphy of the cauldron- sequences and their detailed petrology, are most striking (Tab1e3). l. Acheron Cauldron. Early sediments and Volcanics are generally absent and the main sequence is analogous to the Cerberean Volcanics. The quartz dacite and quartz biotite dacite are regarded as variants (Hills, 1959) although the quartz dacite may be somewhat older (Edwards, 1931) (Localities 1, 2). The hype rsthene dacite is similar to that of the Dandenong Ranges and has its maximum thickness in the south, wedging out to the north due to tilting during collapse. The bounding fractures are both arcuate and linear and are filled by granodiorite and granodiorite porphyrite (Hills, 1959). Granodiorite intrusions at the complex boundary between this and the Cerbe ran Cauldron show a wide range of hybrid rocks including altered sediments (Locality 8). Quartz-biotite-hypersthene dacite occurs along the northern margin and is locally intrusive into rhyolite (nevadite) (Edwards, 1931) (Locality 3). Z. Cerberean Cauldron. The cauldron, miles in diameter, is underlain by a central block o_f Silurian-Devonian sediments, on the eroded surface of which accumulated discontinuous and variable sequences of sediments, and central-vent Volcanics, during early, slow downwarping,which was pre-nevadite (Table 3). The be st developed sequence is at Snobs Creek (Locality 17) (Fig. 8), but similar sequences are seen elsewhere (Locality 13). The Basal Conglomerate is sporadic and probably diachronous. Pebbles of sandstone and quartzite are up to 1 ft. in diameter. The Snobs Creek Volcanics include porphyritic grey rhyolite with roc_k and charcoal fragments in a cryptocrystalline matrix, which grades up to rhyodacite. lnterbedded tuffs have abundant biotite in parallel orientation. At the base of the Taggerty Group, lacustrine yellow, red and greenish tuffaceous shales and sandstones occur which, in the Blue Hills east of Taggerty, contain a key horizon yielding Upper Devonian fish (Bothriolepis gippslandiensis, Dipterus mic rosoma and Phyllolepis sp. ) (Hills, 1931). The se are overlain by a marker unit of dense basalts, andesites ('me1aphyres') and tuffs. Restriction of the Snobs Creek Volcanics and of thick basalts to the we stern side of the Snobs Creek Fault suggests contemporaneous faulting within the cauldron parallel to the grain of the bedrock (Fig. 8). The inward dips (25O- 340), measured at the present eroded scarp, of the older units are greater than those of the younger flows, but the se p'robably flatten out towards the centre. The widespread Fragmental Acid Volcanics (ignimbri tes) fore shadow the main phase of collapse. The rocks have a grey, black 'chert-like' matrix with shattered phenocrysts and abundant small xenoliths. ` The main extrusion of some ft _ of Volcanics followed immediately, the first nit being a thick extensive porphyritic rhyolite with microgranular matrix (nevadite), containing minor cordierite and almandine. The rock is blue-grey, weathering to buff. and forms the main escarpment. At the base it may be fragmental and has little biotite, grading up to biotite nevadite at Snobs Creek. To the south, continuing increase in plagioclase and biotite gives a transition through toscanite to quartz-biotite-hypersthene rhyodacite (Localities 7, ll). The latter overlies the biotite nevadite sharply in the Eildon district, and is the final and major flow (and most basic, in the absence of hypersthene dacite), with a ve ry extensive central outcrop area. It is medium grained with phenocrysts of quartz, abundant biotite, plagioclase, hypersthene, rare orthoclase and garnet in a microgranular matrix. Coarser and more acid schlieren with gradational boundaries are characteristic, and in its upper part the rock is strongly hybrid, containing blocks of quartz porphyry and garnetife rous granodiorite porphyrite which match the ring dyke types, their origin probably being related to the mechanism of extrusion.
210 '.,.. ;>, -.,- 'V '... ~...--.:::-c'... -:.~o~ ...,.... 'to ~ , , ~~/'l I' Al... ~. r.to Granodiorite Porphyrite. r:juartz Biotite Hypersthene Rhyodacite. Nevadite. Fragmental Acid Volcanics. [R-Rhyolitel. rv-vl Basic Volcanics LY-.J etc ~ ~ f?cl ~,.-/, Rhyodacite and Biotite Tuffs Rhyolite. - -.:::' Road..,...~..,.. Fault Basal Conglomerate I... ;-1--/ / / / -/ --I /....../... / --I /... --I --I o F I... / /... /... / / /... / /... /.../_... I... / / /... / / I 1... / 1 1 'l --/... / /... 1_ / -/... /... / / I-I --/... / /... /... /... /--/... /... / /--1 --I SCALE Miles 1 t rl Walhalla ~ Group. r:::'::'1 Norton.,;... Gully Sandstone. N [Mag.],...,..,.. I Alluvium. F F J Fig. 8. Geological map and cross section of the north end of the Cerberean Cauldron and Ring Dyke (after Thomas, 1947).
211 N 188 / A Av T Eurii / / / C9_1lTACT-Z,0NE _gi / ' / / / / /. + I +I' / [2] Locality 1 Road A ` A _ I' FIRM] / // _, +, / / / ' + / / / O 1 + 6_*''»/ / MIIES O +'I' 'I' ;+- T, A Iva / Q31 1 I 'I' I /I: / G ` * + 1 / /I,V ' Q +* ` / 'I' 'I' *I* / / / ' /» Q/ +' I f / / '+ +`I if. A E ~= If ]`r+(_+;`_++ /» 5/ / / } gf K / / A; A 4' Qgg -/.,?, af1< f/ ` +1-*+;+I-ff; 1-ri d if + + / A / A J' -In : ` - m,l UA ON Q J + 5 / 'I' 'I ++-Ql;++_Ij`_ ` ` v ` `,L[I}5]_Ir E I If S U Benalla' QI ` ` 2 nu,h N' '_ to + ` 'I' A li /al' Q an /'A ` ` ~ '-/' + s + + ` ~ -1 _ - f ' + + lllllllllllllll llll, f I Cl I f f ' N,f -. tiav.f ' RECENT Qiiuf, f Alluvium éi CY1o1et Qown I LATE TERTIARY,<» Q /I / i' Q] B Q><' /I A Llmburgite,_ ab / A / A V..» A V I UPPER DEVONIAN %<, ' it / ( / / / A/ X» V.j;.OJ'c.t_ 'lemf/el <=ee.i.c» 177 / /f / / A A / ` - - Euroa I / A '~ A / Quartz - Biotite - I, AP- / A / Hypersthene`Rhyodacite ' Q / f ` / / /, Granodiorite -I# (BX [46]/ [45] I g g. I / PO`['phy`]'. ]_t 1* + r -0' I l _ I +» - I 1 ' Rhyolite 'I _I I;~ _I_ I I _ L _L_-I' I- -I* _*_ Barjarg I_ Stragthjbgogige Grani te -I- ' - *I* -I- -I- -I- - -_ -I-Gap I --_- L - Leucogranite -'I- I r I I I» I I- --I-I T 1' ' I +I. Aplite If _ P;:;:;r;`;eC AI- 'I' _'I' 'I' 'I' I I_ P _ SILURIAN *, / ap' IIIIII I I I I H Miles 4 4 Fig. 9. Geology of the Strathbogie Igneous Complex (after White, 1953). A. Contact zone between Violet Town Volcanics and Strathbogie Granite. B. Map of Complex. C. N-S Section through Complex.
212 189 The Ring Dyke is variable in texture and ranges from the predominant granodiorite porphyrite to quartz porphyry - the former is correlated with the uppermost rhyodacite and the latter with the nevadite (Hills, 1959). It varies in width, rarely being more than % mile, dips outward generally at and is regarded as the main feeder channel, although minor 'splinter fractures occur. Vertical movement of ft. has been estimated stratigraphically from the displacement of the basal conglomerates of the Walhalla Group at Snobs Creek, but may be more in view of the total thickness of fill of ft. 3. Strathbogie Complex. The lavas (Violet Town Volcanics) occupy a cauldron to the immediate north of the Strathbogie Granite, the boundary being an annular fracture along which the steeply upwarped lavas show evidence of metamorphism. Major stoping along polygonal fractures accounts for the rectangular boundaries on the southern side of the granite where normal hornfels aureoles occur. Thin rhyolite is followed by about 1500 ft. of quartz-biotite-hypersthene rhyodacite with schlieren similar to the Toombullup Rhyodacite (Tolmie Complex) and the Cerberean hybrid. Intrusive features in the rhyodacite and a granodiorite porphyrite intrusion have been interpreted (Hills, 1959) as a marginal dyke-like intrusive zone related to the feeding mechanism (Fig.9). Aplites gradational with granite are concentrated along the rhyodacite boundary and are cross-cutting. Tourmaline nodules and pegmatitic veins occur in the aplites (Locality 46). Fine grained porphyritic leuco-granites are also gradational with these rocks (Locality 45). B. Eastern Upper Palaeozoic Belt. Post-orogenic downwarping along the eastern margin of the central Victorian fold belt produced an intermontane trough at least Z5-30 miles wide, in which thick sediments with volcanics accumulated. The present boundaries, often major faults or monoclines, are probably related to the original depositional boundaries. Rapidly-wedging extensions of the thick sequences of the belt must have over-lapped the pre sent boundaries to some extent but have since been eroded. The belt is cut by the northeast-trending Howqua-Rose structural 'High' which separates the Tolmie Highlands Igneous Complex and the downwarped Mansfield Basin from the southerly extension of the belt. Differences in Upper Devonian sequences on either side of the 'High' indicate that it approximates to the position of a controlling structure which existed early in the history of the belt. Thick cauldron-like volcanics in the Tolmie Highlands Complex contrast with minor volcanics and thick sediments to the south, which are largely the product of rapid contemporaneous erosion of volcanics and granodiorite from the upwarping 'High' (Bindaree area). Relatively thin volcanic and sedimentary sequences in the vicinity of the upwarp itself are transitional (Mt. Timbertop, Mt.Cobbler areas). Thick Lower Carboniferous Red Beds without volcanics overlap the older formations. l. Tolmie Highlands Igneous Complex. The sequence below is for the northern part. Little is known of the southern part (Upper King Valley) where thick rhyodacite with agglomerates overlying a thin flow-banded basal rhyolite are faulted against the northern margin of the Howqua-Rose 'High'.
213 190 TABLE 4. Tolmie Hi hlands I neous Com lex Se uence after Brown Lower Carboniferous Red Beds, etc. Unconfo rmity Barjarg Granite Toombullup Rhyodacite ? ft. Main- Complex Ryans Creek Rhyolite ? ft. Basal Conglomerates ft. Unconfo rmity Hollands Creek Rhyodacite ft. and Conglomerates, etc. Unconformity to older rocks In the Hollands Creek 'cauldron', intermittent and small collapse movements permitted deposition of considerably more sediment than in other cauldrons, at least four horizons of thick lenticular sediments being inte rbedded with relatively thin ignimbritic rhyodacites which increase in importance upwards. Subsequent diastrophic folding, rather than 'drag' during collapse, has frequently caused dips of 450 or greater, increasing to vertical and even overturned. Mas sive and poorly sorted conglomerates with boulders up to 9 in. are dominant Pebbles of quartzite and greywacke are abundant, with reef quartz, chert and jasper in a sandy matrix. Sandstones and pebbly sandstones are common and red siltstones and sandstones also occur (Locality 43). Antiarchan fish plates (?Upper Devonian) occur low in the sequence. Brown (1962) regards the rhyodacites as ignimbrites. Conspicuous irregular dark lenticles represent lava fragments with planar orientation due to flattening on compaction (Locality 42). They contain fewer and larger euhedral phenocrysts, which were protected from shattering during extrusion, whereas other phenocrysts are angular and show wide size variation. Associated agglomerate plugs contain fragments of rhyodacite and bedrock ranging from microscopic size to 3-4 ft., in a tuffaceous matrix (Locality 41). The lavas of the main Complex lic-2) unconformably on the Hollands Creek unit. In the Toombullup Basin inward dips of 40 may signify collapse (Brown, 1961), but evidence for their thickness is scanty. The volcanics have low dips in the Toombullup North Syncline, which may only be a continuation of the post-lower Carbonife rous Mt. Typo Syncline. Granodiorite porphyrite outcrops (Locality 38) probably represent feeders but no definite fracture pattern has been demonstrated. The Ryans Creek Rhyolite shows graditional features without major discontinuities and is probably a single extrusion. The Toombullup Rhyodacite contains schlieren of granodiorite porphyrite. The final phase was the intrusion of the Barjarg Granite into volcanics c.f. Toombullup Rhyodacite near Mt.Samaria. 2. Sediments and Volcanics of the Eastern Upper Palaeozoic Belt. The sequence is terrestrial, mainly fluviatile, and almost unfossiliferous. Upper Devonian fish remains occur in the South Blue Range near Mansfield (Phyllolepis sp. and Bothriolepis sp.), overlain by rhyodacite (Locality 23). Hills (1935) placed the Upper Devonian-Lower Carboniferous boundary at the top of the rhyodacite, which is disconformably overlain by thick Red Beds
214 ~. SOUTH BLUE RANGE BINDAREE THE BLUFF AREA MT. TIMBERTOP AREA MT. COBBLER AREA Lower Carboniferous -Red Beds - usually 5000' ' thick, with feet of basal conglomerates etc. TOLMIE HIGHLANDS IGNEOUS COMPLEX BASE I_x - OF +RED BEDS ~ _I Unconformity to Lower Palaeozoic 1000' SO~' 0' APPROX. SCALE 'Red beds' Fish bed 8000' abore base. - - Basal conglomerate 1-' ' s-l /lnconformity._ i i'fi~~i' Unconformity to Lower Palaeozoic and granodiorite 'Red beds' -.. Biotite. rhyodacite,.-. etc. with interbedded sediments -.':'.- Mudstones and fine arkoses, etc. Arkosic conglomerates and arkoses, etc. Basal rhyolite Unconformity to Cambrian, Lower Palaeozoic and granodiorite 'Red beds' Rhyodacite Basal conglomerates, etc. _ 'Red beds' Basal conglomerate I:. ~ ~~' -,.--I:':',...-g 7(?) Conformable_~O 11-_ -- Unconformity to Lower Palaeozoic and granodiorite Fig. 10. Diagrammatic sequences of key areas of the northern part of the eastern Upper Palaeozoic Belt. Legend as for Fig. 2. M.A.H.M Mudstones, arkoses, etc. Thin basal conglomerate 6000' Rhyodacite I I Basal rhyolite 2,000' j I.....,/:: ~'~;~~~:I. ~.': :'.. ~~~;'.~h ~ Unconformity to Cambrian, and Lower Palaeozoic 'Red beds' Basal conglomerate Unconformity', Toombullup Rhyodacite Ryan Creek Rhyolite Angular unconformity Holland Creek Rhyodacites and Conglomerates, etc. Fish remains -0...
215 192 (Fig. 10) containing Lower Carboniferous fish (Woodward, 1906) and associated Leptophloeum mansfieldense about 3000 ft. above their base in the Mansfield Basin (Locality 36). Lo cal angular unconformities occur between the Red Beds and the underlying Upper Devonian in tectonically active areas, although normally the junction is conformable or dis conformable. The Red Beds have a prominent basal conglomerate and fairly consistent thickness and lithologies. Volcanics are unknown within them, but in places occur immediately below, often followed by intervening erosion. For these reasons and in the absence of fossils, the base of the Red Beds is taken here as the regional base of the Lower Carboniferous, although this may well be a diachronous feature. Some correlations are suggested by lithologies and structures, but persistent formations may also be diachronous. The sequences in several important areas are set out in Fig. 10. (a) South Blue`Range - Jamieson Syncline (Localities Zl, 22, 23). The basal Upper Devonian conglomerates occur within a red or brown mudstone unit in bands up to Z5 ft. thick, totalling perhaps 100 ft. They are poorly sorted and are characterised by profuse= angular pebbles of reef quartz, and greenish mudstones and sandstones (cf. Silurian bedrock) in a red mud matrix. Pebbles of quartzite are common and jasper, chert and greenstones also occur, but volcanic materials are unknown. Sandstones and conglomerates separate these from the underlying rhyodacite. The large thickness of the sequence is probably. related to its proximity to the basin edge, where tectonic effects would be most felt. An angular unconformity with the overlying Red Beds exists for example near the southwest corner of the Mansfield Basin, the structures being complicated by later folding of the Red Beds. (b) Bindaree - The Bluff area (Localities 34, 35). This sequence is notable for the massive boulders beds near the base, up to 30 ft. thick, with in. boulders being cornmo ranging up to 4 ft. These grade into conglomerates, pebbly arkoses and arkoses, all poorly sorted. The pebbles may be almost exclusively rhyolite, but quartzite, rhyodacite, reef quartz, hornfels, chert and hornblende granodiorite occur also. The glassy flowbanded Basal Rhyolite in the Mt. Cobbler area is probably among the oldest igneous rocks in this area and its erosion has supplied the pebbles. Little rounded and relatively fresh feldspar and quartz grains often give the rocks a pseudo-igneous texture. The unit is very variable and includes sandstones, red and brown mudstones and siltstones with lenses and patches of arkose. Interbedded volcanics are rare and thin, and many of the rocks thought to be pyroclastics (Harris and Thomas, 1938) are sediments( (c) Mt. Timberto area Localities 27 Z8. This is a thinner sequence deposited on or near the 'High'_ and the basal unit is not only thin but contains locally derived stable materials (chert, jasper, greenstone, mudstone, sandstone pebbles) with rhyolite pebbles and feldspathic material. The overlying rhyodacite is very similar to that of the South Blue Range and volcanics in the King River valley. The red rhyolite ignimbrite is unique in the region and shows oriented lenticles in a fragmental glassy matrix. This area is not continuous with, and shows many_ differences from the Jamieson Syncline area. (d) Lower Qaprboggerous Red Beds. The Basal Conglomerate has pebbles of quartzite, sandstone, grit, chert, jasper and occasional volcanics up to 9 in. but more commonly Z-3 in. The matrix is usually sandy. It outcrops around the edge of the down= warped Mansfield Basin except in the northwest corner where sandstones and grits occur at the base. In the Mt.Cobbler - The Bluff belt the basal beds may be grits, sandstones or even siltstones. Red sandstones and siltstones, the latter increasing in relative abundance upwards, dominate the overlying sequence which is at least 6000 ft. thick. The sequence shows much less lateral variation in lithology than the more local Upper Devonian sequences. 11
216 Regional folding is absent although, along the margins, beds may be vertical or overturned (Localities Zl, ZZ) due to so-called 'drag'. These are high-angle structures reflecting bedrock structure, and are better regarded as fault-folds or monoclines in which localised compression may have played a part. The Mansfield Basin, the corresponding anticlinal Howqua-Rose 'High', and the Mt. Typo Syncline are broad, strongly asymmetric structures and are essentially low-dip tilt blocks with respect to the Red Beds, with deformed edges. Unusual marginal folds in the SW corner of the Mansfield Basin have steep inward NNW plunges which die away very rapidly. The se developed in the acute-angled corner in response to accentuated compression during downwarping. Structures in the bedrock shales and in the nearby Upper Devonian belt reflect the 'folding' of the unconformity during this deformation. The north and north-east margin of the Mansfield Basin is an unfaulted unconformity overlying the Tolmie Highlands Complex in part, and the beds have a regional 5-10 dip ssw. -v--p -»- Fault or Monocline -Oi-l -ft 'Anticlinal' Axis 1)_:_-`:`_ 'Synclinal' Axis Low Regional Dip & -T-':''-l /( m Moderate Dip Fig. ll: Structural Features 7 13 ' _C ' *'., Steep Dip D D. of the northern part of the N l Ki ' X; 0 Overturned Eastern, Upper Palaeozoic belt. :. ;` X G X E ; Mt Z Timberto Mt Cobbler -» ' $,;; '-._' :. xt..'.t. 5. '_T'_-'* l. Mt Howitt Cambrian of Mt. Wellington Axis. H ' 'I' } _ /o», - B.. The Bluff M Mansfield 2. Howqua - Rose 'High'. +)~ 1' + ` :B 'X T' - Tg I Tatong' + ff 'T'-- '' =z '.+ + _ '. _:_ 3. Mansfield Basin. N -qnn.lp -P+ Q 4. Mt. Typo Syncline. * 5./_~.-_. + lk/44..~ :_ 5. Tolmie Highlands lgneous Complex. 1 _,_. L _.... L 5. _Z,.,..., A. Hollands Creek 'Cauldron'. B. ;.. (9.f.'Lf...>'.. '>»:7 Toombullup Basin. ll SQ: ' C. Toombullup North Syncline. 3- f'..-f'. s. rg* '--/ 1651 D. Stockyard Creek Fault.... '»».yi { :.?=._ I».»..`,.,...'...'.h. 1 4 ' 9 ':'.. 6. Jamieson Syncline. 8 0,11 ` Nm '1- ' 410 '.1 'Ei o L i f' 0.. a 0 _ H 7,.. 7. Barjarg Fault. . '. ' if- =-.`. '., g' Mansfield Fault.... O 4 lg. _ ` }?: I:-lf; -._ -;.', H in-n-i _ xi»1 fi* :, :z-ia..'.'. 9. (North) Blue Range Fault _ Q Miles Q ~f` M ~ l E. - `, ozs.'f oa 10. Pinnacle Fault., O _? `~. ' 3 A B.... L Carboniterou ll. Eastern Boundary Fault. 'Red Beds 2_ _ _ 12. Plunging marginal folds. Upper Devonian Vg:-_,;_`.}. _ - _ ' + + Granite zfzglg `: _ h ' Bindaree Monocline.. ='_.-5 Acid Volcanics Yig =1 ' ' E5 Sediments }3, 3 $ ' - _ & Cambrian ` f;zt ` '. Q Lower Palaeozoic (and alluvium M,A _H M 1 6 _ POST-LOWER CARBONIFEROUS ROCKS Early Tertiary Basalts. Older Volcanics cap a number of highland areas in the Tolmie Highlands, Mt. Buller area, and east of The Bluff, often with sub-basaltic freshwater sediments. Tinguaite dykes,.which are fairly common in the same region, and a phonolite plug at Gallows Hill A. near Tolmie, are possibly older (Locality 37). Late Tertiary-Quaternary Basalts. The se occur north of Melbourne in association with well preserved vents. occupy buried valleys and cover much of the coastal plain The flows 193
217 194 1=3_H _` IOGRA_PH Y. The areas of Lower Palaeozoic sediments are well dissected and generally of lower elevation than the more resistant igneous massifs. The highland areas generally show considerable flat remnants of erosion surfaces of various ages, uplifted in the late Cainozoic and undergoing dissection. Streams show evidence of periodic rejuvenation and may have broad alluviated valleys, the Goulburn and its tributaries commonly having high level gravels perched ft. above present level (Localities 15, 31). The edge of the extensive northern Victorian alluvial plain, flanking the Highlands, is seen near Benalla. Differential erosion and structural control of landforms and stream patterns are very marked throughout, especially in the Upper Palaeozoic belt where excellent dip-slope and escarpment features are seen. The west-flowing section of the Goulburn River between Eildon and Jamieson has some anomalous features and it has been postulated that the Upper Goulburn originally continued north through the Barjarg Gap to Benalla. Tilting, followed by headward erosion by westflowing streams capturing the upper Goulburn headwaters, left the present Broken River draining through the Barjarg Gap as a beheaded stream (Fenner, 1914). ITINERARY FIRSTDAY IN TRANSIT - _Melbourne to Heale sville (37 m. ) Undulating Siluro-Devonian with cappings of Tertiary sands and gravels. Newer Basalt flow filling broad Yarra Valley, the present stream in lateral channel. At 7 m. scarp of Dandenong Ranges' Cauldron ahead (television transmitters). Older Basalt unconformably on Lower Devonian mudstones, and lenticular Lilydale Lime stone - Quarry at Cave Hill (ZO. 5 m. ). At m. road cuts lowest flow (Toscanite) of Dandenongs Cauldron. Christmas Hills to NW (Brushy Ck. scarp continuation) and Kinglake Plateau behind. Yarra Valley at Yeringfamous wine growing district (pre-phylloxera) (Z7'm.). At 29 m. Black Range Ring Dyke mas sif in distance on left. Watts River valley ahead, with Healesville-Warburton mas sif (Ache ron Cauldron) to right. LOCALITY 1 - Maroondah Dam (37 m_._). Melbourne water supply. We ste rn edge of Acheron Cauldron. Quartz dacite variant with prominent flat jointing. Proceed via Fernshaw (42 m. ), and climb Black Spur - Mountain Ash (_l )_. regnans) replanted after 1939 bushfires. Deep weathering. ;._Q_cg.,L1TY 2 : On Black spur (44_mL_)_. Quartz-biotite dacite variant. LOC_f 1l;_._1'l;Y _3 7 DOI_l]_D_9fI2 &dd1 (46 m. ). View across incised Acheron Valley. Distant plateau of Marysville Complex, Mt.Torbreck, Cathedral Range withthe Cathedral at NW end. At B1adin's Quarry, quartzbiotite-hypersthene rhyodacite intrusive into nevadite, on northern edge of Acheron Cauldron. Proceed to foot of scarp of Volcanics (48 m.). Siluro-Devonian to Marysville (58 m.) at foot of nevaditc scarp.
218 195 IN TRA_NS1'If_ 7 JMa _ysvi1_1e tp u_mbe_1_jland River (10 m. 2. LocAL1'1 Y 4. Base of Upper Devonian sequence very weathered. Basalt cores in red clay (1 rn. ). LOCALITY 5. Fragmental Acid Volcanics (1. 5 m. LQCALITYg 6. Nevadite scarp of Rob1ey's Spur and cauldron edge.. View down Taggerty River valley, Black Range to west, Strathbogie Granite in distance with Goulburn River valley in front. Conical hill near Buxton - Ring Dyke. LOCALITY 7. Nevadite - toscanite - biotite rhyodacite transition up the sequence ( m.). LCCALITY 8 - Culvert (3_._8 m._). Granodiorite and zone of xenoliths etc. (to 5.1 m.). LOJCALII! 9 -_Lake Mountain turnoff (6 m. 2. Zone between granodiorite dykes to Bellel Creek (6.5 m.) LOCALITY 10 - (The Big Culvert (9.1 m. 2. Garnetiferous biotite rhyodacite. LOCALITY ll - Cumberland River (10 m. Q. Sample acre of _1 _. regnans - highest known living tree in Australia ft. Rhyodacite - toscanite transition to nevadite at Falls. l.qcali'i_; _ li JBu;xt_9n Return to Marysville. Road. Adamellite from Ring Dyke. View of south end of Cathedral Range. Proceed via Buxton along Cathedral Range escarpment with talus slopes. Ring Dyke 'pods'. LOCALITgY 13 - Blue Hills Road, E of Taggerty. View of Cerberean Cauldron sequence. Unconformity, basal conglomerates, sediments, Fragmental Acid Volcanics, nevadite, biotite rhyodacite. Shearing probably due to collapse movements. LOCALITY 14 - Rubi_con,River bridgetsouth of '1_;`h`orntong. Ring Dyke - quartz porphyry phase. Flood plain of Goulburn River.
219 196 SEC OND DAY LCCALITY 15 - Eildon Road Ring Dyke occurrences. High level river gravels. Erosion surface of Puzzle Range to N. Enterprise Range to E behind dam. LOCALITY 16 - Snobs Creek Road. Ring Dyke - granodiorite porphyrite, chilled contact, xenoliths, outward dip. LOCALITY 17 - Snobs Creek Road. Section through Upper Devonian sequence. Basal conglomerate, Basal Rhyolite, biotite tuffs, etc. Basic Volcanics. Fragmental Acid Volcanics, base of nevadite, nevadite (in quarry), quartz-biotite-hypersthene rhyodacite with schlieren. Knickpoint at Snobs Creek Falls with broad, flatter valley upstream. LOCALITY 18 - Eildon Dam. Sugarloaf Abutment. Quarry and Boat Harbour Road - Eildon Beds and Wilsons Creek Shale sequence. Spillway Cut. Mudstones, etc. of lower part of Eildon Beds sequence. Head-on junction of Delatite and Goulburn River, fault? along edge of Enterprise Range. Second dam raised F. S. L. by 112 ft. IN TRANSIT - Eildon to Jamieson. Reference - Jamieson Map Sheet 1:63, 360, Geological Survey of Victoria. Skirt edge of cauldron around Mt. Torbreck, crossing Ring Dyke, etc. Dissected Lower Devonian in major synclinorium, less dissected area after Warburton turn-off. LOCALITY 19 - Rocky Ridge. Ring Dyke. Knick point of White Creek. Proceed via Big River, where Mt.Easton Axis is crossed. Traverse Walhalla Synclinoriurn - cleavage prominent.,views of edges of Upper Palaeozoic belt, Mansfield Basin, elevated area of Howqua-Rose 'High' (Mt. Buller), Strathbogie Ranges, etc. LOCALITY 20 - Between Jamieson and Howgua Rivers. Sheared olive green Silurian mudstones beyond eastern margin of Walhalla Sync linorium. LOCALITY Z1 - South_of Ma_rtin's Crip. Mansfield Fault at W margin of Upper Palaeozoic belt - shearing in Silurian, and in overturned Upper Devonian red basal conglomerates and mudstones. Martin's Gap - view of South Blue Range - fault line scarp on E side of Mansfield Fault, sequence dipping E into Mansfield Basin. Tolmie Highlands, Strathbogies in distance to N. High country to E of Howqua-Rose 'High'.
220 197 LOCALITY ZZ - Section across South Blue Range. Upper Devonian - Lower Carboniferous sequence and Mansfield Fault with deformation in Silurian (Fig. 10). LOCALITY Z3 - Monkey Gully. Rhyodacite ignimbrite. LOCALITY Z4 - Loyola. Syncline in Upper Devonian. Lower Devonian lime stone. LOCALITY 25 - Phosphate Hill. Grdovician sequence. IN TRANSIT - Mansfield to Bindaree (42 m. Q THIRD DAY with detour to Howgua River. Cross Mansfield Basin to eastern edge. Lower Carboniferous Red Beds - flat at Mt. Battery (1 m. ), regional dip in Springfield Hills (8 m. ). View of flat-topped volcanics, etc. at Mt.Timbertop, residual on upthrown Howqua-Rose 'High'. LOCALITY Merrijig. Lower Carboniferous sediments. DETOUR TO HOWQUA RIVER. Dip increasing. LOCALITY 27 - Timbertop Creek - Wild Dog Creek Divide. Upper Devonian lavas and Lower Carboniferous of Mt.Timbertop area. Steep west dip on downthrown side of Timber top Fault, against folded Cambrian tuffs (?), sheared tuffs, etc. LOCALIIY _ 2 - '[;im_b_e rtop Qap. Basal Upper Devonian sediments faulted against Cambrian. I1QCA_],IT_Yp ;9 _ Howqua River Cambrian greenstones, jasper, talc rocks. Cherts. Lower Ordovician sediments. Howqua Hills - gold town relics. Return to Merrijig and resume Mansfield - Bindaree traverse. LOCALITY 30. View of Timbertop Fault and Pinnacle Fault across Delatite River. ahead (14 m. ). Hornfels ridge
221 198 Proceed east to edge of Mansfield Basin where Lower Carboniferous dips at 800W (l4. 6 m. ). Cross Timbertop Fault, obscured by talus, at 15 m. Enter small gorge on Delatite River in Ordovician hornfels (l5. 3 m.). 'Amphitheatre' in hornblende granodiorite at 16 m. 'Rim' of hornfels, rhyodacite, Lower Carbonife rous and aplite. LOCALITY 31. Mirimbah Granodiorite, aplite, high level river gravels. View Mt. Buller (l6. 5 m. ). Proceed to Sawmill Settlement through gorge in resistant aplite (17 m.). dissected scarp of Pinnacle Fault in granodiorite (18 m. ). LOCALITY 32. Stoped E contact of Mirimbah Granodiorite (22 m. ). Cross the Proceed through Alpine Ash ('Woolybutt') forest - E.delegatensis. Stoped W contact of Mt.Stirling Granodiorite (24 m. ). Weathered tinguaite dyke (27 m. ). DETOUR AT 30 m. TO LOCALITY 33. Stoped S contact of Mt.Stir1ing Granodiorite with hornfels screen. at N contact of Howqua River pluton. View - The Bluff escarpment. Basic diorite, etc. LOCALITY 34 - Bindaree Section_Q6 :_ l2_m Q. Sheared grano- Traverse through Upper Devonian sediments (basalt, rhyodacite). diorite etc. infaulted. Bindaree 'Monocline'. LOCALITY 35 - 'Traverse to E end of The Bluff. Upper Devonian sequence with biotite rhyodacite at top. siltstones. Views of Eastern Highlands. Lower Carboniferous basal Return to Mt.Stirling Ring Road, and continue in anti-clockwise direction, returning to Mirimbah. Rhyodacite, granodiorite, etc., aplite. Structure of Upper King River, Mt. Cobbler area. FOURTH DAY IN TRANSIT_ - Mansfield to Benalla via Tolmie _and Tatong. LOCALITY; 36 - Barwite. Lower Carboniferous Red Bed sequence. Proceed up dip-slope to Tolmie Highlands. of Mansfield Basin. LOCALITY 37 - Gallowsgl-lill. Fish beds near North Blue Range. Fault with Barjarg Granite in NW corner Phonolite plug. Proceed via Tolrnie along Tatong Road. Older Volcanic residual - small quarry (l6. 5 m.). LOCALITY 38 - Madhouse Road (20 m.l. Garnetiferous granodiorite porphyry. 3 policemen at nearby Stringybark Creek. Ned Kelly country - scene of murder of
222 LOCALITY 39 - Descend to Hollands Creek Q - 25 rn. Q. Ryans Creek Rhyolite, Toombullup Rhyodacite, etc. LOCALITY 40 - Hollands Creek Q28 m. Q. Cambrian greenstones. LOCALITY 41 - Hollands Creek Valley. Upper Devonian vent agglomerates at 30 rn. and near Dodds Bridge. LOCALITY 42 - Ijlollands Creek Valley Q34.5 rn. Q. Hollands Creek Rhyodacite. LOCALITY 43 - Tatong Q37 rn. Lower Palaeozoic cherts, etc. Ryans Creek Rhyolite. Upper Devonian Hollands Creek Conglomerates, etc. Proceed to Benalla across broad alluvial flats, and thence to Violet Town. IN TRANSIT - Violet Town - Strathbogie Ranges - Euroa Q26 rn. Q. l._oc_i_ }LI'I;_Y_ 44_ - A_t foot of scarp of lavas Ql.l rn. Q. Quartz - biotite -hypersthene rhyodac ite. LOCALITY 45 - 'North of Mmsugarloaf Ql3.5 m. 2. Porphyritic leuco-granite. Proceed past Mt.Sugarloaf (14 rn.) along contact zone. LOCALITY 46. Aplite. Proceed to Euroa. Tourmaline nodules, pegrnatic contact zone with rhyodacite (17 rn. IN TRANSIT - Euroa_t_o I_/E_lb2urni_(IQ/Iileages from Melbourne). Proceed along west edge of Strathbogie Range. At 58 m. view up Goulburn River gorge in Strathbogie Granite. Siluro-Devonian bedrock, - poor soils. Newer Basalt at Kilmore. Mt.Disappointment granodiorite and Kinglake plateau to E. Aureole of Pyalong Granite to W (37 m.). Pretty Sally (29 rn.) - platey jointing in Newer Basalt. Descent from Siluro-Devonian to lower surface of Newer Basalt with wooded ridges of protruding bedrock. Scoria cones, etc. in source area of flows of Melbourne district. Views of Upper Devonian massifs to E, and Macedon Cauldron to W. Sub-Newer Basalt clay etc. at Campbellfie ld.
223 Z 00 BIB LIOGRAPHY ANON., History and Environment - Geology. Victorian Year Book 75: BERRY, W. B.N., Description and Age Significance of Type Monograptids from Eildon, Victoria. Proc.Roy.Soc.Vic. 78: BROWN, M.C., The Geology of the Tatong-Tolmie Area. Unp'ubl.Thesis Univ.Me1b. BROWN, M.C., Some Ignimbrites of Upper Devonian Age from Victoria, Australia. Bu11.Vo1cano1ogy 24: EDWARDS, A. B., The Geology and Petrology of the Black Spur Area (Heale sville). PrOCoR.OYoSOCoViCo 49'76o FENNER, C., Physiography of the Mansfield District. Proc.Roy.Soc.Vic. 26: HARRIS, W.J. and THCMAS, D.E., Notes on the Geology of the Howqua Valley. Min.Geol.Jour. Vic.> 2: HARRIS, W.J. and THOMAS, D.E., Notes on the Geology of the Upper Goulburn Basin. Min. Geol. Jour. Vic. 2 2(3). HARRIS, W.J. and THOMAS, D.E., Upper Ordovician Graptolites from the Rose River, North Eastern Victoria. Min. Geol. J'our. /ic.) Z(5). HILL, D., The Devonian Rugose Corals of Lilydale and Loyola. Proc.Roy.Soc. `f_i. 51: HILLS, E. S., The Geology and Palaeontology of the Cathedral Range and the Blue Hills, in north-we stern Gippsland. Proc.Roy_LSpc.V,i c;. 41: HILLS, E.S., The Upper Devonian Fishes of Victoria, Australia, and their Bearing on the Stratigraphy of the State. Geol.Mag. 68: HILLS, E.S., The Geology of Marysville, Victoria. Geo1.Mag. 69: HILLS, E.S., Records and Descriptions of Some Australian Devonian Fishes. Proc.Roy.Soc.Vic. 48 (2). HILLS, E.S., The Woods Point Dyke Swarm, Victoria, in Sir Douglas Mawson Anniversary Volume, Univ. Adelaide HILLS, E. S., Cauldron Subsidences, Granitic Rocks and Crustal Fracturing in S.E. Australia, Sonderdruck Geo1.Runds. 47: HOWITT, A.M., Phosphate Deposits 'inthe Mansfield District. Bul1.Geo1. Surv.Vic. 46: l-46. JAEGER, H., Two Late Monograptus Species from Victoria, Australia, and Their Significance for Dating the Baragwanathia Flora. Proc.Ro.Soc.Vic. 79: MCDOUGALL, I., COMPSTON, W. and BOFINGER, V.M., Isotopic Age Determinations on Upper Devonian Rocks from Victoria, Australia: A Revised Estimate of the Devonian - Carboniferous Boundary. Bull.Geol.Surv.Arner. 77: SINGLETON, O. P., Geology and mineralisation of Victoria Geology of Australian Ore Deposits, ed. J. McAndrew, Australasian Inst.Min.Met
224 201 TALENT, J.A., The stratigraphy and Diastrophic Evolution of Central and Eastern Victoria in Middle Palaeozoic Times. Proc.RoX.Soc.Vic. 79: TEALE, E. O., Diabases and Associated Rocks of the Howqua River near Mansfield, with reference to th e Heathcotian ' Problem in ' Victoria. ` Proc.Roy;.Soc.Vic. 32: THOMAS, D.E., The Structure of Victoria with res pect to th e Lower Palaeozoic Rocks. Min.Geo1.Jour.(Vic.) l(4); THOMAS, D.E., The Geology of the Eildon D am Project. ' Me;n.Geo1.Su r_v.11. 1'57o THOMAS, D.E. and SINGLETON, O.P., The Cambrian Stratigraphy of Victoria. El ist_ema_cam_l3_rico, su Paleogeografia X el Problema de su Base, t. 2: XX Int.Geol. Cong.Mexico. WHITE, D.A., The Geology of the Strathb ogie ' Igneous Complex, Victoria. Proc. RO osocovico 25'52 Aosog On a Carboniferous Fish Fauna from the Mansfield Distri Ct 9 Victoria. Mem.Nat.Mus.Melb. 1. Wk ' no sa' ;, ; _y, ,r;) -fm,&_'_,'_,v~ ' J. Wflfowilll De//_ R -5`h :ph 'r 1 /, 'tl»._ ffl1fff /- SN<'3V.7`u _l3t,{uf4 l' A. n.howltt - Pfwg. Rep. GQOK. Su/w. Vic., 1877.
225 202 CHAP TER 19 PA.LA.Eozo1c METAMORPHISM A.Np IGNEOUS ACTIVITY OF NORTH-EAST VICTORIA., bv M.D. Leggo and Beavis. 1i1TRoDq_g'r1oN The complex geological history of north-east Victoria during the Palaeozoic reflects repeated sedimentation, orogeny, and igneous activity in the south-western part of the Tasman Geosyncline, within the section of it distinguished as the Lachlan Geosyncline by Packham (1960). Marine clastics of Ordovician age were deposited in this area during the flysch-like phase of the geosyncline. These sediments, deposited under anaerobic, bathyal conditions, form a monotonous, uniform sequence of alternating greywackes, shales and slates. They have undergone mild dynamic metamorphism to a low regional metamorphic grade. Recorded graptolite localities, scattered sparsely through the area, contain late Darriwilian to Eastonian assemblages. _ Middle and Upper Silurian sediments overlie the Upper Ordovician with an angular unconformity in the Wombat Creek area (Talent, 1959; Beavis, 1962). This forms the type area for the Benarnbran Orogeny, a Late Ordovician - Early Silurian deformation which caused severe folding in easternvictoria and south-eastern New South Wales. Metamo rphics The development of an extensive area of schists and gneisses in the region is considered by a number of authors (e. g. Beavis, 1962; Singleton, 1965; Talent, 1965) to be associated with this diastrophism. Two main metamorphic areas are recognized - the metamorphic belt of north east Victoria and the Cooma Complex, further eastwards in New South Wales. In Victoria, the metamorphic belt forms a large tract about 100 miles long and from 4 to 70 miles wide. Joplin (1947) has shown that this metamorphic belt extends in width from Albury to Jingellic along the Murray River, and northwards for an undefined distance (possibly as farias Condobo1in,20O miles to the north). Crohn (1950) and Beavis (1962) have recorded that in the Wombat Creek area Upper Ordovician graptolite-bearing sediments pass transitionally into schists, and it is possible that much of the eastern margin is of a similar transitional nature. It has been established that much of the western margin of the belt has a fault relationship with the neighbouring Ordovician sediments (Beavis, 1962; Leggo, 1964). The rock types within the belt are varied, and schists of the greens chist and amphibolite facies are developed. The schists are often present in zones surrounding areas of gneiss and gneissic granites. These zones, representing varying degrees of metamorphism, have been recognized in a number of localities, e.g. Albury (Joplin, 1947); Wantabadgery-Adelong-Tumbarumba (Vallance, 1953); Corryong (Edwards and Easton, 1937); Kiewa (Beavis, 1962); Barnawartha (Leggo, 1964); Cooma (Joplin, 1942). A chlorite zone, followed by a biotite zone, then a knotted schist zone with the development of andalusite and,or cordierite and finally a high-grade feldspar and, or sillimanite zone, often with some migmatitic characteristics, represent increasing intensity of metamorphism. The rock types ofthe latter zone are referred to here as banded and migmatitic fine-grained gneisses. These are distinct from the relatively homogeneous fine to medium grained 'gneissic' bodies which appear to have some intrusive features as in the core of the Cooma metamorphic complex and in the Huon Creek-House Creek area near Barnawartha. As Vallance (1953) noted for the Green Hills and Wantabadgery Cranites, the gneissic granites and the Cooma and I-luon Creek-House Creek type gneisses associated with the schists often appear to be the product rather than the cause of metamorphism. The metamorphismis a high-temperature, low pressure type. The finegrained, banded, migmatitic gneisses of the metamorphic belt are best represented by the High Plains Crneiss (Beavis, 1962; Crohn, 1950) and the fine-grained 'paragneisses'
226 of Barnawartha-Yackandandah (Leggo, 1964). Chemical evidence suggests an origin for these in-situ gneisses with high-grade schists, without addition of sources. material Examples from external of the gneissic granites are provided by the Corryong, Koetong, Green Hills and Wantabadgery Granites. The metamorphic belts of Victoria both north-eastern (and its extension into New South Wales) and Cooma have the features of Miyashiro's (1961) andalusite-sillimanite type of metamorphic belt. lgneous activity A huge volume of granite sensu lato (granite, adamellite, granodiorite and tonalite) in north-easte rn Victoria occurs and south-eastern New South Wales.. These granites have been classified previously into three groups, gneissic, foliated and massive (Browne,in David, 1950), were each thought which to be of distinctive ages (Ordovician, Silurian and Devonian, However, respectively). variations between all types occur, often in the same batholith, e. g. the Kosciusko Batholith (Moye, Sharpe and Stapleton, 1963) and the Maragle Batholith (Vallance, 1953). major Also and trace element investigations by Kolbe and Taylor (1966) and potassium-argon age determinations by Eve rnden and Richards (1962) have indicated that there is an overlap in chernical both composition and ages of these types. These granites have ages from 430 m. y. (Early Silurian?) to Middle Devonian (Evernden and Richards, 1962; Brookes and Leggo, 1972). Pidgeon and Compston (1965) have determined a rubidium-strontium age of Early or Middle Devonian for the metamorphism at Cooma. The evidence obtained so far points strongly to derivation of the gneisses and gneissic granites from the Upper Ordovician pelites, psammopelites and psammites in the region, with little if any addition of external material. Field VideI1C Obtained by W01'k I`Sin the region supports _a close associationnbetween the meta-sediments and many of the granites cluding gneisses). (in- From comparisons of major element abundances, Beavis (1962), (1942, Joplin 1947) and Vallance (1953) have each shown the probability of at least partial derivation of the granites from sediments in the region. The detailed major and trace element studies of Kolbe and Taylor (1966) led them to consider an origin for the granites of melting and tion mobiliza- of geosynclinal sediments which could be represented by the Upper Ordovician sediments in the region. Vallance (1960) found that in the Wantabadgery-Ade1_on.g-Tumbarumba area the biotites from the granitic rocks and surrounding high grade metasediments had similar compositions. Pidgeon and Compston (1965) have shown that production of the Cooma Granite by anatexis of adjacent metasediments is quite compatible with its Sr87 abundance. The initial Sr87/Sr86 ratio of of th.e Corryong Batholith is also compatible with an anatectic origin (Brooks and Leggo, 1972). It thus seems that areas representing different degrees of melting, permeation and mobilisation of Upper Ordovician metasediments are exposed in northeastern Victoria and south-eastern New South Wales. A sequential record of the major anatectic process involved may well be provided by these areas. lgneous activity in the region may extend beyond the Silurian to Middle Devonian ages found so far by radioactive determinations. At Wombat Creek, north of Omeo, the Mitta Mitta River rhyolites and ignimbrites are ove rlain by a Silurian. sequence, which starts with a massive conglomerate containing rhyolite pebbles in addition to sandstone, slate and granite. The ignimbrites contain xenoliths of granite (Singleton, 1965). The presence of granite in the ignimbrite and conglomerate testify to pre-wombat Creek Group granitic intrusions. Talent (1965, and Ch. 17) also notes that these Middle Silurian Mitta Mitta Volcanics are intrusive into the Banimboola Granite along the Mitta Mitta River north of Eustace Creek. Younger intrusives and extrusives are found in central Victoria, where there is a co-magmatic region of acid intrusives and lavas of known Late Devonian age (Ch. 18). There is stratigraphic confirmation of K-Ar ages deterniined by Evernden and Richards for the Kosciusko Granite, as it intrudes the Middle to Upper Silurian Cowombat Group, and is unconformably overlain by the Lower Devonian Snowy River Volcanics (Talent, 1959). ln north-easte rn Victoria and south-eastern New South Wales, there are a number of crosscutting bodies of leucogranite intruded into either Ordovician sediments or schists and granites. Kolbe and Taylor (1966) have shown that the leucogranites in the Snowy Mountains area are strongly differentiated granites which they regard as an end stage of the same general period 203
227 204 of activity which produced the granodiorite-adamellite batholiths. In north-eastern Victoria the leucocratic Pine Mountain granite (418 f 12 m. y. ) may be slightly younger than the main Corryong Batholith (430 f 8m. y. The.Iemba Rhyolite (409 T 8 m. y.) is only slightly younger, and thus distinctly older than the Late Devonian cauldron Volcanics in central Victoria (Brooks and Leggo, 1972). Mine ralisation in the region is varied but mainly restricted to gold and tin. Both alluvial and reef gold were worked in the Beechworth district. Aurife rous sulphide lodes are common throughout the metamorphic belt, particularly at Bethanga, Mt. Wills, Omeo, Cassillis and Corryong. Cassiterite is found associated both with granites, e.g. the Pilot Range Granite and the Hermit Granite, and with dykes of pegmatite and greisen, e. g. at Walwa, Eskdale and Tallandoon. A limited number of fluorite lodes, often with minor galena, are known, e.g. at Pine Mountain. Molybdenite has been mined at Everton. BEECHWORTH DISTRICT. Introduction. This district is situated on a portion of the boundary between the north-east Victorian Metamorphic Belt and low~»grade regionally metamorphosed Upper Ordovician sediments. An intrusive granitic complex has invaded the Ordovician sediments. Perrriian glacial deposits are found downfaulted into, and overlying, the granite. Extensive erosion has been followed by deposition of large thicknesses of alluvium during the Cainozoic. The area lies on the edge of the Murray Basin and from the highest point, Mt. Stanley (3447 ft. ), the ranges decrease in elevation toward the Basin, considerable variations occurring, depending on both lithological and structural effects. Geology. l. Upper OrdoviciangSediments. Relatively unfossilife rous sediments, consisting essentially of alternating greywackes and shales with minor -_quartz sandstone, black slates and phyllites, form) the country rock neighbouring the metamorphic belt. From the limited fossiliferous localities (Myrtleford, Tungamah and Edi) in this part of Victoria, Upper Ordovician graptolite species have been recorded. The sediments appear to be on the west dipping limb of an anticlinorium or synclinorium. The folding is usually close and inclined and combines bocth parallel and similar elements of folding. The axial planes of the folds have astrike of about 330 and usually dip steeply, but both strike and dip are variable. The anticlines and synclines have rapidly changing plunges and these sometimes reverse over a few tens of feet. The folding is typically non-cylindrical. Multiple deformation in the sediments is a common feature. Beavis (1964) found evidence of three phases of folding in a specimen from Lower Three Mile Creek. At least two cleavages, a slaty cleavage and a strain-slip cleavage, are usually developed in the sediments. 2. The,Metamorphic Belt. Major faulting separates phyllites and low~grade schists from the biotite schists of the metamorphic belt in this district (Loc. 6). Faulting can be traced for about seventeen miles. Rock types within the metamorphic complex even in this limited area are varied Schists of the amphibolite facies are developed; fine-grained gneisses of both sedimentary and igneous origin are wide spread; intrusive bodies of variable composition, structure and texture are common. (a) Schists. Knotted, pinitised, cordierite schists are well developed along the northeastern side of the Indigo Creek Valley (Loc. 5) but occur elsewhere in the are'a only to the north and north-west of Albury. In the Commissioner s Creek area the schists are of finegrained biotite grade and interbedded psammites and pelites are readily distinguishable. Knots appear to have been developed in the pelitic strata only to be obscured by shearing forces related to the neighbouring crush zone. From Barnawartha a belt of schists extends in a north-easterly direction to Albury. These schists are predominantly psammitic and psammo-pelitic and banding is absent. The pelites, where they occur, form biotite-sillimanite schists (Loc. 4). (b) Fine grain<>d gneisses, A distinction is made between gneisses, paragncisses and orthogncisses. The gneisses are d<»s<irib<>d below for the I-Iuon's Cr<» ~k - House Crcvk area. This body is thought to be analagous to the Cooma Grzmitv and, although <~h<~mically vvry similar Fig. l (opposite). Geological map of the 3eechworth District.
228 T. '+-. ' ]&-.,' S«f,iMnlary Rocks TERTIARY to RECENT E::J AII,_ ~ P...O' PERMIAN ~ GkJCtat~.. UPP R ORDOVICIAN ~ H igh QrOde ~R DEVONIAN Ign#Ous Racks GoldIn eol Slkltled Zone 8yowatho ApI [±:±] P' R_ G<... 1'+. +. I Polo! -.. G<.. it., q-,z-tou,_- '-'10 plio.. ~ MwrMUn9H ac..tn Granite UIIIIIIa Sto'*y Gronit. (#- A- f '-'den '.. it. A - A '' [E] E Mrtotl Hat-nb1eft4e Parphynt. C!:::!J E_ Quortz ''...,..... POST - ORDOVICWII GnetI$C..'z ~ mca diorite,00 -GMIotcai _, ciohno!. Goo~ca1 _,.''''_ GooIo9iCof -, -...' Li... it.. ~t~ Location no. ICALI OI-.EI Trock Roilwoy
229 to the enclosing metasediments, may have been intrusive. The paragneisses schists) (high-grade are those derived from the sediments by metamorphic differentiation, and, though of different types (banded, migmatitic, porphyroblastic), have transitional boundaries (Loc. 3) with the schists and appear to have formed in-situ. The orthogneisses are small, intrusive igneous concordant, bodies which have sharp contacts with the schists. They occur primarily in the schists and in banded migmatitic gneisses (paragneisses) along the Indigo Creek valley along and Kookaburra Creek and Fell Timber Creek. The fine-grained paragneisses related in are closely type, origin and probably age to the High Plains Gneiss (Crohn, 1950; Beavis, 1962) which forms the core of the metamorphic belt in the Omeo and Kiewa areas. In the Huon's Creek - House Creek area, the gneisses are relatively homogeneous and remnant bedding cannot be distinguished. These gneisses are fine grained, biotite rich, and show a well-defined foliation (Loc. 2). They are also typified by biotite-rich schlieren, partly fibrolitised, often and by feldspar, quartz or rarely sillimanite porphyroblasts. The major constituents are biotite, quartz and feldspar, with lesser muscovite, cordierite, pinite, manite silli- and minor schorlite, apatite and zircon. In the Comrnissioner's Creek area, the paragneisses are finely banded and, particularly in the headwaters of Commissioner's Creek, have pegmatitic porphyroblasts. Major logical litho- differences remain, i. e. different beds are recognisable on a broad scale, but the identity of smaller units is lost. Sillimanite is locally developed but cordierite and, or appear pinite to be lacking. Considerable recrystallisation and varying degrees of metamorphic differentiation can be recognised (Loc. 7). To the north the Baranduda Range is composed of a quite different type of gneiss, characterised by the virtual lack of foliation, euhedral crystals of quartz, feldspar and biotite, minor pinite, and a high silica content. The orthogneisses are fine-grained rocks with a gneissic foliation caused by parallel orientation of the micas (Loc. 4). The orthogneisses contain less biotite than the paragneisses but are slightly coarser grained and have more feldspar and muscovite, Biotite schlieren are less common than in the paragneisses and phenocrysts are not abundant. The Albury Gneiss of Joplin (1947) is thought to be a highly contaminated orthogneiss (Loc. 1). (c) BarnawarthaGneissic Granodiorite. Afoliated, medium-grained, granodiorite biotite-rich has been intruded as numerous lit-par-lit leaves into schists in the area forming The Kookaburra, near Barnawartha (Loc. 4). Interleaved with the granodiorite, usually in a parallel fashion but sometimes cross-cutting, are abundant younger pegmatites and (or fine-grained orthogneisses foliated pegmatites). (d) Yackandandah Basin Granite. The Yackandandah Basin Granite is a. large batholith composite which forms low country extending from Al1an's Flat to Barwidgee to the south. It has intruded both metamorphic rocks (schists and fine-grained gneisses), and Ordovician sediments. The batholith is elongated in a me ridional direction. The main rock type in this batholith is a coarsely porphyritic biotite granite in which poorly aligned euhedral feldspar phenocrysts are well developed (Loc. 9). (e) Gneissic quartz-mica diojrite. Gneissic quartz-mica diorite outcrops in Middle Creek, in Commissioner's Creek and in Yackandandah Creek. The Commissioner's Creek been intruded diorite has concordantly into the metamorphic rocks (Loc. 8). (f) Pegmatites. Pegmatite sills have intruded the schists in the Commissioner's area, Creek the Indigo Creek area and between Barnawartha and Wodonga. They are most abundant in the latter area, particularly in the vicinity of the Barnawartha Gneissic Granodiorite (Loc. 4). They are usually absent from the fine-grained gneiss areas, except in the vicinity of this g ranodio rite. (g) Structure. Bedding, schistosity and foliations are usually parallel, an exception being the Barnawartha schists in which a discordance between schistosity and bedding is common. With transitional boundaries between the schists and gneisses, structures are traceable across the strike from one rock-type into the other. The strike of the foliation varies fairly uniformly from 3200 at Commissioner's Creek to at Barnawartha. Seve ral major faults transect the area. The Sawpit Gully Fault (Loc. 9) and the Indigo Creek Fault are crush--zones which separate the metamorphic belt from the relatively unaltered Ordovici
230 Z06 sediments. These two structures are probably part of the same fault zone but have been separated by displacement on a later fault, the Beechworth Fault (Loc. 6). 3. Upper Devonian lntprusive Complex. An intrusive complex consisting of three separate granites (Loc. 3_1 & 36), adamellite (Loc. 34), granodiorite (Loc. 35), granodiorite porphyrite and hornblende porphyrite has been intruded into strongly folded Ordovician' sediments in the Beechworth district. These intrusions are believed to form a cogenetic suite. The order of intrusion of the Beechworth complex is uncertain but is thought to have been that of decreasing basicity, i.e. granodiorite followed by granodiorite porphyrite, adamellite and granites. The complex probably constitutes a post-deformation intrusive cycle with emplacement low in the epizone. Emplacement was by means of both major and piecemeal stoping, and also in part by plug intrusion. The complex intrudes Upper Ordovician?rocks and is overlain in places by glacials of Lower Permian? age, but a more exact age cannot be ascertained stratigraphically. A potassium-argon age of Upper Devonian was obtained by Evernden and Richards (1962, p.43), but is suspect because of weathering of the sample. However, their work shows that the complex cannot be younger than Upper Devonian (ibid., p. 3). Physiography. The area, as a whole, has only moderate elevation and a number of planated, dissected areas of differing elevations occur, corresponding to differences in lithology. To the we st and northwe st the area is bounded by alluvial plains. The metamorphic rocks usually have an elevation greater than that of the intrusive complex. The Ordovician sediments show considerable variation in elevation forming low hills to the north and high, well-dissected country to the south, in the vicinity of Mt. Stanley. An exceptionally well-developed basin structure marks the position of the Murmungee Basin Granite. The Yackandandah Basin is also located in granite. Jointing has controlled the drainage pattern in the Pilot Range and Stanley Granites, as evidenced by the angularity of stream courses. The Indigo Creek valley has been developed along a fault zone, whilstithe course of the Middle Creek has been determined by faulting (the Beechworth Fault), and by the resulting differences in lithology on either side. Faulting has also been responsible for the aberrant drainage direction between Beechworth and the Buckland Gap. Commissioner s Creek and upper Indigo Creek and its parallel tributary have been developed parallel to the foliation of the gneisses. Structures partly control drainage in the Ordovician sediments, e. g. faulting for Kneebone's Gully, and jointing and bedding for Magpie Creek. Jointing and diverse litholgies have controlled the course of Hodgson's Creek. Faulting has probably been responsible for the formation of the Wangaratta 'graben', whilst faulting combined with different lithologies controlled the erosion forming the Wooragee Basin. Tl-l E CORR YONG DISTRIC T, Introduction. The Corryong District forms the area enclosed by the great bend in the Murray River. It consists of a deeply and irregularly dissected tract of mountainous country, with drainage mainly to the north, into the Murray River. Following the deposition and folding of the Upper Ordovician bedrock metamorphism and igneous activity occurred during the' Silurian and Devonian. With the exception of the extrusion of Upper Eocene basalts just to the north of the area (at Tumbarumba and Kiandra in N. S. W, ), subsequent activity has been restricted to earth movements (e. g. the Kosciuskan uplift), denudation, and deposition of alluvium. Geology. l. Upper Ordovician sediments. These form the olde st rocks exposed in the area and although replacedby schists and granites in the north they are wide spread in the south. The principal lithologies are greywacke and shale or slate. Interbedded with these main rock types are minor sandstones and carbonaceous slates. T.S. Hall (1902) examined some of the graptolites collected from the latter and concluded that they were of 'Late Ordovician age. Faigly intcense folding has produced steeply dipping beds which have a variable strike, usually The variability in strike is the result of marked plunging of the folds. Fig. 2 (opposite). Geological map of the Corryong District.
231 GEOLOGICAL MAP CORRYONG DISTRICT INCLUDING PORTIONS OF NORTH-EAST VICTORIA AND SOUTH - EAST NEW SOUTH WA LES 6 Kilom.+~.s ~2~~O ~2~~5+ -z4~~' Sedimentary Rocks QUATERNARY I~ AlllMum, sand,qrovel, silt ~ Sondstone,shole, slotf', qreywocke /gneolls and Metamorphic Rocks EOCENE OLDER VOLCANICS L.1_v...!.._v~1 Basalt Leuco - qronite. granite SILURIAN l1li I~I MITTA MllTA RIVER ~ VOLCANICS Rhyolite I IQnimbrite Porphyries, dolerite, diorlte, Qranophyre, muscovite Qranite. Rhyodacite, with minor rhyolite, tuff, aqqlomerate and sediments I i & i I I Gt-anit. I 9ranodiorite Metamorph i c [ HiQh Qrade schists, Qnei.. Schists of lower Qrade GoaIOCJical boundary HiQhway Main connectin9 rood Other roads Troc.k Railway Co'piled D, II. D. LE6GO Date : JULY I' Location
232 Schists. Schistose aureoles occur around the Corryong and Koetong Granites. The former( have been developed from the Upper Ordovician sediments in the progressive sequence of shales and greywackes, phyllites, micaceous schists and nodular schists (in places containing andalusite» e.g. in the steep range to the east of Thowgla Creek). The width of the aureole varies from a fewfeet to more than a mile (Loc. 4). 3. The Corryong Granite. This is an extensive body of grey granite forming part of the Maragle Batholith. The latter is a composite batholith elongated in a NNW direction and extending well into New South Wales. Variable chemical compositions and textures are a feature of the batholith. Analysed specimens range from granite to granodiorite in composition. A foliation due either to a gneissic banding (Loc. 15) or to the parallel orientation of feldspar phenocrysts is quite frequently observable. There appears to be a close similarity between the Corryong Granite and the Green Hills and Wantabadgery Granites, components of the Maragle Batholith mapped by Vallance (1953). From the limited field work done by the writer and by Vallance, it appears that the Corryong Granite is continuous into the Green Hills Granite. All are intrusive into zoned schists, including andalusite schists, but have a somewhat diffuse contact and have previously been described as a product of the metamorphism. It is suggested that the Corryong Granite has not been extensively mobilised. The presence of cordierite in some thin sections point to a high degree of contamination if the granite has not, in fact, been derived from the schists themselves. Xenoliths are common in the Corryong Granite and are usually present as biotite-rich clots, often rather elongated. Large xenolithic blocks and roof pendants are not uncommon (Loc. Stanniferous pegmatites, greisens and quartz veins are associated with the granite (Loc. 14). The principal phases of the Corryong and Koetong granites are indistinguishable chemically and petrologically, and they have a Rb/Sr isochron giving an age of 430i 8m. y. (Brookes and Leggo, 1972). 4. _ _oun_g_er intrusives and extrusives. (a) The dyke swarm. A swarm of approximately 850 dykes of granite, porphyry, porphyrite and dolerite occurs in the_corryong area. There are two strong concentrations of these dykes about the latter granitic intrusions of Pine Mountain (Loc. 16) and Mt. Mittamatite (Loc. 17). About 500 of the dykes are of porphyry and porphyrite and about 300 are of dolerite. The former are frequently over a mile in length. The earliest dykes intruded were the granite dykes _which are fine-grained, white, muscovite-rich bodies, relativelynrich in tin, and probably related to the Corryong Granite. These were followed by the porphyries (including granophyric varieties) and porphyrites. Lastly, the dolerites (Loc. 17) were intruded, often forming composite bodies with the porphyries and porphyrites. Metasomatic alteration of the dyke rocks is quite marked, particularly in the dolerites, where pyrite and carbonate are often developed. (b) The Jemba Rhyolite This extrusion of rhyolite and ignimbrite forms a roughly elliptical mass having an area of about Z5 square miles. It is over two thousand feet thick (Loc. 19), and overlies an eroded surface of both Ordovician metasediments and Corryong Granite; at two localities underlying river gravels are also found. A ring dyke of encircles porphyry the rhyolite (Loc. 18) and from this and the high elevation of the associated leucogranites of Pine Mountain and Mt. Mittamatite compared with the rhyolite pile, it is clear that subaerial cauldron subsidence has taken place. A Rb/Sr age of m. y. for the rhyolite shows that this event appreciably predated the Upper Devonian cauldrons in central Victoria. (c) Leucogranites of Pine Mountain and Mt. Mittamatite. The se form two intrusive stocks in the _Corryong Granite. They are both highly differentiated, leucocratic, red granites which Kolbe and Taylor (1966) have grouped with the leucogranites of the Snowy Mountains area. They consider 3
233 208 this group of granites to represent differentiated products of the same magma that produced the large granodiorite batholiths. Rb/Sr ages of 418'f 12 m. y. (Pine Mountain),and 427 1' 32 m. y_. (Mt. Mittamatite) group their intrusion with that of the Corryong Batholith. However while the the initial Sr87/Sr 6 of of the Corryong granite is consistent with the anatectic origin suggested by its composition, the extremely low initial Sr87/Sr86 of of the Mt. Mittamatite granite suggests a magma of subcrustal derivation. Physiography. The Corryong district lies on the south-western side of the Kosciusko Plateau, where the latter is sloping down into the Eastern Highlands of Victoria. Edwards and Easton (1937) consider the area to be fan-like, with creeks and interfluves radiating from the high country surrounding Mt. Gibbo (5, 763 ft.) further south. The drainage system is controlled by faulting, the strike of the sediments and jointing in the granites. The principal creeks drain northwards into the Murray River and extensive river flats along these provide rich agricultural land. The prominent physiographic lineament of Cudgewa Creek is believed to be due to fault control._ Peaks in the area include Pinnibar (4,100 ft.) in the south, Mt. Cudgewa (3, 575 ft. ), Mt. Burrowa (4, 181 ft. ), Mt. Mittamatite and Pine Mountain. Mt. Pinnibar, and Mt. Gibbo further south, are in folded sedimentary rocks of Ordovician age. Mt. Cudgewa lies on the boundary between granite and_ metasediments, Mt. Burrowa is a plateau of Jemba rhyolite, and Mt. Mittamatite and Pine Mountain are approximately conical bodies of fine-grained red leucogranite. Small hills in the vicinity of Corryong, as well as the more prominent ridges, are often due to the increased resistance to erosion of porphyry and porphyrite dykes and plugs. Between Walwa and Tintaldra, particularly on the northern side of the Murray River, these dykes are readily discernible as walls across the hills. KIEWA AREA, Introduction. The Kiewa Area lies on the western margin of the Metamorphic Complex. The topography is rugged, the terrain thickly vegetated, and the rocks deeply weathered. Exposures, except on the higher areas, are extremely poor. The elevation varies from 1,200 ft. at Mt. Beauty township to 6, 509 ft. at the summit of Mt. Bogong. Rocks ranging in age from Upper Ordovician to Recent occur in the area(fig. 3). The youngest of the Palaeozoic rocks are epi-middle Devonian, and the oldest of the Cainozoic rocks are Oligocene. The period from epi-middle Devonian to Oligocene was apparently one in which erosion was the only active geological process. Ge ology. 1. Hotham Slates (Upper Ordovician): Slates, greywackes and quartz sandstones occur in the southwest of the area. Slates predominate in the area proper, but, to the west, greywackes become more important. Graptolites of Upper Ordovician age have been recorded from Myrtleford, and are the sole basis for assigning this age to the slates. In the Harrietville- Hotham-Feathertop sector there is clear evidence of two generations of folds: the first generation (F1) structures are large, similar style folds; the F2 folds are relatively small (Loc. 30). Locally, adjacent to major faults, a third generation of folds has been superposed. 2. High Plains Gneiss and Mt. Nelse Schist. The schists and gneisses of the Kiewa area are faulted against the Hotham Slates, the boundary being formed by the West Kiewa Thrust Zone. Along this zone, slates or low grade phyllites and schist abut against high grade quartz-felsparsillimanite gneiss. The zone itself, about 1 mile wide, is largely mylonitised schist and gneiss. The Mt. Nelse Schists are medium to high grade, rich in biotite and cordierite, and often knotted. They are transitional westwards into the High Plains Gneiss, and eastwards to low grade chlorite schists, phyllites and slates. The southern boundary on the High Plains is formed by the Nelse Fault, a sinistral wrench structure. The High Plains Gneiss (Loc. 27), which forms the core of the metamorphic complex, is a strongly banded migmatitic cordierite-sillimanite gneiss, referred to (Beavis, 1962) as 'permeation gneiss'. The composition and texture of the gneiss varies greatly.
234 /.'._~:::.. ;_ :':..:....I <//» _ 1'. / _ * MTIQOGONG L. f (. //..:.:1.f. < af' $ v/ 912.;:. MT = Aurv - -V /f H / &.225 -_ ;//` / »- Y,. M,//~,_ ],z J& A-;tE;f'.»'- (' {} E3M{ fr»/ / rg»_ / Q I ( ` L / ' i / i_ if i ' / A»»». / 45; f`~l ('// -F* ~ ' ep ee '` ` '+ + I _,L.`>H ` mv V-Jné H1LL 'P / v * `7`/e] ' '/j-=- U4 < uf J, iiiiiii/+ +1 ` Q ' +++++%~++} ` ` / ` r + / IP* g / ` ' U -»» 5.L 4. +( ` T ~ /.~ ~ ++ #iw Q -» f J/ L ` / +4-ii +'L+ / 'f - ' n%}g/»~ iq' ' i +.L / :i.,. W M + ii i F.;.-af 'i _ X <5 / f 'H i!1{ }!1 i mll / {MTF A lmfn) 111; _ Je / X - H M T A'Jm li + I H/ 7 _ <i il 2 5 ' ' Lb/ rc: + i1 iif. +?.+ ) W /// / I+~ #RQ /53» if *fe if f%$ E?, ff ,~_='' 45 /' I ;=» I E ~=» iw 4` -<- if :i;t W _ f/ ee / f Q 45 , t 7 'W / 39 / I dz* I' 'I (lf /.,' * =f ' Y Nil-G H A, ui im g T; q?/é,/'7'.: g?f< lf <i &:?` ' ~ +++'f-*_+ '1->V v v v v ' / /»W Q i, QV KJV. V / 5;_,; v -f t;-_:~ lvfwtn,uufwuu if ' L ;%s~s.,&' ~'= vv v v v v v v v v v/ L OLIGOCENE fl' fvv v v v v v v,.v._v»j *~}- ' %f_ Vf C'' ' ` + T v v + A RfCENT,'u! w F; V V U -_ W / //'Ml ~ :::::: ' il# / H.Y v v v *O - :ml/,;'l2l K / * /,V V! // ` {~ J, % / ~ in ' 7. ` i. msn/ _, I / lr HH //(VV V/?LW W/ ' {6NWw W 'G 'U gl? EMA'/? y ~'?,` ` & ll N ur /vast scwsr I//,W (5-Hy, ~ zs:>,2 :;2s;;~ if f up Y r Tl 4/ raul;0-:':s;on_ca;»;a rgauzqirn encc/;t:'r 7:, F GNL'/SSIC cawvoo/on/rc ='>,2: z 2::2; ;~ -,5, E rnotmu hp' i caracm.as~r c nocns mlmmum :ou/mon `BEDUNG 4 1-nano Lancs --_L_ V (/ iwh _ Mats VV; 4e f'e m Fig. 3. Geological map of the Kiewa area (Beavis, 1962).
235 210 Within the Kiewa Area there is no clear evidence of the age of the schists and gneisses. They have been derived from the Upper Ordovician sediments, and are considered Benambran. It is of interest that there is, as yet, no convincing evidence of more than one deformation of these metamorphics, except on the margins. 3. Kiewa Crranodiorites. These intrusives are considered, on slender evidence, as Bowning. They are intrusive into the Ordovician sediments, the schists' and the gneis ses, on all of which they have imposed a thermal metamorphism. Gneis sic granodiorites (Loc. 28) have been interpreted (Beavis, 1962) as due to intrusion under stress. Locally, the granodiorites have been sheared and recrystallized, and associated with them are several large masses of recrystallized aplite (e.g. Round Hill, Tawonga, Mt. Bogong, Pretty Valley). 4. Big Hill Quartz Diorite. Quartz diorite, and related lamprophyre dykes, intrude 'Ch _gh 5~SSeS and the granodiorites. It is believed that the higher levels, where schlieren and other flow structures are abundant, represent the roof of the pluton. The quartz diorite is a coarse textured plagioclase-hornblende-biotite rock, in which the hornblende is invariably idiomorphic. Quartz is present only in small proportions, but is an essential constituent. On the margin of the quartz diorite,alkaline syenites are locally weakly developed, possibly as a late phase) differentiate. The related lamprophyre dykes (Loc. 2.3) are abundant throughout the area, intruding all other rocks, although overlain by the Tertiary sediments and volcanics. They vary in thickness from a few inches to over 100 ft., but all have a more or less common trend between E-W and 2005 of E. The dykes and the quartz diorite are tenatively considered Tabberabberan. 5. BogonggVolcanics. Basalts, limburgites, and phonolites, with associated doleritic and alkaline dyke s,occur on the Bogong High Plains (Loc. 26) and near Mt. Hotham. Tuffs are associated with the flows which overlie fossiliferous sands, clays and gravels, sometimes with thin seams of brown coal. The maximum total thickness is 500 ft. Because of the intimate as sociation_with Oligocene plant beds, the extrusives have been correlated with the Older Volcanics of Victoria. Points of eruption have been recognized at Howman s Gap, Roper's Lookout (Loc. 25), Dibbin's Flat, Mt. Smythe, and Ruined Castle, where agglomerates and basalts occur as plugs. 6. Alluvial Deposits. The Tawonga Gravels are preserved in mature valleys on the Bogong High Plains, and in the lower Kiewa Valley, where they have a thickness of up to 200 ft. Recent deposits cover these in part and include peat beds up to 5 ft. thick. Structure Little is known of the folding of the metamorphic rocks, since some uncertainty exists concerning the nature and origin of the foliation. It is clear that the slates and phyllites have suffered two folding deformations, and locally three. The crystalline high grade schists and gneis ses appear, however, to have suffered only one such deformation and may have represented a stable block during later foldings. The main fold structure at Kiewa is visualized as a large, gently north plunging anticline, the hinge zone of which is occupied by the permeation gneiss, and the we ste rn limb of which has been sheared out on the West Kiewa Thrust. Faults dominate the structure: these are shown on Fig. 2. The more important are the Tawonga Fault (Loc. 20), a low angle thrust, in which the Tawonga Gravels were involved (Beavis, 1960), the We st Kiewa Thrust which here forms the we stern boundary of the Complex, and the Nelse Fault, along which the schist-gneiss transition has been displaced laterally some 14 miles. The Tawonga Fault is responsible for the 'embayment' in the schist-sediment transition in the Mountain Creek - Mitta Mitta area, and the movements on this fault for the general elevation of the area to the south east. Physioggraphy. Beavis (1962) and Crohn (1950) have shown a general accordance of peaks in the region at about 6, 000 ft. It is postulated that the area consisted of a peneplain which, due to movement on the Tawonga Fault, as well as other parallel faults, led to rejuvenation. Uplift was accompanied by doming of the surface so that stream capture is a feature of the drainage pattern in the
236 211 area. The High Plains are a remnant of the peneplain. That uplift was intermittent is shown by the valley in valley' structure, benches being developed in the main valleys at 5800, 5000, 4000 and 3600 ft. The stream pattern in the area has been controlled largely by structure. Streams have tended to develop on faults, so that some prominent lineaments have been formed. The more notable of these are the lower Kiewa valley and the We st Kiewa valley. The stream system throughout the area is markedly rectangular. The topography was not affected by Pleistocene glaciation, no evidence of which has been found in the area, although periglacial phenomena have been noted. IT INE RAR Y Localities are shown on Figs. 1, 2, and 3. The Wangarattta and Tallangatta 1:250, 000 topographical sheets (National Mapping Division, Department of National Development) are excellent road guides for the area. FIRST DAY - Albury-Tallangatta (Beechworth District), Locality 1. Monument Hill - Albury Gneiss. Locality 2. House Creek - Gneiss. Locality 3. House Creek - Transition between schists and gneiss. Locality 4. Barnawartha - Gneissic granodiorite, orthogneiss, pegmatites and schists. Locality 5. Indigo Creek valley - knotted schists. Locality 6. Head of Indigo Creek valley - gneis ses, schists and phyllites, Indigo Creek Fault, Beechworth Fault. Locality 7. Baranduda television 'tower - gneisses, overall view of topography. Locality 8. Commissioner's Creek - gneissic quartz-mica diorite. Locality 9. Twi_st's Creek - Sawpit Gully Fault, Yackandandah Granite.» SECOND DAY - Tallangatta - M_t. _Bea_uty, via Cor_r_yon_g (Corr_yong _District_2.i Locality 10. Murray Valley Highway, immediately S of Tallangatta - gneiss. Locality 11. Eskdale turnoff from Murray Valley Highway - adamellite in road cutting. Locality 12..Murray Valley Highway, 3m. N of Koetong turnoff - Koetong Granite. Locality 13. Murray Valley Highway along Murray River, 4m N of Granga - foliated Koetong Granite Locality 14. Walwa - tin mine. Locality 1-5. Walwa - Corryong Granite. Locality 16. Pine Mountain -.porphyry dykes and Pine Mountain leucogranite. Locality 17. Mt. Mittamatite - raft of schist in Corryong Granite, dolerite dyke, Mt. Mittamatite Granite. Locality 18. Cudgewa - porphyry ring dyke. Locality 19. South end of 'The Bluff' -.Iemba ignimbrite and rhyolite. THIRD DAX - Mt. gbeauty - Mt. Beauty (Kiewa. Areal. Locality 20. West Kiewa River near Mt. Beauty Chalet - Tawonga Faul_t. Locality 21. Roper's Track Lookout - geomorphology Locality 22. Pretty Valley Bridge - Kiewa Granodiorite. Locality 23. Upper Kiewa Valley' Road at Robbers Roost turnoff - lamprophyre dykes in road cutting. Locality 24. Fall's Creek - contact zone. Locality 25. Roper's Lookout - older volcanic neck. Locality 26. Ruined Castle - basalt. Locality 27. Mt. McKay - High Plains Gneiss. Locality 28. Pretty Valley - gneissic granodiorite. Locality 29. Bundarrah River - basalts overlying brown coal. FGURTH DAY - Mt. Beauty ~ Beechworth - Melbourne (Beechworth District1)_. Locality 30. Symond's Creek Road - F2 folds in low-grade schists in cutting at third bridge from Tawonga South (Beavis, 1968), Locality 31. Chiltern turn off, near Beechworth - Pilot Range Granite. Locality 32. Beechworth - Newtown Fault in granite at Spring Creek.
237 212 Locality 33. Falls - alluvial workings of Pennyweight Flat. Locality 34. Golden Ball - adamellite. Locality 35. Everton - molybdenite mine - granodiorite. Locality 36. Murmungee - Murmungee Basin. Locality 37. Melbourne or Eldorado -A gold-mining dredge. Locality 38. Clear Creek - quartz-tourmaline nodules in Pilot Range Granite. Byawatha aplite bodies. REFERENCES Beavis, F.C The Tawonga Fault, North-East Victoria. Proc. Roy. Soc. Vict.z_;72~: Beavis, F.C., The Geology of the Kiewa Area. Proc. Roy. Soc. Vict., 75: Beavis, F.C., 'Superposed folding in the Beechworth Contact Aureole. PIOC. RQY. SOC. Vict., 77: Beavis, F. C., Structures in schist, Tawonga, Victoria, Australia. Proc. Roy. Soc. Vict., 81: Brooks, C. and Leggo, M. D., The local chronology and regional implications of a Rb-Sr investigation of granitic rocks from the Corryong district, southeastern Australia. Journ. Geol. Soc. Aust., 19: Crohn, P. W., The Geology, Petrology and Physiography of the Omeo District. Proc. Roy. Soc. Vict., 62: David, T.W.E., The Geology of the Commonwealth of Australia. Arnold, London. Edwards, A. B. and Easton, J.G., The lgneous Rocks of North-Eastern Benambra. Proc. Roy. Soc. Vic.,_ _0 (1): Eve rnden, J. F. and Richards, J. R., Potassium-Argon Ages in Eastern Australia. Jour. Geol. Soc; Aust.79 (1): Hall, T.S., Reports on Graptolites. Rec. Geol. Surv. Vict.,l_(1): Hills, E.S., 1959.' Cauldron subsidences, granitic rocks and crustal fracturing in S.E. Australia. Geol. Rundschau,f17 (2): Joplin, G.A., Petrological studies in the Ordovician of New South Wales. I. The Cooma Complex. Proc. Linn. Soc. N.S.W., 67: Joplin, G.A., Petrological studies in the Ordovician of New South Wales. IV. The northern extension of the northeast Victorian metamorphic complex. Proc. Linn. Soc. N.S.W., 72: Joplin, G.A., An apparent magmatic cycle in the Tasman Geosyncline. Jour. Geol. Soc; Aust., 9: Kolbe, P. and Taylor S.R., Geochemical Investigation of the granitic rocks of the Snowy Mountains Area, New South Wales. Jour. Geol. Soc. Aust., 13 (1): Leggo, M.D., Unpublished M.Sc. The sis.' Geol. The Geology of the Beechworth District. Dept. Univ. of Melbourne. Evolution of metamorphic belts. J. Petrology, 2_ Miyashiro, A., Moye, D. G., Sharp, K. R., and Stapleton, D. H., Geology of the Snowy Mountains Region. Geological Report of the Snowy Mountains Hydro-Electric Authority, Cooma, No So We Packham, G.H., Sedimentary history of part of the Tasman Geosyncline in South-Eastern Australia. Rep. 21st Int. Geol. Congr., 12: Pidgeon, R.T. and Compston, W., The age and origin of the Cooma granite and its associated metamorphic zones, New South Wales. J. Petrology, Singleton, O. P., Geology and mineralization of Victoria, in Geology of Australian Ore Talent, J.A., Talent, J.A., Deposits, Second Edition. Notes on Middle Palaeozoic stratigraphy and diastrophism in Eastern Victoria. Min. and Geol. Jour.,6 (3) : The stratigraphic and diastrophic evolution of Central and Eastern Victoria in Middle Palaeozoic Times. Proc. Roy. Soc. Vict., 79 (1): Tattam, C.M., The metamorphic rocks of North-East Victoria. Bull. Geol. Surv. Vict.,52. Vallance, T.G., 1953 Studies in the metamorphic and plutonic geology of the Wantabadgery-Adelong Tumbarumba district, N.S.W. Proc. Linn. Soc. N.S.W.,78: , Vallance, T. G., Notes on the metamorphic and plutonic rocks from the Wantabadgery- Adelong-Tumbarumba district, N.S.W. Proc. Linn. Soc. N.S.W., 85:
238 CHAPTER Z0 Z 13 THE RIVERINE PLAIN IN NGRTHERN VICTORIA bv J.M. Bowler and P.G. Macumber 1NTRoDUc'1 1oN, Aggradation of the Rive rine Plain occurred through the Quaternary Period, with widespread deposition of a thick sequence of sands and clays from prior streams flowing inland from the highlands. The Quaternary sequence recognized in the Riverine Plain particularly from pedological studies has recently been formalized by Lawrence (1966) as the Wunghnu Group, divided into: Coonambidgal Formation (seve ral alluvial phases) Mayrung Member (alluvial) Widgelli Member (aeolian) Shepparton Formation Quiamong Member (alluvial) Katandra Member (alluvial) Kialla Member (alluvial) Deposits of the Riverine Plain and associated geomorphological features of two areas will be discussed - the Loddon Plains and the Echuca-Shepparton area. A. THE LODDON PLAINS (P.G. Macurnber) The members of the Shepparton Formation outcrop on the Loddon Plains near Serpentine, often as terraces within the highlands passing into a layered sequence in the plain. Katandra Member. The pedologically well-organized grey clays of the Katandra Member outcrop only along incised streams. In the banks of the Loddon River and Bullock Creek they underlie younger Quiamong sediments. No coarse sediment has been found in outcrop, however the widespread sands about 30 ft. below the plain near Serpentine may be Katandra channel deposits. Quiamongg Membe_r_. The Quiamong Member sands and sandstones grade upwards into sandy silts and clays. Deposition from prior streams in channel levee and flood plain environments caused rapid lateral. variations. The sands are generally cemented by clay and sometimes carbonate, the latter often infilling vertical joints in channel deposits. The thickness of this unit varies, being greatest nearer the highlands and becoming thinner with finer grain size northward across the plain until it is predominantly clay. Maximum observed thickness is 40 ft. in the highlands near Laanecoorie, where it contains abundant plant remains towards the base. It outcrops extensively along Bullock Creek east of Bridgewater, in the banks of the Loddon River, and as an aggradational unit in the Korong bahada, at the foot of low granitic hills west of Serpentine. The form and shape of the Quiamong stream channel, which may often be found within a few feet of the surface, is generally not detectable at the surface having been completely blanketed by the overlying aeolian Widgelli Member. Widgelli Member. The clayey Widgelli Member extends across most of the area from the Mallee to the eastern margins of the plain. It outcrops extensively in the Se rpentine area; nearer the highlands it blankets Ordovician sandstones and slates, Newer Basalts and Quaternary sediments. It is a red-brown calcareous clay to sandy clay thought to be aeolian, rarely exceeds a thickness of three feet, and from its uniformity and recognizable characteristics provides ia marker horizon, as in the Serpentine-Boort area. Mayrung Member. The Widgelli clays are overlain in part by prior stream sediments, on the Loddon plains deposited as a large alluvial fan with its apex near Serpentine. Sediments in
239 214 the fan represent channel, levee and flood plain deposits; in places the levee systems have been aggraded up to 15 ft. above the general level of the plain. This fan gradually fades out to the north. SE DIME NTATION. On the Rive rine Plain in Victoria streams flowing westerly from the Eastern Highlands deflected north of the three topographic highs of the Heathcote-Colbinabbin Range, the Te rrick Terrick Range to the north-we st, and, further west, the Gredgwin Ridge from the northern end of which, near Lake Charm, high ground of a line of lunettes continues to the Murray R. Hence no fluvial material from the watersheds east of the Colbinabbin Range have been incorporated in the Quaternary sediments south of a NW-SE line joining the northern limits of these highs. This southerly limit is approximately delineated, between the Te rrick Terrick Range and the Gredgwin Ridge, by the course of the Pyramid Creek which there flows along an ancient course of the Goulburn River. The significantly different sedimentation patterns south of the Terrick- Gredgwin Ridge line, and the deflection of north-flowing streams on crossing this line into the influence of a weste rly flowing depositional system, is taken to mark the northern boundary of a distinct we ste rn physiographic sub-province of the Northern Plains ofvictoria. Whereas sediment immediately to the south of the Pyramid Creek was deposited in a predominantly far flood plain environment, that to the north was laid down in a prior stream landscape as channel, flood plain and levee deposits. The Loddon R. is the most westerly river reaching the Murray River from the south. In the Central Highlands the Loddon R. is restricted to a single wide course meandering across a confined floodplain. On entering the plain there is a decrease in gradient, with deposition of sediment and development of_a complex system of channels. This has prevailed throughout late Quaternary times with the plain being systematically aggraded by climatically governed cycles of fluvial sedimentation. Grain size of the sediments decreases northward across the plain until only fine suspended material is carried, to build up a predominantly clay plain. The last major phase of prior stream activity, the Mayrung phase, formed a large delta-like alluvial fan with its apex near Serpentine and extending twenty miles out onto the plain. Huge amounts of coarse quartz sand were dumped from large scale crevassing and channel shifting. Levees and channels reached heights of 12 to 15 feet above the general level of the plain. On the Korong bahada, at the foot of low granitic hills to the west of Serpentine, more limited sedimentation, overlying the Widgelli calcareous red brown clay(thought to be aeolian) is also regarded as being part of the Mayrung Member. GE OMGRPHOLOGY. Post-Mayrung stream systems flowed lateral to the fan, the present Loddon _River being confined to the east by the fan and to the west by the Korong bahada. Beyond the fan, however, streams form a complex system of anastomosing distributaries over a clay surface. Often the distributaries do not rejoin the main stream and after a short distance divide into a system 'of distributaries. With high discharges from the highlands the terminal distributaries cause sheet flooding on the plain, a substantial reduction in the volume of water passing northward, and ga reduction in the size and number of water courses, so that northwards the distributaries die out as minor scour lines; only the Loddon R., much reduced and confined to a single meandrine channel, reaches Kerang. 'The Loddon R. at Ke rang forms the boundary between the Wimmera and Northern Districts of Victoria. To the east are the alluvial plains of the Loddon R. and Goulburn R. with distinctive fluvial landforms while to the west is the Gredgwin Ridge marking the beginning of the Mallee with its characteristic aeolian landscape. This N-S ridge is the most easterly outcrop of the Diapur Sandstone which forms similar ridges throughout north-western Victoria; it marks the approximate limit of the Tertiary marine transgression in Victoria (Figs. 2, 3). The plain attained its present form in late Quaternary times, having since undergone only slight modification. At that stage sediment in the Ke rang area was largely deposited from a former Goulburn R. system which flowed east from Echuca along the pre sent course of the Gunbower Creek, passing north of the Kow Swamp to Ke rang along the course now followed by the Pyramid Creek, then northwards to Swan Hill, in approximately the same position as that of the Lower Loddon R.
240 Z.`-f -_ Q Am i'<_ g;t .1 -'I 'f 1.;';_i_- A : 1 -_ - i l4f.1. _ :E'.1_._-'.Q ; 'f?_; ;. 1.':' -`; :- :.-,g :; ;.;.:;; _-_L 1; ;.0Z`B1goKE1{ HILL :.- ::. _. nz-_.'.._-.: _ _:E-: it-_: _:.::-0.'. 1.2 ._,Y`}A & _ ::..: 0, -`=: _ --.;» 9* <._'_'.: _-_...:'.,':-.._f_'lv' L..::._-_ 4 GREAT i 15.-` 3f `-I-f*.'._ /5 ARTESIANQ:. _ASIN _, _,fi [fi :-2 S 0 U T a/'f?»2'_fz` _.T :_. :~_ _j._-':_ ' ' ' - A U S T R A -LI It -If-::~f.:3 :Z '::._.= _~,-_-._;.-_-~~:,=4 fa»._ S-.'.'.:':Zf. 1-1 _'_ 'nv ' 1-_'.j_..: _.:...:.».._...::_. :.>, //Z/... '' ' `,.;;_.; :.... :.».:..:'.:.:. ::..1':...»:. /il :_':'. ;';:_I_f j/' ' /`/` r <7 )'3 -_f- 5.'.`: _ 5 5 2_3 3ywiQ I 9*' F&x%»_.] v; Q; _ ~_:' ~,:_ _7 / »_~.:.:. 'lar»., i z.: 1..0 ».::. :g1;.~r~.f_r.1 -,» R* g-.-_-.ra y f 521-Q: _ 'r_`:_i+ Renmark. ws MURRAY # If-:J-:; :1.j / cg»4`$i! $f-i-1'. - -' 4.0:.,;»':. L Xf5f1 // A.... Of 'u' sx E &. I-.D».' _: g:'._ t ;_: j._;_- / 3' _ If MURRI/MBJDGEE }_j ::_ ~612EL}IDEr' I - V ` ` :_ 7-11 :55 fs:-:f ; - :;._-., f * f%;>=. -;.;._.._ -. 3 ' nangatang g //.' '.::, _ -_ ;11 _ =_-j;'»,.; R VER NE Qfolwa /g / 4>Q,.Z,.q1{.a..l.f.».'::»' / 'P /'.'.:.'... -~. '».1-»'...':F /-.':.z':a. '.».a.,» ' pi &.».;»»':'. 3 Z A4 11'-?` / Kerang Z ff -_..,._ }_._,_.._ .. ~-~~.~, _,..'?4g` I»'»f:.?'E Z., E /f._ :..-xxé Zi;. 11_ 4},~'.'. 1:. N,.. f. _-.;_Z ', 5 Z~. I : Z; Nh'll AT-T Z2 221;/Sf' 'Z t_','.' -'X' O I - Tf:~_`,/. _ _Z- [ _' _' ' -1_- '_ -...O Q?.-Q-..2 Ziff :': Pf-, fi i - ' _/1'-,'f,.' `Q j:gi f ' 3 -_g _ : Q. 3-' -' '. [. _ J / 5f_.7_1_'._1 '.'1f 5_3Z-_1_:-I Q 4.KI C T O' -R`. l'a1=:-jg 6 <; f i% 45*`<ti!J' ` ff;.._=;?f?té 5f.~;~ t (_ ;;; <.._:_ _~ _H '. -D-_.:._*_._:._ Q.-._;.,.. *_t.:. .::::.».,_ a_.._ aa»..~....- Bedrock af or close fo otway 0 BASIN _,a a:.s :' > '. -'Z '5 - (1) _.»_...4 ? GIPPSLAND BASIN surface - margin of basins. W _ 2:. -j»j-.;,;.- I au',. _ ~. _ o.._,a 1» : 13)-1- ;;_ ; ;.=LSm n. :a a'a. a at 'OU ' +- 4,. I Approximale exlenf of marine sedimenls in (be Murray Basin 0 iw KILOMETRES zoo I Fig. 2. Extent of the Riverine Plain and Murray Basin ( Lawrence, 1966)
241 .AL/ 2 16 A // < e, v~' _ 3` é;..;,f _ Q? Y~ 1 0 ' f 3 VK > 0 e tfef*.:» `.l..0 _, _. _ :- 4- ;- + -q:e:.;..» e,ee: e..,...,j + _L :.. ;_ / // ' 53 -'41, ' -2- ' 'N f,. f ff f ~ A 1 A.. _?_ + fi* (ff / -_ '? e*f3 1 A - - -ae f`.1, QF -»'`. 7? E r /// T T T T -~ '. '. 2 ' ' ' #. J T. -` ' * '' ='-#rf _ :tk, 4*. _ # '. ~ '.'#..=1= = '# j L/ ~._ 500 1' / / / edycls -ipre-tergery) /-1/4 /f :/;fé~;/,fe,//, / A omrun smosrome mo Loxrou smos w mw~1sool roszmnon EE <:r»»»»m on.na mm. any (Pllocene) Sends and sendslohei. (Miocene) end green, losslllfemus. WUNGHNU GROUP E Nemskav MARL -smack FORMATION (O lgoeene7 to Reeeni) Alluvial cleys, silu, sends. (Oligocene) T Meri. grey, somefimes gleuconiflc. sooxvumouc :sos GEERA Cl-AY a (UPPOY M Ml _ Clay, grey, losiilihreus. (Ollgoeene) ' ' Cllr. blecl. lasslls VINbuooo umssvous.»»»s», grey la Wm., xmcm cnour (Miocene) bbundehl bryozoe. (Eocene to Ollgoeene Cerboneceouaelev. tl' Ind M04- Fig. 3. Diagtammatic section of the Murray Basin (Lawrence, l966) Ek evque acute, E Henan // / W %w/,»7a</ ~ > 7 Q/ZJYAQ? / V V /ff?////ctv/ /////0//,y/_ QQ al /m»/af///4,.,o'f f>,/ga / //f»,.02i ~' // f // ///'7Q7//A///// 1/, / //y / Q' / A<&»~' %4/ ygéa/////z/zz./4//// /5, `Z{_7///A( ev/iff/>z ;~/,/A-;,V, / e M _ /z 0 Q z,///v T, /, /, ';/ I // /,I / /, _»/i,/;/ I f VI, / /, // //I v` / '%;.»4;/ _ /4 /'1 amuse htv&n e' '22 Fzg. 4. Section through east-west dune of the Wootinen Formation, in fhi1w3yc C1U1iI18»»N} (after ChL1rChwa1 d). - Lime-rich zones.
242 The course followed by the former Goulburn R. north of Ke rang was largely dictated by the many pre-existing lunettes randomly distributed east of the Tutchewop lunette on the main lunette ridge. Delayed junctions between more recent stream systems north ofkerang are a reflection of the continued influence of lunettes on the drainage system. Lunettes separate the Loddon R. and Murrabit R. to the south of Benjeroop and the Loddon R. and Murray R. to the north. Lunette s. Between the Loddon River and the Gredgwin Ridge an overlap of fluvial and aeolian landscapes is reflected by the predominance of lunettes. The crescent shaped dunes, often with associated playa lakes, occur flanking the Gredgwin Ridge along a line from Boort to the Murray River. Beyond Ke rang however they are extremely common and coalesce to form an almost continuous ridge, which formed the western limit of Late Quaternary fluvial sedimentation. Aeolian layering in lunettes was first discussed by B.E. Butler (1958); he described the Boort lunette as consisting of Colongulac parna' overlying Widgelli parna, overlying an older parna layer. Laye ring consistently indicates two major phases of lacustrine deflation. In the earlier phase pedogenesis has destroyed the original bedding, and evaporite salts, especially gypsum, lime and halite, initially incorporated in the lunette have undergone distinct remobilization. The more soluble salts have been leached leaving mostly pellet lime and minor gypsum, the latter commonly in vertical pipes. The more recent phase, by contrast, shows little sign of salt movement, and the bedding is often well pre served. Lunettes of the earlier phase occur extensively; the latter phase is less numerous, being largely confined to lunettes around present day permanent or ephemeral lakes e.g. Lakes Tutchewop, Wandella, Boort and Bael Bael. In many the phases are superimposed in a single lunette e.g. Wandella lunette, but elsewhere lateral separation of the different phases results in separate concentric lunettes. ITINERARY LOCALITY L1 - Hope Creek Hope Ck., a tributary of the Loddon R. rises in the granites near Mt. Kooyoora and Mt Korong and flows over granites, Ordovician sediments and Tertiary quartz conglomerates before passing onto the plains. It is the largest of the aggradational systems on the Korong bahada. Sections along the creek showing sedimentary layering in the Korong bahada are typical of others throughout the area although exceptionally clear. Similarities between sequences, despite the differences _in lithologies and extent of the catchments and in the sizeof depositional systems, are believed to strongly support the case for climatic control over layering. The section along the creek shows the Quiamong, Widgelli and Mayrung Members of the Shepparton Formation. The Quiamong Member occurs as flood plain and channel sediments sharply overlain by the calcareous Widgelli Member, which varies from a red brown to a dark grey clay. The Widgelli Member can be traced as a single unit at least Z5 miles to the east, and upstream, almostvto the source of Hope Ck. The Mayrung Member occurs as coarse sands infilling a channel that has been incised throughithe Widgelli Member and into the underlying Quiamong Member. Laminated silts cover both the channel sands and calcareous clays. Downstream the channel changes from a U-shaped gully to a normal V-shaped creek near the Loddon R., and layering is only visible in undercut banks on larger meanders. Between stops and 1 Z, the route crosses part of the alluvial Loddon fan (Mayrung) in which the original prior stream landscape is well preserved. LOCALITY LZ. A disused sand pit, following the course of a prior stream. Coarse sands to sandy clays of the Mayrung Member ove rlie red brown calcareous clays of the Widgelli Member, the latter leached of carbonate near the contact which now occurs as nodules at the level of the sand pit floor. 217
243 218 LOCALITY L3. North of Serpentine the Loddon R. is lateral to the west of the slightly raised Loddon fan. The river, which normally flows along an infilled trough occupied by the Coonambidgal Formation, has left the trough to cut into red brown calcareous clays of the Shepparton Formation. _LOCALITY L4 - Nyah West Quarry. Exposed in the quarry is reddish-brown Diapur Sandstone (Lawrence, 1966) or its synonym, Parilla Sand (Firman, 1966), cemented with limonite. Below 10 to 50 ft. depth (known from drilling) the limonite cement is absent and the formation is a loose sand. Generally the Diapur Sandstone is over 300 ft. thick, a fairly uniform fine to medium grained sand, slightly micaceous, and unfossiliferous. It is thought to be Pliocene. Its upper surface forms prominent topographic ridges which are subparallel and trend NNW-SSE. 0ne of the easternmost, the Cannie ridge, extends northward from Cannie into the Woorinen district. These ridges are thought to represent successive stages of regression, the Diapur Sandstone together with the underlying Bookpurnong Beds representing a well-developed regressive phase of the Murray Basin s youngest major cycle of deposition. LOCALITY L5 - Nyah We st railway cutting. This dune section shows asymmetry typical of E-W dunes of the Woorinen Formation and a complex history (Churchward, pers.comm. ). The sequence from top to bottom at the south is Kyalite Member, Speewa Member, Bymne Member, and Miralie Member at depth(fig. 4). All except the youngest member has a main lime rich horizon, originally part of a B soil horizon. Several additional lime rich zones in the crest of the dune, but not in the more clayey and stable adjacent areas, represent minor phases of instability. LOCALITY L6 - Lake Tutchewop. Lake Tutchewop, towards the northern end of the lunette ridge is an irrigation storage reservoir and permanently full. In its natural state the lake was ephemeral, commonly dry, receiving water only during periods of high flood. A well developed lunette on the east side is strongly gullied and at the N end layers indicate two superimposed phases. Passing southwards along the edge of the lake the phases gradually separate into two distinct lunettes, the younger nearer the lake. LOCALITY LIP.Ke1fQ.gg Re sgeggch Farm. Irrigation has caused both a redistribution of salt and progressive raising of the water# table, with salinization of soils over extensive areas. To combat this drainage systems have been introduced to lower the' water-table below the capillary fringe (ca. 3 to 4 ft.) and more recently pumping from wells. At the Kerang Research Farm one pumping well is tapping a shallow semi-confined sand aquifer thus inducing leakage from the overlying unconfined aquifer and effectively lowering the water-table for an area of more than 50 acres. Hydrogeological investigations are underway seeking areas in the Kerang district which can be dewatered by similar schemes. I1_` Q IfRQ_DUQTIQ_1_ I_. B. ECHUCA-SHEPPARTON AREA 0- (SLM. Bgwler) _ A complex sequence of Late Quaternary fluviatile, lacustrine and aeolian features which have been preserved near Echuca can now be placed in their order of occurrence. Recognition of important neotectonic interruptions in the sequence enables evaluation of the role of other processes e.g. climatic change, on the environment of deposition. In addition, radiocarbon dates for specific events enable comparisons with Quaternary environments of the same age in other parts of Australia. The localities and route for this area are shown on Fig. 1. Fig. l (opposite). The Riverine Plain in the Echuca - Shepparton area. '
244 MATHOURA D )-=~.. FIG. 1 GEOMORPHIC SKETCH MAP OF THE RIVERINE PLAIN NEAR ECHUCA o LI ~I ~I ~IL-~I_~ MILES E.XCURSION ROUTE --+ N t t ROCHESTER ~ G OU~RN ~J'J2' PRIOjR STREAMS ~
245 Z 1 9 ITINERARY LOCALITY 1 - Echuca. Echuca on the Murray R. is 315 ft. above sea level. Before rail reached Echuca in 1864, almost all wool from the area was transported 1,100 miles by river to the coast. After 1864, river transport to and from the rail at Echuca served the Murrumbidgee and northern Riverina areas. Before construction of the Hume Weir upstream in 1936, the Murray at Echuca maintained a mean annual discharge of approximately 5% million acre feet, approximately 1/3 derived from the Goulburn R. joining the Murray 5 miles upstream. During high discharge, the Goulburn contributed much more than 1/3 of the total flow; during the 1956 flood Torrumbarry weir 2.5 miles downstream from Echuca received approximately 12 million acre feet of which the Goulburn contributed 5% million acre feet. The discharge through the Murray upstream at Tocumwal in the same period was 14% million acre feet, most of which flowed north into the Edward system which takes the greater part of Murray effluent waters during high flow. Echuca lies on the southern margin of the Cadell Tilt Block, formed by uplift along the we stern margin of the Cadell Fault (Fig. 1) (Harris, 1938). Leaving Echuca the main road to Deniliquin skirts west of the low area forming the Echuca Depression - the site of a former lake 13 miles across, which formed in the southern part of the fault-angle depression of the Cadell Tilt Block. A low erosion escarpment often only 6 ft. high separates the depression from the higher plain to the west on which the road is built. LOCALITY 2. From 6 miles north of Echuca, the route follows a gravel road north for a further 7 miles across the Cadell Block to the junction of Green Gully and Goulburn Tributary Gully. These abandoned valleys represent the ancient courses of the Murray and Goulburn rivers before drainage was disrupted by the Cadell Fault. They are equivalent to the first Ancestral River phase of Pels (1966). The present channel floors are 14 to 20 ft. below the surrounding plain. Both courses have paired terraces 8 to ll ft. below the plain, with calcareous red brown earth soils, developed on sandy loams which grade down to sands and clayey sands more than 14 ft. thick. They are regarded as tectonic in origin, developed by early tectonic rejuvenation before their final disruption, requiring two separate late Quaternary movements on the Cadell Fault. The upper 10 ft. in the stream channels is light grey plastic clays with carbonate concretions. Channel sands below the clays are more than 30 ft. below the level of the plain we st of the fault indicating relatively deep stream incision compared with that further east. As the road turns east across the meandering channel of Green Gully note the sourcebordering sand dune developed along the northern channel margin. The road from Loc. 2 crosses the Melbourne -- Deniliquin railway line before turning east to rejoin the Echuca - Deniliquin highway. The bitumen road leads south-east towards Echuca and crosses Goulburn Tributary Gully, the floor of which is here 16 ft. below the level of the plain. Note again the sand dunes developed along the northern edge of the stream course on the left side of the road. LCCALIT Y 3. A rough dirt track crosses the course of Goulburn Tributary Gully which can be traced east to the Cadell Fault line. Total displacement determined by the relative levels of the plain on either side of the fault is approximately 40 ft. The downthrown side is clearly delineated by the red gum fore sts on the low-lying swampy areas along the toe of the fault from Barmah to Mathoura. Southwards, the Bama Sand Hills rise to 60 ft. above the plain. They formed along the north-eastern shore of the lake formerly occupying the Echuca Depression (Lake Kanyapella). The route follows a track south through the sand hills to Loc.4. LOCALITY 4.. A sand pit is exposed near the inner edge of the dunes along the road. On their inner or lakeside margin, the Bama Sand Hills form a smooth crescentic ridge outlining in plan the
246 220 position of the former lake shoreline. The regular inner margin of the dune contrasts with the irregular north-easte rn margin along which parabolic dunes have blown out in a north-easterly direction. These dunes have been correlated with a period of aridity (Pels, 1966), assuming they developed from a dry lake floor as postulated by Stephens and Crocker (1946) for the development of normal lunettes. But here, the medium and even coarse sands and gravels in the dune grade out onto the lake floor through fine to very fine sands and silts which persist across the lake to its western margin. This distribution is typical of a coastal foredune developed by deflation off a sandy beach. At Loc.4 is a lake-shore beach with laminations of coarse to fine sands, well sorted within any one lamina. Beds dip at a low angle towards the former lake and contrast with the cross-bedded medium to fine and often poorly-sorted aeolian sands which overlie them. This and other sand lunettes in the area are considered to have formed when the lake was full and are not evidence for aridity. A similar association of lacustrine beach sands with a sand lunette has been observed on the shores of Lake Urana, some 90 miles north-east from Echuca. The route continues south-east from Loc.4 following the toe of the sandhills for 3 miles before turning north and cutting through the dune to Barmah on the Murray River. LCCALIT Y 5. The Murray River flows from Mathoura south-east through the Barmah red gum fore sts, skirting the high sand hills for 5 miles south of Barmah before cutting through them. Following the tectonic defeat of the stream through Green Gully, lakes were formed near' Mathoura and Echuca. The main stream developed around the north of the elevated block to form the Edward River while the Goulburn in the south flowed into the former Lake Kanyapella. The diversion of the Murray south to join the Goulburn is a ve ry recent (Pels, 1964), probably not more than a few hundred years ago. During high discharge, the Edward still collects the greater part of the Murray waters passing through Tocumwal. During floods reverse flow from Barmah upstream towards Mathoura and the Edward River had developed due to high water level near the Goulburn junction downstream. Note the relative absence of recent river deposits along the Murray near Barmah. This and the low sinuosity of the channel reflect the youth of this tract. LOCALITY 6. One mile east of Barmah a sand pit is exposed in the channel of the eastern continuation of the Goulburn Tributary Gully, which can be traced east and south-east to near Shepparton where it is called the Tallygaroopna prior stream. The Broken Creek flows in this channel from east of Nathalia to near Barmah, as a grossly underfit stream. In the pit approximately 18 ft. deep coarse sands and gravels are overlain by finer sands containing limonitically replaced wood fragments. Bedload sands occur only 9 ft. below the surface of the plain compared with a minimum of 30 ft. for stream bed sands in Green Gully and Goulburn Tributary we st of the Cadell Fault (Loc. Z). From Loc. 6, the route returns towards Echuca via Stewart's Bridge, rejoining the south bank of the 'Murray River near where it cuts the Bama Sand Hills. Approximately mile south, 1 a large abandoned channel (now a lagoon) on Madowla Park marks the former entry of the Goulburn R. into the ancient Lake Kanyapella. The channel passes we st into a distributary system, this having the only coarse sands and gravels found in sediments of the for- ` mer lake. Finer sands were removed by wave action from this gravel fan and spread along beaches on the north-easte rn shore of the lake to be finally blown into the sandy foredune or lune tte. LOCALITY 7. One and a half miles within the lake strandline is the southern bank of the Murray R. which has ll ft. of bleached lacustrine silts with charcoal and organic remains overlying dark grey prismatic structured clays with cutans and extensive manganese staining. The lower horizon represents a buried soil developed on a surface which existed before drainage was disrupted by movements on the Cadell Fault. The higher lacustrine silts represent the first deposition after movement on the fault. A radiocarbon date of 6, 800 ;t 150 BP was obtained from charcoal fragments 4 to 5 ft. above the buried soil. Allowing for the deposition
247 ZZ1 of this lower 4 to 5 ft. of sediments, the age of the final movementson the fault is estimated at between 8, 000 and 10, 000 BP. The preservation of fine laminations in the lacustrine silts throughout the Echuca Depression indicates the absence of plants and burrowing organisms in the lake. Laminae probably result from storm waves distributing silts in suspension from the eastern margin. The low percentage of clay in the lake sediments indicates its progressive removal from the system, probably through an overflow outlet to the west. The present mean annual discharge of the Goulburn River is approximately 2,400, 000 acre feet. This compares with the total evaporation loss from a lake of this size (using an evaporation rate of 58.4 in. per year) of approximately 400, O00 acre feet. Thus the present Goulburn could sustain a lake approximately 6 times _the area of Lake Kanyapella. The low percentage of clays, as 'well as the absence of any saline accumulation in the lake sediments is consistent with their progressive removal from the lake through effluent drainage. The absence of a well developed strandline sequence, reflecting little variation in water level, requires the overflow level to have remained constant throughout the period of beach and foredune construction on the north-easte rn shore. The only inner strandline feature is a small lunette Z ft. high, adjusted to a strandline 10 ft. below that required to build the Bama Sand Hills. From Loc. 7, the road travels across the lacustrine sediments through a low lying area subject to flooding, towards the Goulburn-Murray junction. LOCALITY 8. A 2.-3ft. drop in level and small channels are seen. This undulating topography with ridges only 1 to Z ft. above the intervening depressions, lies a few feet below the level of the plain and represents point-bar traces deposited by channels which incised some 30 ft. into the lake floor. The point-bars are arcuate and sub-parallel maintaining a long meander wave-length compared to present streams in the area. One mile south of the road, source-borde ring sand dunes have been formed in association with the point-bars. Sand has blown from the channels or sandy point-bars onto the former lake floor. The river system here can be traced back along the present Goulburn whose course it mainly controls. It maintains the characteristic long wave-length, large radius of curvature and wide meander belt in sharp contrast to the channel morphology of the present Goulburn. A stream with these characteristics would seem to require a much higher bankfull discharge than that of the present Goulburn. The formula of Dury (1965) applied to meanders of this system gives a bankfull discharge of approximately 50,000 cusecs compared with a present bankfull discharge of the Goulburn at Shepparton, 9, 000 cusecs. The system corresponds to the Ancestral River Z system of Pe1s(l966). LOCALITY 9. Half a mile south-west of the bridge, the Goulburn River has exposed sediments of a small leveed stream with a channel floor in places 6 to 8 ft. above the level of the plain. This and another similar stream on the lake floor have been named the Kanyapella prior streams (Bowler 8: Harford, 1966). At Loc.9, a shallow channel has been cut into the lake sediments and backfilled with sands. Some 60 yards west of the channel micaceous levee sands ove rlie laminated organically rich lacustrine silts, re sting on a buried soil similar to that seen at Loc. 7. The sequence downwards is :- O _- 9 ft. LEVEE SEDIMENTS - micaceous silts coarsening in depth to micaceous fine quartz sands ft. LACUSTRINE SEDIMENTS - bleached laminated silts with leaf remains grading down to medium to coarse sands ft. BURIED SGIL - dark grey clays with prismatic structure and manganese staining on ped faces, with increasing sand at depth. Abundant carbonate conc retions occur near the prior stream` channel and levee sediments with which they originated, as elsewhere throughout the Rive rine Plain. Charcoal from the
248 prior stream sands at this site has beendated as 4200 (+ 130) BP. These prior streams are younger than the sediments of Lake Kanyapella and cros-sed the lake floor after the lake had finally disappeared_ by either draining or evaporation. They entered it at the same point as the present Goulburn but their channels and fine bedload indicate a much smaller flow. The route follows the gravel road for 4 miles east across the lake sediments with the Goulburn River on the left, until it turns north to the river and Loc. 10. LOCALIT Y 10. On the track to the river, 3 surfaces crossed at different elevations represent different depositional phases in the late Quaternary sequence. The first is the level surface of the lake floor. Half a mile south of the Goulburn River this gives way to an undulating topography ave raging 2 to 3 ft. below the lakefloor and representing a point-bar system of ancestral river Z., similar to that at Loc. 8. Near the Goulburn River, a sharp topographic break separates the A.R. Z surface from an undulating alluvial surface 6 ft. lower containing the present river channel. This represents the ancestral river 3 system of Pels (1966) to explain which he has postulated an arid-pluvial cycle after a period of high discharge in A., R, 2 time. However these features are here regarded as part of the pre sent Goulburn system. There is no evidence of aridity between the A.R. 2 system and that of the present river regime. The differences between the two systems can be accounted for by a single decrease from high discharge in A.R. Z time (with high discharge, frequent flooding and point-bar building to the level of the present A.R. 2. surface) to a period of lower discharge, lower flood height and lower depositional levels corresponding to the present regime. From the difference in elevation of the stream bed, differences in channel morphology and sediment characteristics, the A.R. 2 channels are regarded as a separate depositional phase and younger than the Kanyapella prior streams i.e. less than 4,000 years BP. The route continues east and south-east along the gravel road crossing the elevated channels and levees of the Kanyapella prior streams. LOCALITY l l. A small lake (Little Kanyapella) developed late in the sequence within the confines of the larger strandline. It cut the high levees of the southernmost Kanyapella prior stream, and built a sand lunette 5 miles long across them on the north-eastern margin. As at the Bama Sand Hills, this lunette formed while the lake was full, supplied from the Goulburn system through Yambuna Creek. It formed in the high discharge period of A.R. Z. The lakeeventually ove rtopped and cut a channel back to the Goulburn River. The route follows the gravel road back towards Echuca rec rossing the prior_stream channel near where it is overlain by the sand lunette to meet the Murray River near Loc. 12. LOCALITNY 12. In a stratigraphic section exposed on the south bank of the Murray R., laminated lacustrine silts overlie a buried soil similar to that seen at Loc. 7, 9 and 10. The lake sediments here have thinned to only 5 ft. thick compared with 11 to 13 ft. at Loc. 7 to the east. LOCALITY 1 3. Here a low topographic escarpment divides the plain on the east of ave rage elevation 32.0 ft. from a 10 ft..higher plain on the west. A prior stream course with recognisable channel-levee form crosses the road. Levels along the stream bed rise at 1 in 60 across the escarpment, then fall to the north-west at a low gradient of in The stream bed has therefore been 1 warped during the formation of the escarpment indicating its tectonic origin and explaining the elevation of the we ste rn block. The escarpment continues for 5 miles to the south before swinging to the south-we st and dying out near Rochester (Fig. 1). Post-tectonic alluvial deposition has been limited to the downthrown side. Soils developed on the surficial layers consist of calcareous clays and clay loams, often with gilgai micro-relief, in contrast to the loams and sandy loams soils developed on the levees of younger prior streams to the east and south-east. Near Loc. 13, clays (usually calcareous) ove rlie both channel and levees of the deformed prior stream. A profile at this locality consists of :-
249 in. red brown clay loam, with sharp contact to 4 - Z0 in. heavy red clay, good crumb, with moderately developed clay skins to 15, gypsum at 15 to 20 in. 1 Z0-48 in. grey clay loam with red mottles, pedality increases below gypseous layer at 2.0 in., clay skins better developed, red clay often forms coatings on ped faces. This grades into in. pale grey sandy clay loam to sandy loam, red clay stains on ped faces, black Mn stains and some wormcasts. Becomes coarser and micaceous in depth and contains occasional Mn nodules in the lower 40 in. A possible sedimentary break occurs near Z0 in., separating lower micaceous alluvial sediments with soil structure, from upper gypseous (and usually calcareous) clays which persist as a mantle across the upper block. The upper clay in this levee is' difficult to explain as alluvial and may be aeolian as postulated by Butler (1961) for other areas on the Riverine Plain. From Loc. 13, return north and continue east along the Murray Valley Highway. For the next 6 miles the highway follows the southern edges of the Echuca Depression crossing a series of prior stream courses which originated in the Goulburn catchment to the southeast. The escarpment corresponding to the southern shoreli.ne of Lake Kanyapella is eroded into the prior stream sediments and is therefore younger than them. McCoy s Bridge across the'goulburn River is one of the few localities where the Goulburn has cut away from the point-bars of Ancestral River Z deposits which occur % mile further north. The river broke away from these depressions 3 miles upstream from McCoy's Bridge and flows in a low belt of undulating and recently deposited alluvial silts and sandy clays. Note the different meander pattern of the river here compared with its upstream continuation towards Shepparton where it is controlled by the ancient point-bars of A.R. Z. The bed of the river at McCoy's bridge is cut in older lateritized alluvial sediments. No channel aggradation has occurred here since the diversion away from the A.R. Z system. The route continues north into the undulating topography of A. R. 2 point-bars. LOCALIT Y 14. A large gravel pit has been cut into deposits of the ancestral river. The clean coarse bedload and abundance of associated source-bordering sands, indicate these were bedload streams in the sense of Schumm (1963), and would require relatively high transporting velocities compared with the Kanyapella prior streams seen at Loc. 9 in the Echuca Depression. Channel sands and gravels are overlain by clayey sands and clay loams on which a weakly differentiated grey podsolic soil profile has developed. Sand dunes associated with the point-bars in this system are the youngest dunes in the area. They occur further upstream near the present Goulburn as far as Tabilk where, on account of their free drainage qualities, they are used for Viticulture. One mile north of here, the course of Wakiti Creek, an underfit stream is controlled by the meandering undulations of A.R. Z point-bars. The route crosses Wakiti Creek following the north sideofthe Goulburn River. Sand dunes of the A. R. Z system form rises along the river margin to the south. LOCALIT Y 15. Approximately 14 miles south-east of the turn-off to Shepparton, the road meets the levees and sand hills of the Tallygaroopna prior stream. This is the upstream continuation of the Goulburn Tributary Gully (equivalent to A.R. 1 of Pels) seen on the Cadell Block at Loc Z and 3. However he re it has all the features of an aggraded prior stream lacking the main defined characteristics of an ancestral river. Upstream, the courses of A.R. Z and the Goulburn R. are largely controlled by the Tallygaroopna prior stream. LOCALIT Y 16. At the site of a line of bores sunk at Koyuga are cores and sludge samples. This line of bores, along with others at Kyabram and Toolamba drilled across a prior Goulburn distributary, show the deposits slope to the north-we st at an average gradient of and
250 224 that the depth to the base of these deposits, where laterally accreted, varies from ZZ to 35 ft. at Toolamba, 20 to Z9 ft. at Kyabram, and Z1 to Z7 ft. at Koyuga. These laterally accreted deposits usually fine upward from coarse-grained sand at the base through silt, clayey silt, a sandy clay, with the uppermost part of the profile represented by clays which are usually silty. They belong to the Quiamong Member of the Shepparton Formation. LOCALITIES 17, 18. At two sections - at Kialla and Arcadia - on the banks of the Goulburn River the river has cut out of its associated deposits of the Coonambidgal Formation into older sediments of the Shepparton Formation. The Shepparton Formation at Kialla can be subdivided on the basis of paleosols into several members. From top to bottom the sequence is 0-5 ft. pale brown to brown Clays of the aeolian Widgelli Member and the alluvial Quiamong Member ft. light grey to yellowish brown silts of the Katandra Member. 18+ ft. very fine to medium grained sands, clayey, displaying yellowish red to light grey mottles of the Kialla Member. Within this unit are lenses and beds of more sandy material which are partially cemented with iron sides to give sandstone. The Kialla Member continues below water level. At Arcadia the exposed section is similar to that at Kialla but disconformities and the upward fining of members are better displayed. REFERENCES Bowler, J.M. and L. B. Harford, Quaternary tectonics and the evolution of the Riverine Plain near Echuca, Victoria. J. Geol. Soc. Aust., 13, Butler, B.E_, Depos'itiona1.systems of the Riverine Plain of south-eastern Australia in relation to soils. Soil Publ. C. S.gI,R. O, Aust., 10. Butler, B.E., Ground surfaces and the history of the Riverine Plain. Aust. J`.Sci. 24, 39 40o Dury, G.S., Theoretical implications of underfit streams. U.S. Geol. Surv. Prof. Paper 452-C, 43 p. Harris, W.J The physiography of the Echuca district. Proc. Roy. Soc. Vic., 51, Johns, M.W., and Lawrence, C.R., Underground water resources of the Northern Plains of Victoria. Dept. Mines. Vic., Underground Water Inv. Rep.1. Lawrence, C.R., Cainozoic stratigraphy and structure of the Mallee Region, Victoria. Proc.Roy.Soc.Vic., 79, Pels, S., The present and ancestral Murray River system. Aust.Geog.Studies, 2, Pels, S., Late Quaternary chronology of the Riverine Plain of southeastern Australia..]_. Geol. Soc. Aust., 13, Schumm, S.A , A tentative classification of alluvial river channels _Q_.S_.Geo_l._S_u r_v y_ Circular 477, 10 p. Stephens, C.G., and Crocker, R.L., Composition and genesis of lunettes. Trans.Roy. Soc.S. A_u_s_1, 70,
251
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