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Geological Society of Australia

ABSTRACTS Number 80

Victorian Universities Earth and Environmental Sciences Conference 19 September 2005 The University of Melbourne

VUEESC Victorian Universities Earth and Environmental Sciences Conference 19 September 2005

Program & Abstracts

Hosted by: School of Earth Sciences The University of IVIelbourne

Editors:

Adrian F. Corvino Kim S. Ely

Geological Society of Australia Abstract Volume Number 80

Geological Society of Australia Abstracts Number 80 Victorian Universities Earth and Environmental Sciences Conference September 2005

Editors: Adrian F. Corvino and Kim. S. Ely

ISSN 0729 011X © Geological Society of Australia Incorporated, 2005

Recommended citations: Corvino, A. F. and Ely, K. S. (eds) 2005. Victorian Universities Earth and Environmental Sciences Conference. Geological Society of Australia Abstracts Number 80, p. 48. Mitchell, J. K., Holdgate, G. R., Wallace, M. W. and Gallagher, S. J. 2005. Marine geology of the Pliocene to recent Bass Canyon, SE Australia. In: Corvino, A. F. and Ely, K. S. (eds) Victorian Universities Earth and Environmental Sciences Conference. Geological Society of Australia Abstracts Number 80, 15.

Copies of this publication may be obtained from: The Business Manager Geological Society of Australia Incorporated Suite 706 Thakral House, 301 George Street Sydney NSW 2000 Australia

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

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Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Predictive Mineral Discovery Cooperative Research Centre

pmd^CRC Minerals Council of Australia Minerals Tertiary Education Council

Australian Government "''

Australia Bureau of Meteorology

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Postgraduate Association Inc.

Organising committee Angela Bush Convenor

Vaughan Barras Multimedia

Adrian Corvino Executive editor

Johann Diener

Kim Ely

Louise Edwards

Proceedings

Assistant editor, Program & proceedings

Program & proceedings

Jonathan Giddings Sponsorship

Kate Harper Catering, Program & proceedings

Fabian Kohlmann Proceedings

Jeremy Mitchell Printing, Program & proceedings

Christian Seller Proceedings

Estee Woon Sponsorship

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Program Fritz Loewe Theatre 9.00 9.10

Welconne and opening remarks Jim Bowler: The Role of Climate Change in the Study of Earth Sciences

9.45

Theme 1: Climatology Meneghini et a!.: Australian rainfall: its link with the Southern Annular Mode

10.00 10.15 10.30 10.50 11.05 11.20

Chandler: Potential changes in hail frequency and severity in a future climate Reid: Characteristics of intense extratropical cyclones in the southern ocean Coffee break Theme 2: Tectonics Ervin: Neotectonic and landscape evolution of Atauro Island, Timor-Leste Harper: Geomorphic evidence of late stage convergence-parallel extension in an arc-continent collision zone, East Timor Phillips et al.: Evidence of Neoproterozoic rifting within the Southern Prince Charles Mountains, East Antarctica: a detrital zircon study Theme 3: Sedimentology and Palaeoecology

11.40

Martin: Trace fossils on echinoid skeletons from the Oligocene-Miocene Abrakurrie Limestone, Eucia Basin, Western Australia

11.55 12.10

Consoli & Stillwell: The Chatham Island's Takatika Grit, Cretaceous-Tertiary (K-T) boundary succession Coffey et a!.: The palaeontology and environments of the Plio-Pleistocene white smokers of the Cape Vani Mn deposit on Milos, Greece

12.25

Mitchell et al.: Marine geology of the Pliocene to Recent Bass Canyon, SE Australia

12.40

Lunch break and poster session

13.40

Mike Sandiford: Futures in Earth Sciences Theme 4: Economic and Mine Geology Thorp et al.: Three dimensional modelling of gold mineralisation in the Woods Point District, Victoria McLellan et a!.: Constraining the geology of Broken Hill, NSW, Australia, in three dimensions using geophysical methods and inversion techniques

14.15 14.30 14.45 15.00 15.15

O'Sulllvan: Amphibolites of the Eastern Succession, Broken Hill, New South Wales Hassell: The geochemical and hydrogeological characteristics of an abandoned tailings dam at Savage River Mine, Tasmania Coffee break Theme 5: Vertebrate Palaeontology

15.35

Fitzgerald: Diversity and novelty in the early evolution of Baleen Whales (Mammalia: Cetacea: Mysticeti)

15.50

Shean & Hellstrom: A comparative anatomy of Palorchestes Azael (Marsupialia: Diprotodontoidea: Palorchestidae) from the Buchan Caves region. Northeast Victoria

16.05

Buchanan: New fossil crocodile material from the Eocene Kerosene Creek Member, Rundle Formation, Queensland

16.20

Piper: Preliminary taphonomic and palaeoenvironmental interpretations of the Early Pleistocene Nelson Bay local fauna, Portland, Victoria Theme 6: Geochemistry and Geodynamics

16.40

Miller & Kennett: Spatial and temporal evolution of the subducting Pacific Plate beneath Northeast Asia: evidence from tomography and paleogeographic reconstructions

16.55 17.10 17.25 17.40

Heyworth et al.: Insights into magma generation and evolution at White Island, New Zealand Mason et al.: A 3D dynamic model of the Izu-Bonin-Mariana subuction zone Hawke: Geodynamic evolution, stratigraphy and geochemistry of Atauro Island, East Timor Awards and closing remarks

111

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Contents Theme 1: Climatology Australian Rainfall: Its Link with the Southern Annular Mode B. MENEGHINI,

I. Simmonds

and I. N. Smith

Potential Changes in Hail Frequency and Severity in a Future Climate E. B. CHANDLER

Characteristics of Intense Extratropical Cyclones in the Southern Ocean L REID

The Effect of Global Warming on High-Chill Fruit Vernalisation R. O. DARBYSHIRE

Theme 2: Tectonics Neotectonic and Landscape Evolution of Atauro Island, Timor-Leste D. B. ERVIN

Geomorphic Evidence of Late Stage Convergence-Parallel Extension in an Arc-Continent Collision Zone, East Timor K. HARPER

Evidence of Neoproterozoic Rifting within the Southern Prince Charles Mountains, East Antarctica: A Detrital Zircon Study G. PHILLIPS,

C. J. L Wilson, I. H. Campbell

and C. M. Allen

Geology of the Clemence Massif, Central Prince Charles Mountains, East Antarctica A F. CORVINO

and C. J. L Wilson

Theme 3: Sedimentology and Palaeoecology Trace Fossils on Echinoid Skeletons from the Oligocene-Miocene Abrakurrie Limestone, Eucia Basin, Western Australia S. K. MARTIN

The Chatham Island's Takatika Grit, Cretaceous-Tertiary (K-T) Boundary Succession C. P. CONSOLIandJ.

D. Stillwell

The Palaeontology and Environments of the Plio-Pleistocene White Smokers of the Cape Vani Mn Deposit on Milos, Greece J. M. COFFEY,

S. J. Gallagher,

I. R. Plimer and T. Rich

Marine Geology of the Pliocene to Recent Bass Canyon, SE Australia J. K. MITCHELL,

G. R. Holdgate,

M. W. Wallace

and S. J. Gallagher

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Insects of the Early Jurassic Cattamarra Coal Measures, Western Australia: Pinpointing the Origins of a Modern Fauna S. K. MARTIN

Modern Seafloor Environments (Sedimentary, Foraminiferal & Ostracode) of the Pitt Water Estuary, South-East Tasmania D. C. LEWIS

Palynological Evidence of Vegetational Change in Early Cretaceous Sediments, Gippsland Basin, Victoria D. E. SEEGETS-VILLIERS

Theme 4: Economic and Mine Geology Three Dimensional Modelling of Gold Mineralisation in the Woods Point District, Victoria N. P. THORP, L Ailleres

and F. Bierlein

Constraining the Geology of Broken Hill, NSW, Australia, in Three Dimensions Using Geophysical Methods and Inversion Techniques A MCLELLAN,

L Ailleres

and R. Weinberg

Amphibolites of the Eastern Succession, Broken Hill, New South Wales R E. O'SULLIVAN

The Geochemical and Hydrogeological Characteristics of an Abandoned Tailings Dam at Savage River Mine, Tasmania T. HASSELL,

J. Webb and D. Ray

Investigating the Thermal State of the Crust, a Model from Western Victoria D. V. WIJERATNEand

G. R. Beardsmore

Mineral Exploration Under Cover: 3D Modelling of Gold Mineralisation, Walhalla, Victoria M. HOUGH,

L Ailleres,

F. P. Bierlein,

C. Willman, A. Seymon and S. Hutchin

Direct Dating of Ore Minerals: a Feasibility Study of the Pb-Pb Isotope Step-Leaching Technique K. BASSANO,

J. Hergt, R. Maas and J. Woodhead

Theme 5: Vertebrate Palaeontology Diversity and Novelty in the Early Evolution of Baleen Whales (Mammalia: Cetacea: Mysticeti) E. M. G. FITZGERALD

A Comparative Anatomy of Palorchestes Azael (Marsupialia: Diprotodontoidea: Palorchestidae) from the Buchan Caves Region, Northeast Victoria D. A SHEAN and J. Hellstrom

New Fossil Crocodile Material from the Eocene Kerosene Creek Member, Rundle Formation, Queensland L A BUCHANAN

Preliminary Taphonomic and Palaeoenvironmental Interpretations of the Early Pleistocene Nelson Bay Local Fauna, Portland, Victoria K. J. PIPER

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

A Heterocercal Caudal Fin from Dinosaur Cove, Otway Group, Victoria (Early Cretaceous: Aptian Albian), Identified as Psilichthys cf Selwyni Hall, 1900 (Actinopterygii: Palaeonisciformes) M. P. INGLIS

A Review of the Pleistocene Vertebrate Faunal Assemblage at Buchan, Victoria D. A. SHEAN

A Review of Current Australian Fossil Crocodiles and Mekosuchinae in Literature L A BUCHANAN

Chatham Islands Theropods: Dinosaur Sanctuary from K-T Boundary Succesion C. P. CONSOLi J. D. Stilwell, R. Sutherland, S. Salisbury, T. H. Rich, P. A. Vickers-Rich, P. J. Currie and G. J, Wilson

Theme 6: Geochemistry and Geodynamics Spatial and Temporal Evolution of the Subducting Pacific Plate Beneath Northeast Asia: Evidence from Tomography and Paleogeographic Reconstructions M. S. MILLER and B. L. N. Kennett

Insights into Magma Generation and Evolution at White Island, New Zealand Z HEYWORTH, R. M. George, B. F. Schaeferand S. P. Turner

A 3D Dynamic Model of the Izu-Bonin-Mariana Subuction Zone W. G. MASON, D. Stegman, L Moresi and P. G. Betts

Geodynamic Evolution, Stratigraphy and Geochemistry of Atauro Island, East Timor M. L. HAWKE

Intraplate Hypersthene-Bearing Trachyandesites: Evidence for Muliple Magma Sources in the Newer Volcanics Province, Australia Z. HEYWORTH, B. F. Schaefer and I. A. Nicholls

Definition and Classification of the St Peter Suite Stratigraghy, Western Gawler Craton N 0. CHALMERS AND B. F SCHAEFER

Prediction of Sludge Composition and Water Quality from Lime Neutralisation of Acid Rock Drainage D. M. MCDONALD and J. A. Webb

Theme 7: Hydrogeology Groundwater Flow in a Tertiary-Quaternary Alluvial Sequence in the Mount William Creek Valley, Western Victoria, and the Potential for Upward Leakage to Induce Dryland Salinity M. D. EDWARDS and J. A. Webb

Geology and Hydrogeology of a Tertiary Deep Lead Palaeodrainage System in the Gleneig Hopkins Catchment, Western Victoria M. RAIBER and J. A. Webb

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 1

Climatology

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

AUSTRALIAN RAINFALL: ITS LINK WITH THE SOUTHERN ANNULAR MODE B. MENEGHINl\ 1. Simmonds^ and I. N. Smith^ ^ School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia ^CSIRO Atmospheric Research, Aspendale, Victoria, Australia Recent investigations into the cause of the decline in southwest Western Australian winter rainfall have found that the strong positive trend in the Southern Annular Mode (SAM) may be responsible. One way the SAM can affect rainfall is through its influence on the position of the polar front jet, which in turn affects extratropical cyclones and cold fronts. Given this, the recent decreases in winter rainfall in Victoria and Tasmania may also be related to variability in the SAM. Here we explore the relationships between the SAM and seasonal Australian rainfall. Since El Nino Southern Oscillation (ENSO) is known to have a significant influence on Australian rainfall, these relationships are compared to that between ENSO and Australian rainfall. We

construct a SAM index using the ERA40 mean sea level pressure reanalysis for September 1957 to August 2002, and correlate this with Bureau of Meteorology grid point rainfall. For 1958-2002 significant inverse relationships between rainfall and the SAM are found in southern Australia (southwest Western Australia, southern South Australia, Victoria and Tasmania), while significant inphase relationships between rainfall and the SAM are generally found in the northern half of Australia (northern Western Australia, Northern Territory, Queensland and northern New South Wales). These results suggest that the SAM may be partly responsible for the decrease in winter rainfall in Victoria and Tasmania as well.

Keywords: Australian rainfall, Southern Annular Mode, Southern Hemisphere circulation

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, Septennber 2005

POTENTIAL CHANGES IN HAIL FREQUENCY AND SEVERITY IN A FUTURE CLIMATE E. B. CHANDLER School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia Hail is precipitation in the form of balls of ice which are produced by convective clouds, mainly associated with the more severe thunderstorms that occur on the planet. Thus the temporal and spatial variability of hail is its prime characteristic, with a variability exceeding that of most other weather conditions. As the future climate is expected to change under global warming conditions, there is considerable interest in the future state of extreme weather conditions such as that of hail and thus an understanding of the past trends of hail events in different areas Keywords: hail, climate change, total-totals index E-mail: e.chandler@ugrad.unimelb.edu.au

may help us to understand the likely future changes this phenomenon will undergo in the future. This project uses NCEP2 reanalysis data from 1979-2004 in addition to hail reports from the Bureau of Meteorology over this time frame to examine any past changes in hail events in the Southeast Queensland region of Australia. The main indices used in this analysis was the total-totals index which is a simple measure of atmospheric instability and can be used as a prediction of severe storms.

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

CHARACTERISTICS OF INTENSE EXTRATROPICAL CYCLONES IN THE SOUTHERN OCEAN L REID School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

The Southern Ocean has within it some of the strongest extratropical cyclones found anywhere in the world. Over the last fifteen years many climatologies of Southern Hemisphere extratropical cyclones have been performed, with particular interest in the growth, movement and decay of the cyclones. Many of the studies that have been performed have noted the intensity of the cyclones only in passing, and only use their own parameters to define what the intensity is without much thought to how it has been done in the past. As the threat of climate change continues, many models have forecast that there will be a decrease in the number of cyclones, but there is very likely to be an increase in the intensity of those cyclones. If this is to be the case then it is necessary to create a

comprehensive definition of what an intense cyclone is, based upon several parameters. Then, with those findings assess whether cyclones are in fact increasing in intensity as has been proposed. Thus in this research the ECMWF, ERA-40 data shall be used in conjunction with the Melbourne University cyclone tracking scheme to try and determine the characteristics needed to define an intense extratropical cyclone. Then find where and when they occur most commonly during the year and finally to asses how the cyclones have changed during the ERA-40 period. Thus far the intense cyclones tend to occur in the southern Indian Ocean, where they have the potential to affect southern Western Australia.

Keywords: extratropical cyclone. Southern Hemisphere, Southern Ocean, intensity, strength

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, Septennber 2005

THE EFFECT OF GLOBAL WARMING ON HIGH-CHILL FRUIT VERNALISATION R. O. DARBYSHIRE School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

Future temperature rises as a result of increased greenhouse gas emissions have been predicted across much of Australia. Such changes to the climate may influence the productivity of high-chill pome and stone fruit by reducing the amount of winter chilling received. The accumulation of chilling temperatures is commonly measured in Chill Units (CU) according to accumulation based on the Utah Model. Each variety of fruit requires a different amount of accumulated CU to avoid damage due to insufficient chilling. Additionally, the optimum temperature that chilling occurs also varies with cultivars. The Utah Model and a second, lesser known model for CU accumulation, the Dynamic Model, are used in this study. Both these models require hourly temperature data as input. However, it is standard to interpolate

the diurnal cycle using daily maximum and minimum temperatures producing hourly data. This paper investigates any bias that may be associated with using lower temporal resolution data than the models require. Past trends in CU accumulation at sites of horticulture are also considered, with the output of both the Utah and Dynamic Models regarded. Further analyses of trends using the Utah Model are also presented, which were run with various threshold limits, specific to different fruit species. Warming scenarios for 2030 and 2070 have been recently issued by the CSIRO. Future projections, using these scenarios for both the previously mentioned models are simulated. High and low regional warming outcomes are used to estimate the likely impact of an increase in temperature on CU accumulation and hence fruit productivity.

Keywords: global warming, Chill Unit, Utah Model, Dynamic Model E-mail: r.darbyshire@ugrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 2

Tectonics

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

NEOTECTONIC AND LANDSCAPE EVOLUTION OF ATAURO ISLAND, TIMOR-LESTE D. B. ERVIN School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

The volcanic island of Atauro is part of the inner Banda Arc situated 670 km northwest of the Australian continent. The genesis and evolution of the Banda Arc is associated with complex deformation history. Australian continental shelf sediments jammed the subduction zone in the Late Neogene, instigating oblique arc-continent collision of the Indo-Australian and Eurasian plates in the Banda region. Understanding the neotectonic and landscape evolution of Atauro is crucial in unravelling the history of the Banda Arc. The initial magmatic topography of Atauro erupted violently in a sub-aqueous environment between 3 and 3.5 Ma. Temporal and spatial changes in Quaternary climate, regional geodynamics and surface processes have given shape and form to the present landscape of Atauro Island. The landscape evolution of Atauro may help constrain geodynamic evolution of this portion of the Banda Arc and yield insights into the couplings between tectonic and climatic forces.

Field work focused on creating the first geological map of Atauro. Using structural, stratigraphic and geomorphic interpretations, a series of palaeogeographic surface models of Atauro were constructed. The palaeogeographic surfaces of Atauro were then used to produce initial topologies in numerical landscape simulations. Landscape experiments were designed and implemented to investigate the interactions between Quaternary climate oscillation, tectonic uplift and landform evolution. Landscape modeling was conducted on the Surface Process Model (SP-Model), a model is that run on cluster (multi-processors) computers facilitating finer resolution landscape models. Geological observations suggest a major volcanic centre has collapsed off the northeast coast of Atauro. This unloading is expected to produce structural and isostatic responses in the landscape. Numerical modeling allows us to explore a spectrum of possible landscape responses.

Keywords: neotectonic, geodynamics, landscape evolution, modeling E-mail: dbervin@ugrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environnnental Sciences Conference The University of Melbourne, September 2005

GEOMORPHIC EVIDENCE OF LATE STAGE CONVERGENCEPARALLEL EXTENSION IN AN ARC-CONTINENT COLLISION ZONE, EAST TIMOR K. HARPER School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia Collision of the northward migrating Australian continent with the Eurasian plate occurred during the Neogene causing the rapid uplift and exhumation of Timor. The incorporation of buoyant continental lithosphere into the subduction zone has led to a Late PlioPleistocene reorganisation of the plate boundary in the Timor region, with the consequence that Timor is now deforming in a vastly different manner compared to earlier stages of collision. One important indication of this change is its relative aseismicity. This research is aimed at understanding the landscape response to collision and the subduction zone processes that must accompany early stages of collision such as slab tearing, by focusing on a convergenceparallel extensional fault producing --1000 m uplift in central Timor. The region discussed in this talk is located in central Timor, where it is plausible that collision is at its most advanced stage, due to the fact that here: 1) the topographic relief is

the greatest on the island; 2) the width of the accretionary prism is the widest; and 3) the distance to the inner-arc is at its smallest (only 30 km). The orogen-parallel Cablac mountain range separates the mountainous region to the north from the southern coastal plains. The kilometre scale uplift of Mount Cablac has been generated from the footwall uplift of a north dipping, oblique dextral normal fault. Drainage rearrangement in the footwall basin revealed by a remarkable record of fluvial terraces demonstrates continued uplift into the Late Pleistocene-Recent. The existence of convergence-parallel extension in a region of former convergence is consistent with a significant reorganisation of the lithospheric stress field. It is hypothesised that this reflects regional scale uplift associated with mantle processes such as slab tearing and is supported by the postconvergence Late-Pliocene to Pleistocene sedimentary record that demonstrates over 2 kilometres of uplift.

Keywords: arc-continent collision. East Timor, extension, landscape evolution, uplift E-mail: k.harper@pgrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

EVIDENCE OF NEOPROTEROZOIC RIFTING WITHIN THE SOUTHERN PRINCE CHARLES MOUNTAINS, EAST ANTARCTICA: A DETRITAL ZIRCON STUDY G. PHILLIPS\ C. J. L W i l s o n \ I. H. Campbell^ and C. M. Allen^ ^ School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia ^ Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

sediments of the younger Lambert Province display different provenance signatures to the Ruker Province. This indicates that either a tectonic contact exists between the two or the Lambert Province resembles a higher stratigraphic level that received detritus from a different source terrane. Overlying the Ruker and Lambert provinces is the Sodruzhestvo series, an expansive cover sequence of mature, clastic sediment that was deposited during the Neoproterozoic (ca. 950 - 650 Ma). The rift or basin related deposition of the Sodruzhestvo series indicates that significant periods of extension affected the southern PCM during the mid to late Neoproterozoic. An extensional tectonic regime within the East Antarctic Shield during the mid- to- late Neoproterozoic could possibly be attributed to the break-up of the super-continent Rodinia.

Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICPMS) of detrital zircon from low-grade sedimentary cover sequences within the southern Prince Charles Mountains (PCM) has addressed: (1) the stratigraphic architecture and associated windows of deposition; (2) source terranes the sediment was derived, and thus juxtaposed crustal fragments and; (3) tectonic models attributed to the evolution of the region and thus greater East Antarctic Shield. Three prominent Archaean-Mesoproterozoic basement cover sequences characterise the Ruker Province that comprises the lower stratigraphy of the southern PCM. Detritus was more than likely sourced from the underlying felsic crystalline basement, indicated by similar aged detrital and metamorphic zircon in respective cover sequences and basement orthogneiss. MetaE-mail: g.phillips2@pgrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

GEOLOGY OF THE CLEMENCE MASSIF, CENTRAL PRINCE CHARLES MOUNTAINS, EAST ANTARCTICA A. F. CORVINO and C. J. L Wilson School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

Geologic data has been obtained sporadically from the Prince Charles Mountains (PCM) by Australian and Soviet workers since the late 1950's. These data have provided evidence that the PCM comprises of at least two main subdivisions: (i) a northern sector that underwent significant orogenesis at c. 990900 Ma, and; (ii) a southern sector composed of Archaean to Palaeoproterozoic crustal fragments partly reworked during the Cambrian. Whilst it is outwardly clear that these two domains have experienced unique geologic histories, the tectonic mechanisms governing their juxtaposition, and the timing of such events, have not been established. Moreover, the identity and extent of Cambrian age tectonism within the PCM remains contentious and it is not yet clear whether the consequence was either intra- or interplate orogenesis. This study presents geologic data for the little studied Clemence Massif located in the central PCM. The Clemence Massif is composed predominantly of strongly banded, migmatitic biotite-bearing felsic gneisses. The main geologic structure is a pervasive gneissic foliation that formed during metamorphism, along with anatexis, at suprasolidus temperatures. The rocks do not preserve conclusive evidence for multi-folding episodes {cf. surrounding exposures), nor do the microstructures confirm a polyphase prograde metamorphic evolution. A provisional

pressure-temperature (P-T) pseudosection, calculated for the bulk composition of a sillimanite-garnet pelite in the Na20-Ca0-K20Fe0-Mg0-Al203-Si02-H20 (i.e. NCKFMASH) model system, shows peak temperatures of 775-810°C were attained at about 7.5 kbar. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb analyses of zircon reveal that both Neoproterozoic and Cambrian ages are ubiquitous in rocks of pre-, syn- and posttectonic origin, an observation that is unique within the PCM. Igneous zircon cores from a pre-tectonic felsic orthogneiss record a mean age of c. 1060 Ma, whereas metamorphic rims yield exclusive Cambrian-Ordovician ages of c. 535-464 Ma. Metamorphic-type zircons from a syn-tectonic leucogneiss, interlayered with semi-pelite, record a dominant age of c. 910 Ma along with some Cambrian age growth. Zircon cores from a post-tectonic, intrusive pegmatite record scattered ages of C.1116-828 Ma and are overprinted by rims of Cambrian age. The available evidence can be used to propose: (i) emplacement of the felsic orthogneiss protolith at c. 1060 Ma; (ii) deposition of paragneiss protoliths, with abundant c. 990-900 Ma zircon detritus, during the Neoproterozoic, and; (iii) hightemperature metamorphism and intrusive activity during the Cambrian.

Keywords: Clemence Massif, Prince Charles Mountains E-mail: a.corvino@pgrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 3

Sedimentology and Palaeoecology

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

TRACE FOSSILS ON ECHINOID SKELETONS FROM THE OLIGOCENE-MIOCENE ABRAKURRIE LIMESTONE, EUCLA BASIN, WESTERN AUSTRALIA S. K. MARTIN School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

calcarenite, consisting of a number of cyclical sediment packages deposited in variable energy and water-depth conditions. One of the most important fossil groups in the unit are the echinoids, which form a diverse, specimen rich, assemblage whose preservation appears little influenced by taphonomy. The tests of irregular echinoids within this assemblage commonly preserve trace fossils; 13 separate morphologies have been recognised, including examples of predational, postmortem, and possibly parasitic interactions. The trace morphologies have been variously interpreted to represent perhaps seven groups of interacting organisms, including bryozoans, gastropods, bivalves and serpulid worms. A number of these organisms do not occur as body fossils in the unit, and as a result are identified exclusively through their traces. The distribution of these trace fossils may also provide useful information on the life-histories of host echinoid species.

Of all the aspects of palaeoecology, studies of behaviour and community dynamics are perhaps the most difficult to quantify. As body fossils can provide little information on how an organism interacted with its environment or other organisms, trace fossils have become an increasingly important tool to the palaeoecologist, particularly in studies of marine benthic groups such as the bivalves, gastropods, and echinoderms. Feeding trails, burrows, and resting traces made in sediments can often be used to interpret the way an organism fed or lived, particularly when compared with traces and trails found on the modern sea-floor. This study concentrates on another type of trace fossil of considerable interest to the palaeoecologist those traces made directly into or onto the surface of a body fossil, such as boreholes and encrustations. The Late Oligocene - Early Miocene Abrakurrie Limestone of the Eucia basin, Western Australia, is a highly fossiliferous

Keywords: Oligo-Miocene, echinoid, palaeoecology, taphonomy, Abrakurrie Limestone, Western Australia E-mail: Sarah.Martin@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

THE CHATHAM ISLAND'S TAKATIKA GRIT, CRETACEOUSTERTIARY (K-T) BOUNDARY SUCCESSION C. p. CONSOLIand J. D. Stillwell School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

The remote Chatham Islands preserve a unique window into the Late Cretaceous-Early Tertiary record of Greater New Zealand. The archipelago is approximately 860 km east of Christchurch, South Island, New Zealand, on the eastern extremity the Chatham Rise-a continental extension of New Zealand. These islands are the only emergent remnant of the rise that for much of the Cretaceous was a forested landmass in the proto-South Pacific. The preserved fossil fauna and flora is essentially a Gondwanan relict, and linked closely with the final fragmentation of Gondwana and concomitant changes in tectonic regime in the New Zealand Chatham Islands region in concert with prevailing palaeogeography and oceanic circulations. This biotic and geologic record is preserved fossil-rich horizons of the Takatika Grit, which straddles the K-T boundary. The unit is made up of glauconitic, quartzofeldspathic sandstones and abundant, large phosphorite nodules. It represents the basal succession of a transgressive system

resulting in a lag-style accumulation over a long period spanning the K-T boundary (midCampanian - early Palaeocene) (Wilson et al. 2005). Assemblages collected and identified thus far include: 1) theropod dinosaurs; 2) marine reptiles; 3) diverse sharks and teleost remains; 4) macroinvertebrates (ammonites, nautiloids, bivalves, gastropods and sponges; and 5) wood, cones and shoots. Importantly, there is now firm evidence from preliminary work that supports the eastward extension of a land bridge that connected with what is now New Zealand prior to the end of the Mesozoic. Furthermore, the Chatham's fauna and flora inhabited a high-latitude, temperate environment, the oceans surrounding were highly productive, supporting a diverse fauna. Austral macrofossil accumulations during this period are rare; the K-T marine succession on the Chatham Islands provides a good record of Gondwanan terrestrial and marine biotas and preserves a unique geological history in a poorly understood region of the Southern Hemisphere.

Keywords: Chatham Islands, New Zealand, Cretaceous-Tertiary Boundary, fauna, flora. palaebiogeography, sedimentology E-mail: christopher.consoli@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

THE PALAEONTOLOGY AND ENVIRONMENTS OF THE PLIOPLEISTOCENE WHITE SMOKERS OF THE CAPE VANI Mn DEPOSIT ON MILOS, GREECE J. M. C0FFEY\ S. J. Gallagher\ I. R. Plimer^ and T. H. Rich^ ^ School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia ^ Museum Victoria, GPO Box 666, Victoria 3001, Australia

absence of any planktonic foraminifera, this assemblage is typical of inner shelf palaeodepths from around 10 to 50 m. The occurrence of this fauna with echinoderm spines indicates an open marine setting with normal salinity levels. The associated coarsegrained burrowed facies with horizons of symmetrical ripples and hummocky cross stratification and a macrofauna of molluscs such as pectinids, Mytilus, fish teeth also indicates a shallow marine setting. However, the presence of three horizons of terrestrial artiodactyl megafauna (the first discovered on the island of Milos) in tuff horizons and trough cross laminated fluvial deposits suggests close proximity to the shoreline and regressive events in the sequence. The sequence is unconformably overlain by coarse-grained alluvial fan to braided river deposits deposited when the present island of Milos emerged from the sea.

The Cycladic island of Milos, 150 km southeast of Athens is in the active volcanic Aegean Arc. The island is dominated by Pliocene to Recent explosive calc-alkaline volcanics. Cape Vani is situated in the northwest of Milos, 20 km from Adamas. It is a maganese deposit hosted by volcaniclastic sandstone in a 1 km^ east-west-trending rift basin between two dacite intrusives. The Pliocene to Pleistocene succession hosts the only outcropping marine white smoker deposits on the earth's surface. While these volcanoclastic deposits are extensively hydrothermally altered, they yield a variety of micro- and macrofossils and exhibit primary depositional textures. Our study aims to chart depositional environments and history of this manganese deposit. The typical microfaunal assemblage of the strata of Cape Vani consists of Miliolinids (such as Quinqueloculina spp. and Triloculina spp.) and Elphidiids (Elphidium spp.). In the

Keywords: Milos, manganese deposit, white smoker, palaeontology E-mail: j.coffey@ugrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environnnental Sciences Conference The University of Melbourne, September 2005

MARINE GEOLOGY OF THE PLIOCENE TO RECENT BASS CANYON, SE AUSTRALIA J. K. MITCHELL, G. R. Holdgate, M. W. Wallace and S. J.Gallagher School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia The Bass Canyon is one of the world's largest submarine canyons, located on Australia's southeastern continental margin in the coolwater carbonate Gippsland Basin. Up to 2500 m of Oligocene-Recent marine carbonates are preserved within the Gippsland Basin Seaspray Group, and provide the seal to Australia's main hydrocarbon producing Latrobe Group. High velocity zones associated with Miocene submarine canyons within the Seaspray Group have caused significant time/depth conversion problems for exploration, leading to many off-structure wells. This study describes the modern Bass Canyon system and sedimentary processes as a potential analogue for the Miocene canyoning events. The modern Bass Canyon system consists of five shelf-breaching tributary canyons that coalesce on the lower-slope, entering the head of the massive deep-water Bass Canyon at 3000m depth. Various stages of canyon development from initiation to burial are recognised from analysis of high resolution swath-mapping and backscatter data, and piston core and surface sediment samples. These include; slope-confined pre-canyon ridge and channels; mature shelf-breaching canyons; and slope-confined partially buried canyons. Sediments and seafloor morphology suggest that slope-confined ridge and channels develop into immature canyons by headward erosion. Canyon maturity is

reached when the shelf is breached and coarse-grain shelf sediments are tapped. Headward erosion is triggered by up-slope sediment gravity flows (SGF) and density currents. Two types of mature canyons are recognised; actively eroding steep V-shaped canyons, and non-erosional smooth U-shaped canyons. Shallow seismic (<500ms TWT) across the outer-shelf and canyon heads, correlated to biostratigraphically controlled bores, reveals that the modern canyon mophologies developed in the latest Pliocene, subsequent to a period of increased (biogenic) sedimentation across the shelf and upperslope. Erosion was later amplified by Pleistocene eustatic fluctuations. Canyons incised within pre-existing late Neogene canyon structures, eroded by up-slope originating SGF. Increased SGF were likely to be caused by over-steepening of the shelfbreak following increased sedimentation rates and intensification of the local Bass Cascade density current during the late Pliocene. The onset of major canyoning in the late Mid Miocene may also have been induced by failure of over-steepened sediments, caused by increased biogenic production, possibly in response to favourable oceanic conditions. Such conditions were likely to have been promoted by strong upwelling events and development of the Antarctic Circumpolar Current.

Keywords: Submarine canyon, cool-water carbonate, swath mapping, sediment gravity flow, density current, headward erosion, sedimentation rate

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

INSECTS OF THE EARLY JURASSIC CATTAMARRA COAL MEASURES, WESTERN AUSTRALIA: PINPOINTING THE ORIGINS OF A MODERN FAUNA S. K. MARTIN School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

Fossil insects have been known in Australia since the description of a dragonfly wing from the Cretaceous of Queensland by Woodward in 1884. Despite this first discovery, Jurassic and Cretaceous insect localities are relatively rare on this continent. This contrasts with the Northern Hemisphere, where rich Jurassic lagerstatten and Cretaceous ambers have yielded detailed insights into insect taxonomy and palaeoecology. The Jurassic insect fauna of Australia is especially poorly known, with only two insect taxa, from two different units, formally described. Worldwide, the Jurassic is characterised by a dramatic faunal changeover in insects, with ancient Carboniferous and Permian groups disappearing in favour of modern insect forms. As a result, the description and interpretation of Australian Jurassic insects takes on even greater importance as it may provide the key to understanding the origins and evolution of modern insect faunas worldwide. The insect fauna of the Early Jurassic Cattamarra Coal Measures in Western Australia will be studied in an attempt to

partially rectify this lack of knowledge. It not only provides the most extensive assemblage of fossils from an important and unknown period of Australian insect evolution, but also represents the only insect assemblage recorded thus far from the western half of the continent. The insects are preserved as twodimensional impressions in the sediment, usually consisting of disarticulated, fragmented and compressed elements, particularly wings and elytra. The assemblage is characterised by adult terrestrial insects which have presumably fallen into the water body and been transported to the deposition site. This preservation style, common for fossil insect assemblages, supports the fluvialdeltaic interpretation for sediments of this unit. Although only fragmentary insect remains have been found so far, it is hoped enough material will be recovered to allow a reasonable palaeoecological and palaeoenvironmental study. Taxonomically, the Cattamarra Coal Measures assemblage is dominated by the Coleoptera (beetles) and Blattodea (cockroaches).

Keywords: Jurassic, fossil insects. Western Australia E-mail: Sarah.Martin@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

MODERN SEAFLOOR ENVIRONMENTS (SEDIMENTARY, FORAMINIFERAL & OSTRACODE) OF THE PITT WATER ESTUARY, SOUTH-EAST TASMANIA D. C. LEWIS School of Earth Sciences, University of Tasmania, Tasmania 7001, Australia The Pitt Water Estuary is a shallow, barrier estuary, with typically normal marine salinity which is subject to dilution during floods. The distribution of sedimentary facies and foraminiferal and ostracod assemblages, examined from surficial sediment samples, was used to describe seafloor environments of the estuary. Ten sedimentary facies were identified, by grouping sediment samples on the basis of particle-size and lithic sand content. Cluster analysis of foraminiferal and ostracod data produced twelve benthic foraminiferal and eight ostracod sample associations. The distribution of sedimentary facies varies, firstly, with the upstream change in relative current energy (tidal versus fluvial) as reflected by the relative proportion of quartzose to lithic sand in sediment; and, secondly, with the water depth variation in current strength, as reflected by the sand grain size and mud content. The distribution and composition of foraminiferal and ostracod assemblages is determined mainly by average salinity and pH. The position of species along the axis of the

estuary correlates with the altered salinity profile which occurs during floods, with tolerance to lowered salinity being greater further upstream. Low pH conditions are widely distributed (due to the anoxicity of stagnant waters), causing calcareous test dissolution which, in deeper waters of the upper estuary and Orielton Lagoon, totally excludes calcareous foraminifera and ostracods. Illumination is also important in controlling ostracod distribution, being lowest in the highly turbid waters of the upper estuary and Orielton Lagoon. Additional factors controlling foraminiferal and ostracod distribution include: substrate mobility (of intertidal zone and channels), nutrients, seagrass distribution, tidal exposure, and tolerance to varying temperature. Anthropogenic influences occur on the seafloor environments of the estuary, with catchment land use, river dam construction and irrigation activities, and causeway construction, leading to increased mud and nutrient supply, altered natural river flow regime and volume, and emplaced artificial boundaries to tidal exchange.

Keywords: Pitt Water Estuary, foraminifera, ostracoda, sediments, seafloor environments E-mail: dcjewis@utas.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

PALYNOLOGICAL EVIDENCE OF VEGETATIONAL CHANGE IN EARLY CRETACEOUS SEDIMENTS, GIPPSLAND BASIN, VICTORIA D. E. SEEGETS-VILLIERS School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

Cyathidites australis and Baculatisporites comaumensis. Amongst the canopy forming species, only the gymnosperm Cycadopites nitidus is consistently present, however, usually at a much lower percentage than the ferns. Ground covering floral elements such as hepatics and mosses are either entirely missing or only represented in very small numbers. The lycopod genus Retitrilites and, to a lesser extent, the gymnosperm Araucariacites australis are the two taxa that show the most obvious variation in some of the areas studied, perhaps indicating climate driven vegetational change.

The Early Cretaceous high latitude deposits of the Flat Rocks Fossil Site at Inverloch, Victoria are well known for their diverse and abundant vertebrate fossil fauna. Plant material, although consistently present in coal and organic layers and as scattered debris throughout the sediments at the site, has, so far not been studied extensively. This study deals with the examination of the palynological content of several locations in the vicinity of the fossil vertebrate site and its palaeoenvironmental implications. All localities selected for palynological investigation show an overall high presence of fern species such as Cyathidites minor,

Keywords: Early Cretaceous, Gippsland Basin, palynology E-mail: Doris.Seegets-Villiers@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 4

Economic and Mine Geology

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

THREE DIMENSIONAL MODELLING OF GOLD MINERALISATION IN THE WOODS POINT DISTRICT, VICTORIA N. P. THORP, L Ailleres and F. P. Bierlein School of Geosciences, Monash University, Clayton, Victoria 3800, Australia creating faulted pathways and low-pressure zones where minerals could precipitate. This process lead to the situation seen at the Loch Fyne and A1 deposits where mineralisation is confined to alteration halos along fault hosted, laminated quartz reefs. Within these halos, zones of rich mineralisation occur at points of greater than normal dilatancy such as at fault intersections and changes in fault geometries. Increased gold grades were also recorded along the margins of the quartz reefs near the dyke-sediment interfaces, suggesting a redox front was also partially responsible for gold deposition. Further work using fluid flow and mechanical modelling is being undertaken in an attempt to constrain the tectonic stress regimes that could have been responsible for dyke bulge emplacement and mineralisation at the Loch Fyne and A1 gold deposits.

The Woods Point district covers the northern portion of the Walhalla-Woods Point goldfield, historically the most significant goldfield in the Melbourne Zone. Mineralisation in the field is associated with quartz reefs that are hosted by reverse faults created during the Tabberaberan Orogeny. Host lithologies are confined to the more component units in the field, either the intrusives of the Woods Point Dyke Swarm or the turbiditic sandstones of the Early Devonian Walhalla Group. New research involving three-dimensional modelling, historical literature reviews and fieldwork at two significant dyke-hosted sites of mineralisation (the A1 and Loch Fyne deposits) has revealed important relationships between structure, lithology and mineralisation within the dyke-hosted deposits. Fracturing of the competent dyke appears to have concentrated auriferous hydrothermal fluids by

Keywords: gold mineralisation. Woods Point, A1, Loch Fyne, Victoria, structurally controlled mineralisation, three-dimensional modelling

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

CONSTRAINING THE GEOLOGY OF BROKEN HILL, NSW, AUSTRALIA, IN THREE DIMENSIONS USING GEOPHYSICAL METHODS AND INVERSION TECHNIQUES A. MCLELLAN, L. Ailleres and R. Weinberg Australian Crustal Research Centre, Monash University, Victoria 3800, Australia

This investigation focuses on constraining the three dimensional geology of the Broken Hill area, NSW, using coupled geophysical inversion techniques on classically accepted geological models. The Broken Hill domain comprises a complex package of Palaeoproterozoic rocks known as the Willyama Supergroup. The area has undergone up to five deformation phases during the Olarian and Delamarian orogenies, which has caused significant deformation and metamorphism of the dominantly metasedimentary rocks. The complex nature and structure of the rocks has given rise to several different theories regarding the

tectonic evolution and history of the Broken Hill domain. Here, these theories are put to the test by applying geophysical data, in the form of both gravity and magnetic surveys, to three-dimensional models built using the geoscientific software package SDGeomodeller. In depth analysis of petrophysical properties of the various units in the Broken Hill domain reveal the complex nature and difficulties encountered whilst inverting potential field data in Broken Hill. Inversion calculations were carried out on all the models proposed in this investigation, with results suggesting revision of the proposed models is needed.

Keywords: SDgeomodeller, 3D modeling, geophysics, inversion, Broken Hill, gravity E-mail: Andrew.McLellan@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, Septennber 2005

AMPHIBOLITES OF THE EASTERN SUCCESSION, BROKEN HILL, NEW SOUTH WALES R. E. O'Sullivan School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

common, suggesting a lava, air-fall tuff or sill origin. Few contacts transgress bedding, indicating intrusive dykes (e.g. feeder dykes). Sheared contacts result from lithological competency differences of enclosing metasediments during deformation and highgrade metamorphism. Gradational boundaries from amphibolite to garnet-spotted amphibolite to felsic amphibolite gneiss were also recorded with relatively higher magnetic susceptibility readings recorded in felsic amphibolites. Preliminary geochemical data support previous work that amphibolites were originally Fe-rich tholeiitic basalts. Further analysis aims to investigate whether magnetite and Fe-enrichment was primary or secondary and can be attributed to fractional crystallisation, premetamorphic alteration or a combination of both. Developing an understanding of the eastern succession relationships in relation to the western succession will facilitate exploration for further mineralisation on Consolidated Mining Lease 7.

The Broken Hill Main Lode is hosted by the Broken Hill Group of the Palaeoproterozoic Willyama Supergroup which has undergone polyphase deformation and coeval high-grade metamorphism. The Main Lode lies on the northwest limb of the Broken Hill Antiform and, until this year, extensive drilling has been orientated towards the west, targeting the Main Line of Lode. After more than 120 years of mining the world's largest base-metal deposit at Broken Hill, the eastern sequence remains unexplored. Only four holes have previously been drilled through the eastern limb of the Broken Hill Antiform. Magnetic susceptibility logging of three eastern cores drilled through CBH Resources Ltd, Consolidated Mining Lease 7 revealed a salient difference between the east and west successions. The eastern succession is highly magnetic relative to the western succession and this asymmetry is especially pronounced the amphibolites. The amphibolites logged display sharp, sheared and gradational contacts. Sharp contacts conformable with bedding are most

Keywords: Broken Hill, amphibolite, Willyama Supergroup, Broken Hill Group, magnetic susceptibility, fractional crystallisation E-mail: rhondaeo@hotmail.com

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

THE GEOCHEMICAL AND HYDROGEOLOGICAL CHARACTERISTICS OF AN ABANDONED TAILINGS DAM AT SAVAGE RIVER MINE, TASMANIA T. H A S S E L L \ J. A. Webb^ a n d D. Ray^ ^ Department of Environmental Geoscience, La Trobe University, Victoria 3086, Australia ^ Department of Primary Industries, Water and Environmental, Tasmania 7001, Australia Savage River Mine is situated in northwestern Tasmania in a region with rugged topography, high consistent rainfall and low evaporation. The magnetite ore body lies along the Arthur Lineament and is surrounded by magnesite, calcite-chlorite schist, and pyrite-rich metabasalt schist. The ore is dominated by magnetite and pyrite, with minor amounts of chalcopyrite and rutile. Mining, which began in 1967, is open-cut; the ore is concentrated on site before being pumped to the north coast. The Old Tailings Dam at the mine was constructed in 1967 and used as the main disposal site for pyrite-rich tailings produced at the mine until 1982. The surface of the tailings slopes from the dam wall in the south towards a reservoir in the north. Approximately 0.7 km^ of the tailings are sub-aerially exposed, and another 0.2 km^ lie beneath the reservoir. Any runoff generated on the sub-aerially exposed tailings during rainfall events collects in the

reservoir, and overflow runs into Savage River. The dam wall has several acid seeps draining from the base. These seeps run into two lakes on the east and west sides of the dam wall. The acid seepages are a serious environmental issue at the site, and the purpose of this study was to determine the origin of the acidity through a detailed study of the hydrogeology and geochemistry of the tailings. Tritium dating revealed that water discharging from the seeps in the southern dam wall is - 1 2 years old. The seeps contain significant concentrations of Fe, Co, Mn, Zn, Al and traces of Ni; these elements are not present in such high levels in groundwater within the tailings. This indicates that the source of heavy metals in the seeps is likely to be the waste rock used to construct the dam wall, rather than the tailings contained within the dam.

Keywords: acid mine drainage. Savage River, tailings, hydrogeochemistry E-mail: Lhassell@latrobe.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

INVESTIGATING THE THERMAL STATE OF THE CRUST, A MODEL FROM WESTERN VICTORIA D. V. WIJERATNE and G. R. Beardsmore School of Geosciences, Monash University, Clayton, Victoria 3800, Australia measurements. Temperature logs collected from 17 groundwater bores in the study area reveal average temperature gradients of 4 0 60 K/km. The highest gradient of 55 K/km is found in the Gellibrand Marl within the Oligocene-Miocene aged Heytesbury Group. Combining thermal gradient data with thermal conductivity measurements allows heat flow values to be calculated for each formation. These values can be used to predict temperature distribution throughout the region, constrain potential geothermal reservoirs, and guide further exploration in the area.

"Geothermal energy" refers to the Earth's heat, which can be harnessed for electricity generation or direct use. Investigating the thermal and geological structure of Western Victoria are major components in evaluating the region's potential as a geothermal resource. Producing a heat flow model is a major step in this process. The study area lies between Terang in the west, Geelong in the east, Colac in the south and Cressy in the north. Heat flow values can be measured using techniques such as temperature logging and thermal conductivity

Keywords: heat flow, geothermal energy, temperature logging, thermal conductivity E-mail: dvwiji@student.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

MINERAL EXPLORATION UNDER COVER: 3D MODELLING OF GOLD MINERALISATION, WALHALLA, VICTORIA M. H O U G H \ L A i l l e r e s \ F. P. B i e r l e i n ^ C, W i l l m a n ^ A, Seymon^ a n d S-Hutchin"^ ^ School of Geosciences, Monash University, Clayton, Victoria 3800, Australia ^Tectonics Special Research Centre, School of Earth and Geographical Sciences (M004), The University of Western Australia, Crawley WA 6009 ^Geoscience Victoria, Melbourne, Victoria 3000, Australia "^Goldstar Resources NL, Rawson Victoria 3825, Australia Victoria is host to one of the world's major orogenic gold provinces, having produced approximately 2,500 tonnes of gold since the 1850's. The focus of this project is on the historic township of Walhalla within the Wood's Point - Walhalla goldfield, 150 kilometres east of Melbourne. Research is concentrated on selected gold deposits near Walhalla in response to the latest GeoScience Victoria mapping initiative and current exploration by Goldstar Resources NL. The aim is to understand the origin, genesis and differing styles of gold mineralisation in relation to the major structural features of the Melbourne Zone and more broadly, the evolution of the Lachlan Orogen. The prediction of favourable sites of gold mineralisation is an additional research aim. The differing ore systems include laminated-massive quartz veins (eg. Cohen's Reef), fissure lodes (e.g. Longfellows Mine), dyke-related ladder veins (e.g. Tubal Cain), and stockwork-hosted and disseminated occurrences within intrusive and/or

metasedimentary host rock. The ore systems within the region are associated both spatially and temporally with the emplacement of the Woods Point Dyke Swarm. The development and testing of 3D models of the ore systems will involve the integration of available datasets including historical information, surface and mine geology, drill core data and geochemistry. Geochemical sampling will focus on the extent and shape of hydrothermal alteration haloes, to delineate ore bodies and hydrothermal fluid systems, and to aid visualisation and analysis of important relationships. Geological surfaces and volume properties such as porosity and permeability will be modeled in 3D, allowing for the eventual development of chemical and thermodynamic fluid models. Ultimately, the unique interplay of the host rock geology, the structural framework, magmatism and mineralisation styles need to be understood to resolve the mechanisms for gold emplacement in the selected deposits around Walhalla, and allow for the development of predictive exploration models.

Acknowledgements: Research is supported by funding from ARC Linkage Project (LP0560511), and collaborative partners, Goldstar Resources NL and GeoScience Victoria Keywords: orogenic gold, Walhalla, 3D visualisation E-mail: Megan.Hough@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

DIRECT DATING OF ORE MINERALS: A FEASIBILITY STUDY OF THE Pb-Pb ISOTOPE STEP-LEACHING TECHNIQUE K. BASSANO, J. Hergt, R. Maas and J. Woodhead pmd*CRC, School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia - obtain 'single'-mineral isochron ages without the need for analysing associated minerals to produce isotopic dispersion on isochrons. This study builds on previous observations and tests the reliability of PbSL in directly dating ore minerals such as sulfides (chalcopyrite, pyrite, pyrrhotite/pentlandite) and oxides (magnetite), thereby obtaining the timing of mineralisation from a phase that is unambiguously linked to the ore-forming process. This is based on the often surprisingly high U contents (relative to what might be anticipated), yielding rather higher than expected initial U/Pb ratios in several types of low-Pb sulfides. The technique is applied to well-constrained samples from a number of predominately Australian mineral deposits covering a range of mineralisation types.

Pb-Pb step-leaching (PbSL) is a digestion technique based on sequential acid treatment of a mineral resulting in the selective recovery of radiogenic and common Pb components from the crystal lattice, making single-phase Pb-Pb dating possible. Developed originally by R. Frei and colleagues at Bern, the technique was recently applied to Proterozoic garnets to test the reliability of PbSL as a dating tool in multiply deformed terranes. Benefits of PbSL over bulk U-Pb and PbPb techniques include the ability to: - detect sub-microscopic U-rich inclusions using the distinct variations in ^^^Pb/^^^Pb (i.e. time-integrated Th/U) between host mineral and inclusions such as zircon or monazite; - date a wide range of minerals with low-U; minerals generally thought to be unfavourable for conventional U/Pb dating; and

Keywords: Pb-Pb, step-leaching, ore minerals, direct dating

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 5

Vertebrate Palaeontology

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

DIVERSITY AND NOVELTY IN THE EARLY EVOLUTION OF BALEEN WHALES (MAMMALIA: CETACEA: MYSTICETI) E. M. G. FITZGERALD School of Geosciences, Monash University, Clayton, Victoria 3800, Australia Museum Victoria, GPO Box 666, Victoria 3001, Australia

mysticetes are all inferred to have used, at the least, an incipient filter-feeding method to acquire prey, employing baleen, teeth, or "proto-baleen". Thus, all extant, and most fossil, mysticetes occupy a restricted ecomorphospace, being generally large, pelagic, filter-feeders. Fossils from the Late Oligocene of Victoria (Australia) add important insights into the early evolutionary history of Mysticeti. These toothed mysticetes, classified in the Family Mammalodontidae and a new, undescribed family, possess morphological adaptations previously unknown in Mysticeti. None of the Victorian toothed mysticetes appear closely related to the Southern Hemisphere Llanocetidae, or Northern Hemisphere Aetiocetidae and an undescribed family from South Carolina, U.S.A. Compared to the Aetiocetidae, and the new family from South Carolina, the Victorian toothed mysticetes possess derivative, highly novel, cranial morphology. There is no evidence for the possession of baleen or "proto-baleen" in the Victorian toothed mysticetes. These data suggest that the Victorian toothed mysticetes employed markedly different feeding strategies to those of their Northern Hemisphere contemporaries, and all other known mysticetes. Furthermore, it indicates that the early evolutionary history of baleen whales was characterised by greater degrees of diversity and disparity than previously thought.

Mysticetes (Order Cetacea: Suborder Mysticeti) are often described as the baleen whales. This vernacular name stems from the unique feeding device that all extant mysticetes possess: baleen. Baleen is a hairlike structure composed of the protein keratin, which is arranged as plates growing from the epidermis in the palate. This remarkable structure is used to sieve, or filter, planktonic organisms from seawater, which is ingested en masse. Although there are three distinctive filter-feeding methods that the four extant families of mysticetes employ, they are all united by the use of baleen to capture prey in bulk. The origins and evolution of this highly derived feeding mechanism, as well as the mysticetes themselves, have remained enigmatic due to a generally poor fossil record during the Oligocene (--23-34 Ma). It is during the Oligocene that the modern cetaceans, the mysticetes and their close relatives the odontocetes (Suborder Odontoceti, toothed echolocating whales; e.g. dolphins, porpoises, sperm whales), supposedly undenA/ent a significant adaptive radiation. Available fossil evidence from the latest Eocene through Late Oligocene has indicated that there were a number of extinct families of mysticetes during this time. These fossil mysticetes include both archaic baleen-bearing mysticetes (e.g. Eomysticetoidea, Mauicetus), and more primitive toothed mysticetes (e.g. Aetiocetidae, Llanocetidae). Despite being more archaic (and generally smaller) than their extant relatives, these Oligocene

Keywords: Cetacea, Mysticeti, Aetiocetidae, Llanocetidae, Mammalodontidae, toothed mysticetes, Oligocene, Australia, evolution E-mail: efitzger@museum.vic.gov.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

A COMPARATIVE ANATOMY OF PALORCHESTES AZAEL (MARSUPIALIA: DIPROTODONTOIDEA: PALORCHESTIDAE) FROM THE BUCHAN CAVES REGION, NORTHEAST VICTORIA D. A. SHEAN^ and J. Hellstrom^ ^School of Geosciences, Monash University, Clayton, Victoria 3800, Australia ^ School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

Palorchestes azael is the largest member of the Palorchestid family and also the youngest. The species, Palorchestes azael, has been well documented since the late century, however very little is understood about the cranial structure, including nasal and orbital region, cranial vault and degree of sinus development. In 2004 a cranium of P. azael was recovered from the Palaeo Pot Cave, Buchan, in the northeast of Victoria. This specimen represents an important advance in our understanding of the cranial morphology of P. azael, as many of the previously unknown elements are observable. The brain case, basicranium and auditory regions are intact, as are the mandible and maxilla; internal nasal structures, palatine and pterygoid are absent. The cranium has a high

lateral profile and is square in dorsal profile. The cranium displays many characteristics comparable to the older species, Palorchestes painel, and Propalorchestes novaculocephalus, such as an enlarged glenoid fossa, abbreviated post glenoid process and similar parietal and squamosal structure. The cranium displays exaggerated vaulted internal chambers anterior to the braincase that are similar to those of Diprotodon optatum. The cranium has been dated at greater than 0.275 Ma ± 0.003 on the basis of mass spectrometric U/Th isotopic analysis of calcite surrounding the cranium. This age is consistent with recorded occurrences of P. azael in South Australia, and New South Wales.

Keywords: Palorchestes azael, cranial morphology, Diprotodon optatum, Palorchestes painel, Propalorchestes novaculocephalus. E-mail: Danielle.Shean@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

NEW FOSSIL CROCODILE MATERIAL FROM THE EOCENE KEROSENE CREEK MEMBER, RUNDLE FORMATION, QUEENSLAND L A. BUCHANAN School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

New fossil crocodile material recovered from the Rundle Formation in southeastern Queensland is identified as Kambara, the earliest known genus within the endemic Australasian Mekosuchinae. The material was recovered from freshwater, lacustrine deposits of Eocene age and indicates that Australian crocodilians were beginning to develop the diversity seen in the late Tertiary within this early genus. Differences noted between the new material and previously described Kambara species in the both the skull and lower jaw are largely related to their dentition and kind of bite of the crocodiles. The new material has a well developed interlocking dentition, a feature that has been explored by other species within this genus, though the degree development seen in the new material is only present in one other

species, K. /rnp/ex/c/ens Salisbury, 1996. The back of the lower jaw has a broader area of attachment for various parts of the M. pterygoideus posterior, a muscle involved in jaw closure. This heterogeneity of skull and lower jaw morphology indicates that early Tertiary crocodilians may have been far more diverse than initially expected, providing new insights into origin and early evolutionary pathways of this unique group of crocodiles endemic to Australia. Mekosuchinae was originally classified as a subfamily to Crocodylidae, though Salisbury (1996) noted that this relationship was problematic. As this relationship is yet uncertain features of this new species provide greater insight into not only this genus but also the overall relation of Mekosuchinae to Crocodylidae.

Keywords: Rundle Formation, Kerosene Creek Member, Tertiary, Eocene, Mekosuchinae, Kambara E-mail: Lucas.Buchanan@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environnnental Sciences Conference The University of Melbourne, September 2005

PRELIMINARY TAPHONOMIC AND PALAEOENVIRONMENTAL INTERPRETATIONS OF THE EARLY PLEISTOCENE NELSON BAY LOCAL FAUNA, PORTLAND, VICTORIA K. J. PIPER School of Geosciences, Monash University, Clayton, Victoria 3800, Australia bone by roots is evident on many of the specimens. Gnaw and bite marks are present on a large proportion of the postcranial specimens, particularly the distal limb elements indicating scavengers and/or predators were influential in the disarticulation of carcasses. There is little evidence of the transport or sorting of elements by water. The fauna, which contains at least 27 species of marsupial and three species of rodent, is rich in browsers and arboreal animals, suggesting the environment was wooded or forested. Continued analysis aims to further clarify the depositional and taphonomic history of this interesting fauna.

The majority of the fossil mammal specimens that comprise the early Pleistocene Nelson Bay Local Fauna have been collected from the upper clay bed (B2) of unit B of the Nelson Bay Formation. This bed, which outcrops along the base of sea cliffs in Nelson Bay near Portland, Victoria, is composed of an orangebrown silty clay, rich in organic matter, rootlets, and terrestrial and freshwater gastropods. At least where it is exposed in the western part of the bay it is interpreted as a palaeosol horizon. The types of vertebrate fossil elements preserved and the bias towards teeth is consistent with this interpretation. Etching of the tooth enamel and

Keywords: Nelson Bay, taphonomy, Marsupialia, Pleistocene E-mail: kat.piper@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

A HETEROCERCAL CAUDAL FIN FROM DINOSAUR COVE, OTWAY GROUP, VICTORIA (EARLY CRETACEOUS: APTIAN ALBIAN), IDENTIFIED AS PSILICHTHYS CF SELWYNI HALL, 1900 (ACTINOPTERYGII: PALAEONISCIFORMES) M. P. INGLIS School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

the genus, previously known only by the holotype. While the familial affinities of Psilichthys remain uncertain, the fact that it is a primitive palaeonisciform is significant Most palaeonisciform genera went extinct by the start of the Cretaceous, so Psilichthys was a late occurence of this once abundant group. This phenomenon is also seen in other fossil taxa, including dinosaurs, temnospondyls and some plants. The main reasons suggested for this are cold and isolation experienced by the region during the Early Cretaceous. Therefore, the study of Psilichthys has broader implications in both palaeontology and geology, including the areas of palaeobiogeography and palaeoclimatology.

A number of fossil fish remains have been uncovered at Dinosaur Cove (Latest Aptian Early Albian), Otway Group, Victoria, Australia. One of these specimens, found at the Slippery Rock Locality in March 1987, consists of a well-preserved partial caudal fin. This caudal fin is in the heterocercal condition, a feature common among the primitive Palaeonisciformes. The specimen was compared to the holotype of Psilichthys selwyni Hall, 1900, also from Early Cretaceous sediments of Victoria, and identified as Psilichthys cf selwyni. Although both specimens are incomplete, the characters preserved in each serve to complement each other, providing a more complete picture of the genus. The Dinosaur Cove specimen also provides a new locale for

Keywords: Actinopterygii, Palaeonisciformes, Psilichthys selwyni Hall 1900, caudal fin, heterocercal. Early Cretaceous, Dinosaur Cove, Otway Group, Victoria, Australia E-mail:

Matthew.lnglis@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environnnental Sciences Conference The University of Melbourne, September 2005

A REVIEW OF THE PLEISTOCENE VERTEBRATE FAUNAL ASSEMBLAGE AT BUCHAN, VICTORIA D. A. SHEAN School of Geosciences, Monash University, Clayton, Victoria, Australia

Macropus macropus giganteus and Phascolonus gigas (giant wombat). Regionally extinct arboreal faunas that existed in this region are Burramys parvus (mountain pygmy possum), Phascolarctos cinerea (koala) and Acrobates pygmaeus (feathertail glider). The fauna within this assemblage is varied and would have represented a number of differing habitable environments including open woodland, sclerophyll forests, grasslands and swampy alluvial plains. New research of postcranial material has introduced three new species into the assemblage: Ramsayia magna, one of the greater wombats, a Hypsiprymnodon-WWe marsupial and a possible new species of Protemnodon.

The Pleistocene vertebrate assemblage from Buchan is both diverse and fascinating, comprising many genera common to assemblages Australia-wide, but also some rare and unusual fauna. The most famous fossil species recovered from Buchan are the tapir-like large marsupials Palorchestes azael and P. parvus, and many other genera, now extinct in this region, coexisted with these species. Examples of predators of body size greater than 3kg include Thylacinus cynocephalus (Tasmanian tiger) , Sarcophilus harrisii (Tasmanian devil) and Thylacoleo carnifex fmarsupial lion). The most common browsers were short-faced macropodid faunas such as Sthenurus orientalis and Procoptodon gilli, and Palorchestes azael and P. parvus. Grazing faunas included Protemnodon anak,

Keywords: Buchan Caves, Pleistocene, mega fauna. E-mail: Danielle.Shean@sci.monash.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

A REVIEW OF CURRENT AUSTRALIAN FOSSIL CROCODILES AND MEKOSUCHINAE IN LITERATURE L A. BUCHANAN School of Geosciences, Monash University, Clayton, Victoria 3800, Australia New Caledonia and Fiji). The setting up of the Mekosuchinae provided a formalisation of what was previously being referred to as the Australian Tertiary crocodile radiation (Willis et al. 1990), a recognition of the significant degree of similarity seen between Tertiary Australasian crocodiles, distinguishing them from all others. Willis et al. (1990) noted the likelihood of an endemic radiation of crocodiles which diversified throughout the Tertiary. Apparently for whatever ecologic reason, crocodiles were able to exploit various niches not used by extant crocodiles. The Mekosuchinae includes the genera Kambara, Baru, Quinkana, Mekosuchus, Trilophosuchus, A ustralosuchus, Pallimnarchus, and possibly the enigmatic Harpacochampsa. The diversity seen in this clade is rather interesting as many different ecologic niches have been exploited by various members, ranging from the terrestrial Quinkana, to the aquatic giant Australosuchus, as well as the potentially arboreal Mekosuchus.

Australian fossil crocodiles have shown a surprising degree of diversity throughout the Tertiary. However, as well understood as Australia's extant crocodiles species are, and as widely revered as the giant Australian saltwater crocodiles {Crocodylus porosus) are, the fossil record has really only begun to take shape in the past twenty or thirty years (Willis 1993). Though the first record of fossil crocodiles from Australia is from Clarke (1869) in his reference to crocodile bones in Crinum Creek near Peak Downs in Queensland, and Daintree (1872) also noted crocodile teeth from Maryvale Creek, Queensland, the definition of the mekosuchine genera and species only began in the 1980's. Willis et al. (1993) used the definition of a new genus and species, Kambara murgonensis from the Eocene deposits at Murgon, Queensland, as a platform to create a new subfamily, Mekosuchinae. This new taxon was created to incorporate all Tertiary fossil crocodiles from Australia (excluding Crocodylus species) and some from surrounding South Pacific islands (such as

Keywords: Tertiary, Mekosuchinae, Kambara, Baru, Quinkana, Mekosuchus, Australosuchus, Pallimnarchus, Harpacochampsa E-mail: Lucas.Buchanan@sci.monash.edu.au

Trilophosuchus,

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Geological Society of Australia Abstracts

CHATHAM ISLANDS THEROPODS: DINOSAUR SANCTUARY FROM K-T BOUNDARY SUCCESION C. p. C O N S O L r , J. D. S t i l l w e l l \ R, S u t h e r l a n d ^ S. S a l i s b u r y ^ T. H. R i c h ^ P. A. V i c k e r s - R i c h \ P. J, C u r r i e ^ G. J, W i l s o n \ ^ School of Geosciences, Monash University, Clayton, Victoria 3800, Australia ^Institute of Geological and Nuclear Sciences, P. O. Box 30-368, Lower Hutt, New Zealand ^School of Life Sciences, The University of Queensland, Brisbane 4072, Australia ^Museum Victoria, GPO Box 666, Victoria 3001, Australia ^Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta TOJ OYO Canada

Dinosaurs from the K-T boundary sections of the Chatham Islands were recovered from the Takatika Grit on the remote Chatham Islands along the Chatham Rise, an eastern extension of South Island, New Zealand. The grit is glauconitic, quartzofeldspathic sandstone deposited within a marine environment. Representing a transgressive systems tract, the deposit is possibly an allochthonous accumulation of reworked uppermost Cretaceous fossils into the immediate post KT boundary Danian interval. Based on associated microfossil content, the unit is midCampanian to early Palaeocene in age; the microfauna is dominated by the midCampanian dinoflagellates, correlated to the Satyrodinium haumuriense Zone (Wilson, 2005). The theropod remains include a centrum, the proximal pedal phalanx 11-1 or IIIKeywords: Chatham palaeobiogeography

Islands,

New

1 of a theropod as well as the probable theropod proximal head of a tibia. Moreover, a theropod manual phalanx and manual ungual were collected stratigraphically above the major Cretaceous faunal assemblage. Tectonic and palaeontologic evidence support the existence of a large landmass, which extended eastward from New Zealand connecting the islands prior to the K-T boundary. The Chatham's terrestrial fauna inhabited high-latitude environments along this low-lying, crustal extension of the New Zealand subcontinent and together with other Late Cretaceous New Zealand dinosaur remains, it is now confirmed that a significant dinosaur population inhabited 'Greater New Zealand' providing a sanctuary after separating from the Gondwana margin ca. 80 Ma.

Zealand,

E-mail: christopher.consoli@sci.monash.edu.au

Cretaceous-Tertiary

Boundary,

dinosaur,

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 6

Geochemistry and Geodynamics

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

SPATIAL AND TEMPORAL EVOLUTION OF THE SUBDUCTING PACIFIC PLATE BENEATH NORTHEAST ASIA: EVIDENCE FROM TOMOGRAPHY AND PALEOGEOGRAPHIC RECONSTRUCTIONS M. S. MILLER and B. L N. Kennett Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

the oceanic lithosphere beneath the Kurile Arc is slightly thicker and is subducting at a steeper angle that penetrates through the transition zone into the lower mantle. We have investigated the difference in slab morphology along the arc in conjunction with a new palaeogeographic reconstruction of the Western Pacific based on Euler pole motions of the Pacific, Philippine, Amurian, Okhotsk, and North American Plates. Our tectonic reconstruction illustrates the collision of the Japan and Kurile Arcs, the opening of the Kurile Basin, disparity in Pacific Plate velocities along the arc, and trench retreat along different segments of the western margin. The new plate motion model and interpretations of the physical properties of the mantle imaged with the P-wave and joint tomography are used to assess the evolution of the Pacific Plate morphology since the midMiocene.

Plate motions and subducting slab morphology are intricately connected and through the combination of seismicity, tomographic images, and relative plate motions the evolution of mantle structure can be interpreted. Tomographic images of Pwave, shear wave-speed, and bulk sound speed perturbations of the Northwest Pacific region have been interpreted to define the extent and geometry of the subducting Pacific Plate. We have found that the subducted Pacific Plate beneath the Japan and Kurile arcs is coherent, but is very complex at the junction of the two arcs near the Hokkaido corner, as the slab subduction angle decreases from north to south while the slab thickens. The Pacific slab beneath the Japan Arc is subducting through the upper mantle at an angle of approximately 30° until it reaches the 660 km discontinuity where it becomes bends into a horizontal position. In contrast.

Keywords: seismic tomography, plate reconstructions, three-dimensional model, Pacific Plate, Japan-Kurile arc

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

INSIGHTS INTO MAGMA GENERATION AND EVOLUTION AT WHITE ISLAND, NEW ZEALAND Z. H E Y W 0 R T H \ R. M. G e o r g e ^ B. F. Schaefer^ a n d S. P. T u r n e r ^ ^ School of Geosciences, Monash University, Clayton, Victoria 3800, Australia ^GEMOC National Key Centre, Macquarie University, Sydney, NSW 2109, Australia crystallisation/equilibration depths (<3 km). However, such pressures are consistent with previous pressure estimates at Mt Ruapehu (0.5-7 kbars; Graham & Hackett 1987; Gamble et al. 1990) and a magma chamber depth of 2-7 km beneath White Island (Cole et al. 2000). Based on melt inclusion studies, the average water content of White Island lavas is 1.4%. A typical phenocryst assemblage of White Island lavas contains 45% clinopyroxene, 40% plagioclase, 10% orthopyroxene and 5% olivine with an average phenocryst mode of 45%. However, the erupted phenocryst assemblages do not represent the true fractionating assemblage and it is inferred that plagioclase was not a dominate fractionating mineral based on a negative correlation between aluminum and magnesium and plagioclase saturation relative to the liquid line of descent.

Subduction zones are a key factor in the geochemical evolution of the continental crust and upper mantle. The conditions during partial melting and crystallisation can provide valuable insights into magma generation and evolution. White Island is an active arc volcano in the Taupo Volcanic Zone (TVZ), New Zealand and provides an excellent environment to assess models of melt generation and evolution within the broader context of arc magmatism. Knowledge of the physical conditions during crystallisation can provide insights into subsequent magmatic evolution. The twopyroxene thermometry of Lindsley (1983) yields crystallisation temperature of 1100°C 1200°C. Using the thermobarometer of Putirka et al. (1996) the crystallisation pressures of the 1977-1992 lavas are 1-8 kbars, equivalent to depths of about 3-25 km. In contrast, the crystallisation pressures for lavas erupted in 2000 are <1 kbar, indicative of very shallow

Keywords: magma generation, crystallisation conditions, White Island, high-Mg andesites E-mail: zmheyl @student.monash.edu

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

A 3D DYNAMIC MODEL OF THE IZU-BONIN-MARIANA SUBUCTION ZONE W. G. M A S 0 N \ D. S t e g m a n ^ L. Moresi^'^ a n d P. G. Betts^ ^ School of Geosciences, Monash University, Clayton, Victoria 3800, Australia ^School of Mathematical Sciences, Monash University, Clayton, Victoria 3800, Australia retarded rollback at that point, while rollback continued along the free end in an arcuate form. Plateaus with a lower density and hence higher positive buoyancy resisted subduction and a detachment appeared in the subducted portion of the slab under the plateau. Plateaus with a smaller positive buoyancy were more likely to subduct and not result in a detachment. Comparison to the slab structure as obtained from seismic tomography reveals some intriguing parallels between the model and the IBM system.

The Izu-Bonin-Mariana (IBM) subduction zone is located in the Northwest Pacific where the Pacific Plate is subducting underneath the Philippine Plate. Several bathymetric highs, including the Ogasawara Plateau just north of the Mariana, impinge upon this oceanic trench, and much speculation has been made as to the effects such highs may have on the evolution of a subduction zone. We constructed a 3D Finite Element model of an oceanic plateau of varying density, impinging on a subduction zone that is rolling back. The plateau pinned the trench and

Keywords: Izu-Bonin-Mariana, Ogasawara Plateau, rollback E-mail: wgmasi @student.monash.edu

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

GEODYNAMIC EVOLUTION, STRATIGRAPHY AND GEOCHEMISTRY OF ATAURO ISLAND, EAST TIMOR M. L. HAWKE School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia

information was available for islands of the Banda Arc. This study provides the first detailed stratigraphic and geochemical study on the island. Atauro consists of a volcanic complex comprising at least three volcanic centres. Geochemical analysis of rocks from the volcanic centres and, where possible, different depths in the volcanic stratigraphy will provide new insights into the extent of magma heterogeneity on the island. It may also be possible to provide some constraints on changes in composition of the source rocks as subduction of the Australian continental crust began and subsequent detachment of the subducted oceanic slab occurred. In order to place results from Atauro in context, this study will also examine the geodynamic formation of Atauro and the Inner Banda Arc Islands. Geochemical trends along the Sunda and Banda arcs will be examined to distinguish the effects of source contamination by continental crust.

The formation of East Timor and the neighbouring volcanic islands of the Banda Arc is the subject of much debate. The Banda Arc consists of a double chain of islands, an 'inner arc' of volcanic origin and an 'outer arc' of an accretionary wedge nature. Atauro Island is situated 30 km north of Timor Island on the extinct Wetar segment of the Inner Banda Arc. Previous work suggests that Atauro formed in a short period of time between 3.5 and 3 Ma and is composed of submarine volcanics. It is suggested that subduction in the region ceased at this time due to collision of the island arc with the Australian continental crust as it progressed northwards and blocked the trench, and that volcanism on Atauro could have accompanied one phase of detachment of the subducted oceanic plate, resulting as a consequence of subduction cessation. Prior to this study, no geological map of Atauro existed and limited stratigraphic

Keywords: Atauro Island, Banda Arc, arc-continent collision, volcanic stratigraphy, geochemistry E-mail: m.hawke@ugrad.unimelb.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

INTRAPLATE HYPERSTHENE-BEARING TRACHYANDESITES: EVIDENCE FOR MULIPLE MAGMA SOURCES IN THE NEWER VOLCANICS PROVINCE, AUSTRALIA Z. HEYWORTH, B. F. Schaefer and 1. A. Nicholls School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

simple fractionation. The McGeorge Hill trachyandesite has a more restricted compositional range for opx of only En52-55. It is also significant that the enclaves do not contain any of the Fe-rich opx found in the northern and western trachyandesites. The northern and western trachyandesites again have a much larger compositional range for cpx (Mg48-60) than the McGeorge Hill trachyandesite (Mg72-75). A basic petrogenetic model inferred for Mt Gisborne involves modification of a transitional to weakly tholeiitic basaltic parent magma through open-system assimilation and fractional crystallisation (AFC) and mixing. The enclaves and Fe-rich opx in the northern trachyandesite are evidence of mixing with a more tholeiitic magma from a differentiated chamber. Subsequent mixing with a highly evolved batch of the more tholeiitic magma produced the Fe-rich opx in the western trachyandesite.

Hypersthene-bearing trachyandesites are relatively rare on a global scale, particularly in basaltic-dominated intraplate settings. The Gisborne complex in Victoria, Australia, contains lavas ranging from highly alkaline basalts to hypersthene-bearing trachyandesites. It comprises up to nine flows, the earliest lavas in the K-rich basanite mugearite range, followed by voluminous more strongly alkaline basalts. Later phases produced at least three major trachyandesite flows, with a final extrusion of transitional basalts. The trachyandesites contain prominent partly resorbed plagioclase, alkali feldspar and quartz crystals as well as plagioclase-hypersthene-augite enclaves. Plagioclase composition in the trachyandesites ranges from An27-58 and shows a general trend of evolution with time. The trachyandesites have an unusually large compositional range for opx from En39-83 indicating complex processes rather than

Keywords: magma mixing, enclaves, Newer Volcanics, AFC processes

E-mail: zmheyl @student.monash.edu

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

DEFINITION AND CLASSIFICATION OF THE ST PETER SUITE STRATIGRAGHY, WESTERN GAWLER CRATON N. C. CHALMERS AND B. F. Schaefer School of Geosciences, Monash University, Clayton, Victoria 3800, Australia emplacement metamorphism. This is further supported by metamorphic amphiboles common within intermediate to mafic dykes. Numerous geochemical similarities are exhibited by the varying lithologies of the St Peters Suite. Similarities such as consistent rare earth element trends displayed by doleritic dykes and cumulate lamprophyres, comparable Ti02, Nb and Y enrichment anomalies between mafic volcanics and the adjacent gabbroic plugs in addition to generally robust trends within the complete St Peter Suite data set indicate a likely single source fractionation controlled evolution with varying emplacement mechanisms determining the range of preserved textures exhibited by the suite. Determining a tectonic setting for the St Peter Suite emplacement is unresolved based on the current data set due to the calc alkaline characteristic suggesting a convergent margin where the bimodal volcanism is inconsistent with a convergent margin.

Characteristics of the tectonic processes that occurred on the Gawler Craton during the Proterozoic represent a vital link in determining the formation of the Australian continent. The St Peters Suite is a Palaeoproterozoic series of calc alkaline magmatic intrusives comprising co-magmatic mafic to felsic lithologies, mafic plugs and cross cutting dykes in addition to minor bimodal volcanics. An intrusive stratigraphy based on cross cutting, truncation and preserved enclave intrusive relationships reveals a transition from dominantly granite emplacement through co-magmatic units to gabbroic plug and doleritic dyke emplacement with related volcanics. Petrological analysis of the St Peters Suite lithologies reveals a strong influence of regional metamorphism which formed the weak to moderate intensity tectonic fabric preserved throughout the suite. Alteration has commonly completely recrystallised the felsic rock forming minerals, particularly the feldspars, indicating a syn- to post-

Keywords: St Peters Suite, Palaeoproterozoic, Gawler Craton, intrusives, stratigraphy

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

PREDICTION OF SLUDGE COMPOSITION AND WATER QUALITY FROM LIME NEUTRALISATION OF ACID ROCK DRAINAGE D. M. MCDONALD and J. A. Webb Department of Environmental Geoscience, La Trobe University, Victoria 3086, Australia

Neutralisation of Acid Rock Drainage (ARD) with lime (Ca(0H)2) produces a metal oxyhydroxide precipitate that may contain a large amount of gypsum. Accurate prediction of whether lime neutralisation sludge from a particular ARD will contain gypsum can be important, as gypsum precipitation may cause extensive scale on treatment equipment, resulting in costly shutdown and cleaning operations; it also increases sludge volumes and decreases the salinity of the treated water. Thus at particular sites gypsum precipitation may or may not be desirable, depending on the relative importance of treated water salinity and sludge bulk. A geochemical model has been developed to predict if gypsum will precipitate during ARD neutralisation using lime. The input data are the concentrations of sulphate and calcium within the ARD, along with the acidity of the ARD (from pH and concentrations of dissolved metals). The model calculates the

lime requirement from the acidity, and adds the resultant calcium input to the initial calcium concentration. It then uses PHREEQC to calculate the activities of sulphate and calcium and the saturation index of gypsum, and so determines whether or not gypsum will precipitate. Plotting the data on a graph of sulphate versus calcium enables direct comparison of the water composition with the gypsum saturation line. The model can also be used to predict the salinity of the treated water and the mass of sludge precipitated. This model was tested using ARD compositions from several Canadian mine sites, one Australian pyrite mine and one synthetic ARD, and the results compared with the mineralogical (XRD) and chemical (XRF) compositions of sludges. The presence or absence of gypsum was accurately predicted in all sites where complete compositional data were available for the ARD.

Keywords: Acid Rock Drainage, Acid Mine Drainage, ARD, AMD, gypsum, precipitation, scale E-mail: d.mcdonald@latrobe.edu.au

Geological Society of Australia Abstracts

Victorian Universities Eartli and Environmental Sciences Conference The University of Melbourne, September 2005

Theme 7

Hydrogeology

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

GROUNDWATER FLOW IN A TERTIARY-QUATERNARY ALLUVIAL SEQUENCE IN THE MOUNT WILLIAM CREEK VALLEY, WESTERN VICTORIA, AND THE POTENTIAL FOR UPWARD LEAKAGE TO INDUCE DRYLAND SALINITY M. D. EDWARDS and J. A. Webb Department of Environmental Geoscience, La Trobe University, Victoria 3086, Australia downward leakage between these two units at the floodplain margins and upper catchment throughout the year, and that potential for upward leakage exists in the lower catchment following the winter peak in recharge. The area where upward leakage from the Tertiary sequence can be invoked as a salinitycausing mechanism is spatially and temporally restricted, but it does correspond to some large areas of land salinisation. The high groundwater pressures causing potential upward leakage can easily be attributed to head gained in the adjacent Grampians ranges. In addition, constrictions in the Tertiary palaeodrainage network, possibly due to neotectonism, affect lateral groundwater flow through the system, and may also contribute to the high groundwater pressures in the Tertiary sequence.

Many low-lying areas of the Mount William Creek valley are affected by dryland salinity due to shallow watertables across the floodplain. The valley contains a sequence of alluvium consisting of a basal gravel and sand unit of Tertiary age, overlain by Quaternary silts and clays. This sequence lies unconformably on a variety of Palaeozoic basement rocks, which outcrop as rolling hills and mountains towards the catchment boundaries. Potentiometric surface maps and bore hydrograph data show that the basal Tertiary sequence and the overlying Quaternary sequence do not act as a single unconfined aquifer. Rather, they present as two aquifers, with the Quaternary silts and clays having some confining capacity over the Tertiary sequence. Hydraulic head difference maps demonstrate that there is potential for

Keywords: Mount William Creek, dryland salinity, head difference. Tertiary palaeodrainage E-mail: Matthew.Edwards@latrobe.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

GEOLOGY AND HYDROGEOLOGY OF A TERTIARY DEEP LEAD PALAEODRAINAGE SYSTEM IN THE GLENELG HOPKINS CATCHMENT, WESTERN VICTORIA M. RAIBER and J. A. Webb Department of Environmental Geoscience, La Trobe University, Victoria 3086, Australia The geology and hydrogeology of an extensive northeast-southwest running Tertiary palaeodrainage system covered by Plio-Pleistocene Newer Volcanic basalts have been characterised using hydrogeological and hydrogeochemical analyses from numerous groundwater observation bores as well as lithological data from exploration and observation bores. The deep-lead system consists of several Pre-Tertiary palaeovalleys which fuse into one central, incised valley; the sediments deposited within the palaeovalley have been assigned to the Palaeocene to Mid Miocene Eastern View Formation. In the centre of the palaeovalley, the Eastern View Formation aquifer consists of more than 140 m of gravel, sand, ligneous clay and coal, deposited in a graben that continuously subsided during deposition of the sediments. Towards the south and southeast, the palaeovalley becomes much shallower and is

directed around a shallow subsurface granite ridge. A head difference map constructed for the Eastern View Formation and the overlying Newer Volcanics suggests that the deep lead is predominantly recharged through eruption points in the northern part of the aquifer, and that there is little or no additional recharge from the overlying basalts towards the south. This is also reflected in the very fresh groundwater in the northern section of the aquifer, due to rapid recharge through the thin, rocky soils, with only limited potential for evapotranspiration to occur. At the southern margin of the Eastern View Formation the groundwater is forced upwards due to the buried granite ridge, which forms a hydraulic barrier. The concentration of salt lakes along the southern margin of the palaeovalley is thought to be an expression of the upwards movement of the groundwater at this location.

Keywords: palaeodrainage system, hydrogeology. Eastern View Formation E-mail: mraiber@students.latrobe.edu.au

Geological Society of Australia Abstracts

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005

Author index M

A Ailleres, L

22, 23, 27

Allen, C. M

Maas, R Martin, S. K Mason, W. G McDonald, D. M McLellan, A Meneghini, B Miller, M. S Mitchell, J. K Moresi, L

B Bassano, K Beardsmore, G. R Betts, P. G Bierlein, F. P Buchanan, L. A C

28 26 42 22, 27 32, 36

Campbell, I. H Chalmers, N. C Chandler, E. B Coffey, J. M Consoli, C. P Corvino, A. F Currie, P. J

10 45 3 16 15, 37 11 37

N Nicholls, I. A

O'Sullivan, R. E

Phillips, G Piper, K.J Plimer, I. R

Ervin, D. B

Raiber, M Ray, D Reid, L Rich, T. H

Gallagher, S.J

16,17

George, R. M

Salisbury, S Schaefer, B. F Seegets-Villiers, D. E Seymon, A Shean, D. A Simmonds, 1 Smith, I. N Stegman, D Stillwell, J. D Sutherland, R

Inglis, M. P

9 25 43 31 28 41, 44 17 27 27

Thorp, N. P

Turner, S. P

V Vickers-Rich, P. A

W Wallace, M. W Webb, J. A Weinberg, R Wijeratne, D. W Willman, C Wilson, C.J. L

L Lewis, D. C

37 41,44, 45 20 27 31, 35 2 2 42 15, 37 37

K Kennet, B. L. N

49 25 4 16, 37

S 30

Harper, K Hassell, T Hawke, M. L Hellstrom, J Hergt, J Heyworth, Z Holdgate, G. R Hough, M Hutchin, S /

10 33 16

F Fitzgerald, E. M. G

£ Edwards, M. D

D Darbyshire, R. 0

28 14, 18 42 46 23 2 40 17 42

17 25, 46, 48, 49 23 26 27 10, 11

Geological Society of Australia Abstracts Wilson, G. J

Victorian Universities Earth and Environmental Sciences Conference The University of Melbourne, September 2005 37

Woodhead, J