Abstract 83 - 20th Victorian Universities Earth & Environmental Sciences Conf Monash Uni 2006

Geological Society of Australia

ABSTRACTS Number

83

20*'' Victorian Universities Earth and Environmental Sciences Conference Monash University 26 October 2006

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

Geological Society of Australia ABSTRACTS

Number 83

VUEESC

2006

OUR LIVING PLANET ITS

IVi

&

RESOURCES

MONASH UNIVERSITY

MONASH University Victorian Universities Eartli & Environmental Sciences Conference: A meeting organised by the students of the School of Geosciences, Monash University 26 October 2006 Editors: Adele Bear, Chris Consoli & Erich Fitzgerald

Geological Society of Australia Abstracts 83

Victorian Eartli and Environmental Sciences Conference Monash University October, 2006

Monash University 26'^ October 2006 Geological Society of Australia Abstracts Number 83 20'^ Victorian Earth and Environmental Sciences Conference Editors: Adele Bear, Chris Consoli & Erich Fitzgerald

ISSN: 0729 01IX ©

Geological Society of Australia Incorporated, 2006

Preferred Citation: Bear, A. N., Consoli, C & Fitzgerald, E. M. G. (editors), 20'^ Victorian Universities Earth and Environmental Sciences Conference, October 2006, Geological Society of Australia Abstracts No 83 Example Citation for papers in this volume Bear, A. N., Cas, R.A.F., Giordano, G, 2006. The eruption dynamics of a large volume phonolitic ignimbrite; implications for caldera collapse - the 151 ka Tufo Rosso a Scorie Nere, Vico Caldera, Central Italy. In Bear, A. N et al. (editors). 20'^ Victorian Universities Earth and Environmental Sciences Conference, October 2006, Geological Society of Australia Abstracts No 83. 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

Victorian Earth and Environmental Sciences Conference IVIonash University October, 2006

Geological Society of Australia Abstracts 83

FORWARD

Hosted at Monash University, this year's VUEESC celebrates the conference's twentieth anniversary. Entitled, 'Our living planet and its resources', it seeks to emphasize the increasing global importance of scientific research in today's world. As communication barriers continue to diminish, and global cooperation increases, sharing information is the sine qua non to preserving our precious planet and its resources. - Lucas Buchanan, Conference Convener

Bacl< row: Sarah IVIartin, Doris Seegets-Villiers, Adele Bear, Chris Consoli, Lucas Buchanan, Wendy Mason, Matt Pankhurst, Benjamin Hagedorn, Minarwan, Megan Hough Front: James Roberts, Chris Folkes, Erich Fitzgerald Absent: Sharon Hall, Jacinta Ogilvie, Rebecca Turnbull, Chiara Lorini

- the 2006 VUEESC organising committee welcomes you! 5

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

PLATINUM SPONSOR

Rio Tinto is one of the world's largest resource companies and a leader in discovering, mining and processing minerals. The Group's worldwide operations supply essential minerals and metals that help to meet global needs and contribute to improvements in living standards. Rio Tinto encourages strong local identities and has a devolved management philosophy, entrusting responsibility with accountability to the workplace. Major products include aluminiuin, copper, diainonds, energy products (coal and uranium), gold, industrial minerals (borax, titanium dioxide, salt, talc and zircon), and iron ore. The Group's activities span the world but are strongly represented in Australia and North America with significant businesses in South America, Asia, Europe and southern Africa. We are one of Australia's largest businesses with 11,000 employees in Australia, and 36,000 employees globally.

Wherever Rio Tinto operates, health and safety is our first priority. We seek to contribute to sustainable development. We work as closely as possible with our host countries and communities, respecting laws and customs. We minimise adverse effects and strive to improve every aspect of our performance. We employ local people at all levels and ensure fair and equitable transfer of benefits and enhancement of opportunities.

Our success as a business depends not only on our skills and the quality and diversity of the Group's assets, but also on our shared commitment to be a dependable global partner and good local neighbour. Graduate Recruitment In 2007 we will be recruiting graduates from a range of Engineering and Science disciplines as well as those studying Business, Commerce & IT. Joining Rio Tinto offers graduates the opportunity to work with people who are leaders in their field and to be a part of a group that develops and manages large, world class, operations. We offer graduates a real job from day one including exciting challenges and opportunities to make a difference through their efforts. Our global operations mean our employees come from many different backgrounds and as graduates develop in their careers there is scope to apply for roles in different countries. This presents opportunities to experience life and friendships in some very unusual places. To find out more about opportunities with Rio Tinto including how to apply, visit www. graduates.riotinto.com 4

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

Benefits Being a part of Rio Tinto, one of the world's leading mining companies, can offer you the opportunity to pursue diverse and fascinating career paths in a number of locations and across a range of commodities. Some of the benefits we offer our graduates include: • Challenging work • Attractive remuneration packages • Monitored development plans • Coaching / Mentoring • The opportunity to participate in Rio Tinto Share Schemes • Training and development to build a successful career, including professional recognitbn • Study assistance for approved development courses • Professbnal fees for recognised Professional Associations • Challenging career opportunities for broader experience within and across business units nationally and potentially internationally Visit our graduate website at: www.graduates.riotinto.com

Rio Tinto is an equal opportunities employer

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

GOLD SPONSORS

ExxonMobil ExxonMobil is a global company with a presence in about 200 countries and territories. ExxonMobil produces more than 4 million oil-equivalent barrels of oil and gas per day and is the world's largest non-governmental marketer of equity natural gas. We are the largest refiner and marketer of petroleum products and the leading manufacturer of lubricating oil basestocks. Our chemical company ranks among the world's largest petrochemical manufacturers. Our Australian activities cover oil and gas exploration and production to petroleum supply, refining and marketing of fuels, lubricants and chemical products. For more information visit our website : www.exxonmobil.com.au

Taking on the world's toughest energy challenges™ GSAV

VICTORIA DIVISION

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

ASEG

Australian Society of

Exploration Geophysicists SILVER SPONSORS

PESA PESA strives to provide and foster the advancement of technological, professional and scientific aspects of petroleum exploration, development and production. The society actively supports school education programs aimed at raising public awareness of the geoscience behind oil and gas occurrences. By habitually sponsoring local university conferences the society wishes to encourage students to join PESA and consider a career in the petroleum industry. Society members have access to a wide range of special programs; facilities and functions. The Vic/TasBranch's Student Chapter regularly conducts field trips (including visits to drilling operations whenever possible) and petroleum geological workshops that are free of charge. The Society holds monthly lunchtime meetings in Melbourne's CBD during which industry professionals and research students present new results from ongoing work programs.

Petroleum Exploration Society of Australia Ltd Victoria/Tasmania Branch DPI Geoscience Victoria

GeoSdence Victoria IVictoria The Place To Be pmd * ORG

pmd*CRC

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

PGN

iPGN

Post Graduate Niche geoscience

pgn@skilledgeoscience.com mobile 0402 215 368

AoDiTioNAL SPONSORS GeoVisio

"linking industry and students"

CADBURY BLUNDSTONE MUSEUM VICTORIA This conference was supported by the iVIonash Research Graduate School's Postgraduate Conference Organiser's Grant and IVIonash University Faculty of Science

A great big Thankyou to all our Sponsors!! - 2006 VUEESC Committee W

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

Contents

SESSION ONE: GEOCHEMISTRY AND CRUSTAL PROCESSES F. KOHLMANN, A. J. W. Gleadow, B. P. Kohn and 0. I. Pakes Atomic force microscopy study of fission tracks in apatite and muscovite M. RAVEGGI, D. Giles, J. Foden, M. Raetz and I. Nicholls The role of magmatic and exhalative rocf<s in the brol<en hill systems: geochemical and isotopic evidence 0. H. WOOF New evidence for the possible extension of northwestern Tasmania into southern Victoria K. M. DUDGEON and R.A.F. Gas The volcanology of diamondiferous lamproites: comparisons of the Miocene intravent Ellendale 9 and extravent 81 mile vent deposits, Ellendale, west Kimberley region, western Australia K. 8. ELY Geological mapping ofAtauro island, east Timor: the early stages of arccontinent collision

SESSION TWO: ENVIRONMENTAL SCIENCE M. MCBAIN Alpine mossbeds: popular myth or unpopular reality? K. SAUNDERS and A. McMinn Recent environmental changes and human impact on the Gippsland lakes, Victoria V. R. TAMMIREDDY and J. E. Reid Use of geophysical methods to identify seepage flow from a mine tailings dam, zinifex, western Tasmania T. TUTT, J. Sherwood and B. Knight Bioremediation of an acidic mine lake at Wensleydale, Victoria Z. ZHANG g

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

A framework for modelling landscape dynamics and their impact on cool temperate rainforest in the Strzelecki ranges, Victoria S.A. WOOD and J. BERINGER Impacts of forest age on water use in mountain ash forests

SESSION THREE: ECONOMIC GEOLOGY M.HOUGH, F. P. Bierlein and L. Ailleres Dyke controls on gold mineralization: Cohen's reef, Walhalla, SE Australia T. P. TRIANTAFILLOU, G. R. Beardsmore and L. Ailleres 3D geothermal modelling - how does heat transfer through stratigraphy and discontinuities in a sedimentary basin? M. VAN DONGEN, R. F. Weinberg and A. G. Tomkins Laser ablation ICP-MS of melt inclusions in the Northparkes porphyry copper deposit

SESSION FOUR: HYDROGEOLOGY AND CLIMATOLOGY M. RAIBERand J.A.Webb A multi-scale isotopic tracer study to delineate aquifer interactions and their impact on groundwater salinisation in the eastern Hopkins catchment, Victoria, Australia K. M. BAILUEandJ.A. Webb Groundwater Recharge And Movement on a Small (paddock) Scale, Willaura area, Western Victoria B. HAGEDORN and I. Cartwright Major ion chemistry of rivers draining the Victorian alps (Australia): constraints on chemical weathering and its dependence on lithologic, climatic and anthropogenic influences B. MENEGHINI and I. Simmonds An analysis of the annular mode influence on hydrological cycle variability using the 'nudging' approach S.K. HAGERTY and J. A. Webb The effect of groundwater input on stream salinity of the upper Loddon catchment, central Victoria TO

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Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

SESSION FIVE: PALAEOBIOLOGY 8. K. MARTIN Butterfly nets and pitfall traps: niche biased preservation in middle and late Triassic insect faunas of Australia L. BUCHANAN Australia's early crocodiles: ecological mechanisms of evolution D.A. SHEAN Palaeoecological significance of the Pleistocene fossil deposits of the Buchan caves, southeast Australia E. M. G. FITZGERALD, T J. Senden, R. E. Fordyce, S. J. Gallagher, J. A. Long and T. H. Rich Evolution of hearing in baleen whales revealed by high resolution computed tomography of the inner ear of toothed mysticetes (mammalia: cetacea) K. CHARLTON Late Neogene climate change and genetic divergence amongst southern Australian bottlenose dolphins (odontoceti: delphinidae: tursiops sp.) C. CONSOLI, J.D. Stilwell and R Vickers-Rich The Takatika grit, Chatham Islands: inferred high-productivity in a southern high latitude, late cretaceous marine ecosystem B. CHOC Ray-fins of the gogo: exceptional Devonian fossils shed light on the early evolution of actinopterygian fish (osteichthyes) M. R INGLIS A fishy problem: relationship issues among archaic fish (osteichthyes: actinopterygii) and the role of Victorian relict taxa in resolving the conflict S. K. MARTIN Waterbugs (hemiptera: heteroptera) from the lower cretaceous Koonwarra fossil bed, Gippsland basin, Victoria D.E. SEEGETS-VILLIERS Evidence of multi-source provenance for early cretaceous sediments in the Gippsland basin D. A. SHEAN A case of mistaken identity: changes in the artistic restorations of the Pleistocene marsupial palorchetes azael

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

SESSION SIX: GEODYNAMICS, TECTONICS AND BASIN EVOLUTION W. G. MASON, L. Moresi and P. G. Betts Bathymetric highs at subduction zones A. MCLELLAN, L. Ailleres and R. Weinberg Geometry of geology at broken hill, NSW, Australia: testing previous models using three-dimensional models and geophysical techniques MINARWAN, M. Hall and R. Gas Variation of syn-rift stratigraphy in the Woolsthorpe-Cobden area, central Otway basin, Victoria, Australia - evidence from seismic and well data M. PANKHURST Geodynamics of the Gawler range volcanics, south Australia: physiochemical and tectonic constraints on a felsic large igneous province A. N. BEAR, R. A. F. Gas and G. Giordano The eruption dynamics of a large volume phonolitic ignimbrite and its implications for caldera collapse L. BRETT, M. Raetz and L. Ailleres 3D geology of the Tarcoola basin, Gawler Craton, south Australia N. J. PHILLIPS and R G. Betts Geophysical mapping of the Hutchison group beneath the Gawler range volcanics, Gawler Craton, Australia

GSAV EVENING PLENARY SESSION G. GIBSON Mining and Reservoir Trigge Events /\j

and Anticipation of Future

'Lx^ W. PECK

^^ ,

Research into Seismic Activit^r Hill Mine

els of the Pasminco Broken

VICTORIA DIVISION TT

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

PROGRAMME 9.00 a.m

Introductory Remarks

9.15

Keynote Address SESSION ONE: GEOCHEMISTRY AND CRUSTAL PROCESSES

9.30 - 9.45

9.45-10.00

10.00-10.15

10.15-10.30

Kohlmann et al.

Raveaai et al.

Woof

Dudaeon & Cas

"Posters viewed concurren :ly " "

10.30

MORNING TEA

SESSION TWO: ENVIRONMENTAL SCIENCE 11.00-11.15

11.15-11.30

11.30 -11.45

11.45-12.00

12.00-12.15

Saunders & McMinn " Posters viewed concurrently

Tammireddy & Reid

Tutt et al.

Zhang

McBain

12.30

LUNCH

SESSION THREE: ECONOMIC GEOLOGY

1.15-1.30

1.30-1.45

1.45-2.00

Houah et al. "Posters viewed concurrentiv

Triantaflllou et al.

Van Donaen et al.

SESSION FOUR: HYDROGEOLOGY AND CLIMATOLOGY

2.15-2.30

2.30 - 2.45

2.45 - 3.00

3.00-3.15

Raiber & Webb

Baliue & Webb

Hagedorn & Cartwriaht

Meneghini & Simmonds T3

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

3.15

AFTERNOON TEA

SESSION FIVE: PALAEOBIOLOGY

3.30 - 3.45

3.45-4.00

4.00-4.15

4.15-4.30

4.30-4.45

Martin

Buchanan

Shean & Fitzgerald

Fitzgerald et al.

Charlton

SESSION SIX: GEODYNAMICS, TECTONICS AND BASIN EVOLUTION

4.45 - 5.00

5.00-5.15

5.15-5.30

5.30 - 5.45

Mason

McLellan

MInarwan

Pankhurst

Pnstfirs viewed cnnnurrently

5.45

Concluding Remarks

6.00

End of conference drinks, finger food & Awards Presentation

6.30

GEOLOGICAL SOCIETY OF VICTORIA EVENING PLENARYSESSION Gary Gibson Mining and Reservoir Triggered Earthquakes, and Anticipation of Future Events Warren Peck Research into Seismic Activity in the Deeper Levels of the Pasminco Brol<en Hill Mine

W

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

GROUNDWATER RECHARGE AND MOVEMENT ON A SMALL (PADDOCK) SCALE, WILLAURA AREA, WESTERN VICTORIA K. M. BAILUE and J. A. Webb Department of Environmental Geoscience, La Trobe University, Victoria 3086, Australia

Very few studies have investigated how groundwater recharge, movement and discharge occur on a small scale. This project examines an instrumented 400x800 m paddock in the Willaura area in Western Victoria; twelve recording piezometers measure groundwater level fluctuations eight times a day. The aims of this project are to determine how infiltration varies according to changes in land use (fallow to cropping) and smallscale differences in soil characteristics, as well as the effect on groundwater level of rainfall events (direct recharge and increase in soil moisture) and lateral groundwater flow. The site lies in Quaternary alluvium overlying Palaeozoic basement (sandstones and shales). The surface layer of the soil profile contains ferruginous gravel, washed downhill from the edge of the nearby basalt plain. Underlying this is a heavy yellow mottled clay with sandy loam layers. Soil moisture reaches 15% in the top 10cm of soil and increases down profile to -20%. Soil salinity varies substantially both down the profile and across the site. The watertable at the site lies close to the surface (2 - 5m). The detailed hydrograph data collected so far shows minor fluctuations due to variations in barometric pressure; these can be identified using the air pressure record from a nearby weather station.

The groundwater pressure in the piezometers shows more significant increases within two days of a small rainfall event (<10mm), indicating either very rapid infiltration or (more likely) an increase in groundwater pressure due to the weight of water in the overlying soil. Recovery of the groundwater pressure is also very rapid (within a day). However, three of the piezometers respond to rainfall events much more slowly. These short-term fluctuations were superimposed on a longer-term fall in groundwater pressure from May to mid July of 30cm, recorded by all piezometers. This probably represents lateral groundwater flow towards the Hopkins River to the west, coupled with an overall lack of recharge reflecting the low rainfall in the previous months. However, rainfall of 22mm over two days in mid July stabilized the groundwater pressure in nine of the piezometers, indicating that significant recharge followed this event. Groundwater pressures in the other three piezometers increased rapidly by as much as 25cm, suggesting that these three sites, which are located in a restricted part of the paddock, may be recharged differently. The soil in this part of the paddock is thicker, more saline and less permeable; the rise in groundwater pressures may reflect the increasing weight of the thick clay layer following the rainfall event.

Keywords: groundwater recharge, piezometers, infiltration. Email: k_bailue@hotmail.com

T5

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

THE ERUPTION DYNAMICS OF A LARGE VOLUME PHONOLITIC IGNIMBRITE AND ITS IMPLICATIONS FOR CALDERA COLLAPSE A . N. B E A R \ R. A . R Cas^ a n d G. G i o r d a n o ^

^ School of Geosciences, Monash University, Victoria 3800, Australia 2 Departimento di Scienze Geologiche, Universita di Roma Tre, Rome, Italy, 00146

The current understanding of the eruption dynamics, caldera collapse and transportation processes of pyroclastic flows and their deposits have derived primarily from high silica, felsic composition, examples. Comparatively little is known about calderas and their associated pyroclastic flows comprised of undersaturated, alkali-rich, silica deposits such as phonolitic composition ignimbrites. The 151 ka Tufo rosso a scorie nere' ofVico Caldera, Central Italy, a large volume (5.3 km^) intermediate composition ignimbrite, will be used as a case study, to understand the key factors that influence explosive eruptions of this kind. The principal facies of the Tufo Rosso' include a basal fallout deposit, a number of proximal lag breccias and both small and large volume ignimbrites, all of which are indicative of a major caldera - forming 'explosive' eruptive origin. A preliminary model for the evolution of caldera collapse based on detailed reconstruction of the stratigraphy is presented here: Phase 1 - Initial Plinian column formation: Phase 2 - Partial plinian column collapse: Phase 3 - Contemporaneous (?) fire fountaining / plinian column collapse in the north & vent widening in the south: Phase 4 - Final caldera collapse.

Keywords: caldera, phonolitic, ignimbrite, proximal lag breccia, plinian, fire fountaining

Email: Adele.Bear@sci.monash.edu.au

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Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

3D GEOLOGY OF THE TARCOOLA BASIN, GAWLER CRATON, SOUTH AUSTRALIA L. BRETT, M. Raetz and L. Ailleres School of Geosciences, Monash University, Victoria 3800, Australia

The Tarcoola Basin is located within the central western Gawler Craton, where Archaean/Early Proterozoic Wilgena Hill Jaspilite iron formation and Paxton Granite form the basement to the Palaeoproterozic Tarcoola Formation. The fluvial to marine cover sequence is preserved within an elongate east-west basin remnant of unknown original architecture. The Archaean basement has been extensively deformed, whereas the Palaeoproterozoic cover sediments of the basin have been weakly to moderately deformed, which is indicated by open upright folding, inferred thrusting and block faulting. The regional metamorphic grade is lower greenschist fades. Silcrete capped mesas of Late Jurassic Algebuckina Formation and a drape of Cenozoic colluvial, alluvial and aeolian sediments covers much of the area leaving limited outcrop, which has caused this region to remain poorly understood. High quality magnetic and gravity surveys were flown over the basin in March 2004, which together provide an exceptional opportunity for potential field interpretation and subsequent modelling. We present an interpretation of the potential field data constrained by field observations to assess the geometry and significance of the ~1655Ma Tarcoola Basin and how it relates to the underlying basement and associated 1590-1575Ma Hiltaba suite intrusions. The methodology involves drawing geological cross-sections that are consequently tested against both gravity data and magnetics. The sections are built into a 3D model of the basin, basement and intrusion interfaces. The geological constraints consist of field observations in outcrop and drill core. Petrophysical properties (density and magnetic susceptibility) were also collected on drill core samples and used as input into geophysical modelling. The resulting model shows that the preserved Tarcoola Basin has the appearance of a horst and graben geometry, but also must account for missing strata on what could be inferred horst blocks. Two possible scenarios may account for the present basin architecture and missing stratigraphy: (1) a Horst and Graben Model in which the missing strata was simply never deposited and (2) a more complex Tectonic Excision scenario with several Models possible.

Keywords: Gawler Craton, Tarcoola basin, structure, potential field, 3D modelling. Email: lbre5@students.monash.edu.au

17

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

AUSTRALIA'S EARLY CROCODILES: ECOLOGICAL MECHANISMS OF EVOLUTION L. BUCHANAN School of Geosciences, Monash University, Victoria 3800, Australia

Australia's Cenozoic crocodilians explored an assorted range of morphologies that rivals that of any other continent for this time. A group of apparently endemic crocodiles, the Mekosuchinae, dominated numerous ecologic niches throughout the continent, developing a broad and diverse range of morphologies. Ecomorphs such as deep-snouted terrestrial ziphodonts, short- and broad-snouted terrestrial and possibly arboreal forms, as well as large, robust, generalised forms, dominated Australia's mid to late Cenozoic herpetofaunas. However, as well understood and documented as this radiation is, its origins have only recently begun to take shape. New material recovered from the Eocene Rundle Formation of The Narrows Graben (eastern-central Queensland) has revealed a new species of early mekosuchine, the fourth in the genus Kambara. The recovery of abundant material has allowed for a more in-depth analysis of mekosuchine origins. The relevance of this new assemblage lies not only in its age and abundance of material, but also in the different morphology of the specimens therein. Studies have discerned crucial variations between this new assemblage and other closely related assemblages. These variations, many of which relate to jaw function and bite morphology, when considered in ecologic context, provide a unique perspective into the evolutionary mechanisms that drove their speciation. In broader relevance, these evolutionary mechanisms provide valuable insight into the nature and origins of later Cenozoic diversity. The specific slice of time captured in the Rundle Formation deposit clarifies not only the early mekosuchine origins, but also the potential drivers and controls of mekosuchine evolution. Palaeoecological reconstructions based upon microspore content and sedimentology show that The Narrows Graben witnessed numerous periods of sedimentary and environmental cycles. Other studies (isopach thickness and Bouguer gravity anomalies) have revealed that the basin is broken up into two major depocentres by a topographic high: the shallower Rundle deposit in the north and the deeper Stuart deposit in the south. Periods of low water levels would have split the basin into disparate ecologic systems, which, in turn, provided for the opening of new niche opportunities. It is this cyclic nature of The Narrows Graben basin that, when considered in the light of the Pulse-Turnover Hypothesis, is thought to have been the requisite driver for early mekosuchine speciation and possibly for further macroevolution.

Keywords: Mekosuchinae, Kambara, Crocodylia, Rundle Formation, Eocene, Cenozoic, Australia evolution, palaeoecology

Email: lucas.buchanan@sci.monash.edu.au

18

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Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

SALINE INTRUSION IN AN UNCONFINED AQUIFER, OTWAY BASIN, SOUTHEAST AUSTRALIA A. L. BUSH and C. R. Lawrence School of Earth Sciences, University of Melbourne, Victoria 3010, Australia

The Gambier Limestone and the Port Campbell Limestone of the coastal Otway Basin, South Australia and Victoria, form the unconfined to semi-confined late Cenozoic Limestone Aquifer. This carbonate aquifer is a major water source for agriculture, domestic and town supplies. Extraction causes perturbations that distort an otherwise seaward sloping watertable. Drawdown due to extraction has long been linked to a risk of saline intrusion in coastal areas. In the late 1960s, when groundwater irrigation and urban supplies intensified, parts of the aquifer experienced up to 15 m drawdown near rural centres such as Port Campbell, Portland and Mt Gambier. In some cases, drawdown resulted in the watertable reaching sea level, reversing the hydraulic gradient, however no saline intrusion had been documented until 2002. Currently, south of Mt Gambier, two sites within 1000 m of the coastline yield groundwater with an electrical conductivity exceeding 45000 pS/cm, overlain by much fresher groundwater (2000 (jS/cm), indicating seawater intrusion. At one of these sites, the saline-fresh water interface lies below 124 m. The saline intrusion has targeted the most porous Member of the Gambier Limestone, the Camelback Member, a highly fractured and karstic horizon preferentially tapped for irrigation supply. The Ghyben-Herzberg Solution has been used to calculate three possible solutions for a sharp salinefresh water interface; one for pre-development watertable and sea levels, a second for current watertable and sea levels, and a third for pre-development watertable levels and sea levels appropriate for the last glacial maximum (at about 21 Ka). The results show that, although a sea level rise of around 140 m since the last glacial maximum would be responsible for a rise in the interface in the order of thousands of metres, the sea level change in the last 100 years is insignificant. In contrast, watertable drawdown of up to 15 m in the same timeframe has the potential to raise the interface by 100-300 m. To add complexity, there is a large discrepancy between the observed interface depth south of Mt Gambier, and the calculated depth. Given the current watertable and sea levels at that site, the interface is more than 100 m deeper than expected. This discrepancy demonstrates the lag time in the aquifer response to the recent drawdown in the last five decades. Hence, the saline-fresh water interface is expected to rise further in the near future regardless of further drawdown.

Keywords: Otway Basin, unconfined aquifer, saline intrusion, lag response

Email: a.bush@pgrad.unimelb.edu.au

Tg

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

LATE NEOGENE CLIMATE CHANGE AND GENETIC DIVERGENCE AMONGST SOUTHERN AUSTRALIAN BOTTLENOSE DOLPHINS (ODONTOCETI: DELPHINIDAE: TURSIOPS SR.) K. CHARLTON^ ^ School of Biological Sciences, Monash University, Victoria 3800, Australia 2 Australian Centre for Biodiversity: Analysis, Policy and Management, School of Biological Sciences, Monash University, Victoria 3800, Australia 3 Centre for Environmental Stress and Adaptation Research (CESAR) School of Biological Sciences, Monash University, Victoria 3800, Australia

Bottlenose dolphins (Tursiops sp.) have a global distribution throughout tropical and temperate waters, both inshore and offshore, and exhibit regional morphological and genetic variation. Current genetic data strongly suggest that the 'inshore' southern Australian bottlenose dolphin {Tursiops sp.) is unique, long isolated and possibly locally adapted. The level of divergence (5.5%) observed between the 'inshore' dolphin and its nearest known relative, T. truncatus found in offshore waters, strongly suggests that this unique 'inshore' dolphin represents a new sub/species that is restricted to southern Australian waters. How might such a divergent group have arisen? The rate of mitochondrial DNA (mtDNA) control region divergence in cetaceans has been estimated at between 0.5-1 % per million years, placing the time of species split from the earliest known relative, at 2.75-5.5 million years ago. The Family Delphinidae has a fossil record beginning in the Late Miocene, about 11 Ma, followed by rapid radiation making taxonomic classification of a number of living species complexes particularly difficult, including the Tursiops-Delphinus-Stenella complex. The extant genus, Tursiops, has Early Pliocene records worldwide, with the earliest Australian Tursiops fossW being from western Victoria (Portland) and dating between 2.5 and 4.5 Ma (Pliocene). Periods of global warming within the Pliocene through Pleistocene epochs may have created habitat, via sea level change, for radiating dolphin species. By investigating average sea level and temperature changes throughout the late Cenozoic era we can hypothesize where and how the unique southeast Australian population may have arisen. The Gippsland and Bass Basins are of significant interest as possible niches during warmer Pliocene periods for the establishment of coastal founder populations. The current resident dolphin population(s) in coastal Victoria (Port Phillip Bay and Gippsland Lakes) must have established relatively recently with the release of suitable habitat during the more recent postglacial period. The extensive genetic divergence and the long-term isolation that this implies raises the possibility that southern Australian 'inshore' bottlenose dolphin may represent a new, possibly locally adapted sub/species. If this proves to be the case they arguably constitute a distinct entity worthy of separate conservation management.

Keywords: Tursiops, Cetacea, Odontoceti, Delphinidae, mitochondrial DNA, divergence, evolution, Australia, Pliocene

Email: kate.charlton@sci.monash.edu.au

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

RAY-FINS OF THE GOGO: EXCEPTIONAL DEVONIAN FOSSILS SHED LIGHT ON THE EARLY EVOLUTION OF ACTINOPTERYGIAN FISH (OSTEICHTHYES) B. CHOO^ 2

^ Department of Earth and Marine Sciences, Australian National University, Canberra, ACT 0200, Australia 2 Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia

Actinopterygians or ray-finned fish are today the most diverse group of fishes but many details of their early evolution remain unclear, particularly with regards to the interrelationships of stem-group taxa. Many early forms are imperfectly known due to limitations of preservation. Specimens are usually represented either as flattened skeletons with little or no preservation of delicate internal features, or as disarticulated threedimensionally preserved elements. Spectacular exceptions are to be found in the famous Late Devonian (lower Frasnian) Gogo fish fauna of Western Australia that displays an extraordinary level of fossil preservation within calcareous concretions. These nodules are prepared with a weak acetic acid solution, dissolving the surrounding matrix to expose vertebrate remains. Fossil fish are often recovered as entire individuals with full dermal and perichondral preservation in three-dimensions. These include the only Devonian actinopterygians in the world to combine finely preserved neurocranial detail with the remainder of the skull and associated postcrania in articulation, enabling accurate anatomical reconstruction. While considerably less diverse than contemporaneous placoderms and sarcopterygians, basal actinopterygians are a common element of the Gogo fauna with multiple individuals known for at least three taxa. "Mimia" toombsi (currently preoccupied) and Moythomasia durgaringa generated a great deal of interest in basal Actinopterygii when these forms were described in detail in 1984. Both have featured in all subsequent phyletic studies of early actinopterygians despite the fact that key features of the latter have never been fully documented. A third, as yet undescribed taxon is currently being examined which differs from the other two forms in features of the skull, body form and squamation. Preliminary studies suggest that it may possess the most primitive braincase within clade Actinoptera. An expedition to the Gogo Formation in July 2005 recovered a wealth of new material including at least 14 complete or partial actinopterygians representing all three taxa. Currently undergoing preparation, this material from will allow for a complete description of the new taxon as well as a thorough redescription of "Mimia" and Moythomasia, with preliminary observations suggesting inconsistencies with previously published reconstructions. Connected coding into previously published character matrices should provide a better understanding of the phylogenetic relationships within this clade.

Keywords: Vertebrate palaeontology, fossils, Gogo Formation, Devonian, Western Australia, Actinopterygii, fish

Email: bchoo@museum.vic.gov.au ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^

i

n

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

THE TAKATIKAGRIT, CHATHAM ISLANDS: INFERRED HIGHPRODUCTIVITY IN A SOUTHERN HIGH LATITUDE, LATE CRETACEOUS MARINE ECOSYSTEM C. CONSOLI, J.D. Stilwell and P. Vickers-Rich School of Geosciences, Monash University, Victoria 3800, Australia

The fossil record of the Takatika Grit preserves an excellent example of a Late Cretaceous ecosystem in the Southern Hemisphere. The Cretaceous-Paleogene glauconitic sandstone is exposed along the northern coast of Chatham Island, located 860 km east of South Island, New Zealand. The majority of fossils comprise marine reptile remains, as well as sharks, fish, molluscs and sponges, but some fossils represent terrestrial fauna (avian and non-avian theropod dinosaurs) and flora (conifers) washed into the shallow marine succession. It is now known that mosasaurine mosasaurs and elasmosaurid plesiosaurs existed within the Chathams region and are represented by associated and articulated axial and limb elements. They co-existed with other pelagic taxa including lamniform and hexanchiform sharks (e.g. Chlamydoselachus), as well as the chimaeroid Edaphodon. Molluscan fauna includes Pachydiscus ammonites and nautiloids, as well as gastropods and bivalves. The first record of well-preserved hexactinellid sponge body fossils is preserved in abundance and in great diversity. The Takatika Grit sequence represents the initial encroachment of the South Pacific Ocean over the landmass known as Chatham Peninsula, the eastern extension of Zealandia (New Zealand, Campbell Plateau, New Caledonia and Chatham Rise). It is emerging that this region was a zone of high-productivity, which was perhaps induced by upwelling inferred from the palaeogeographical configuration of Zealandia and corresponding palaeocurrent data. Moreover, sedimentological indicators, including the presence of abundant phosphorite nodules and an excess of biogenic silica, corroborate the model of nutrient-rich upwelling waters. This may account for the high diversity of marine vertebrates and invertebrates in the Takatika Grit that incorporated several pelagic apex predators and diverse benthic taxa. Observations within the Takatika Grit could have implications for the palaeoecology and biodiversity of coeval fossiliferous deposits worldwide.

Keywords: palaeontology, palaeoecology, marine reptiles, Chondrichthyes, upwelling. New Zealand, Late Cretaceous

Email: chris.consoli@sci.monash.edu.au 22

^ ^ ^

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

THE VOLCANOLOGY OF DIAMONDIFEROUS LAMPROITES: COMPARISONS OF THE MIOCENE INTRAVENT ELLENDALE 9 AND EXTRAVENT 81 MILE VENT DEPOSITS, ELLENDALE, WEST KIMBERLEY REGION, WESTERN AUSTRALIA K. M. DUDGEON and R.A.F. Cas School of Geosciences, Monash University, Victoria 3800, Australia

Lamproites are ultramafic alkaline volcanic rocks originating as low viscosity magmas that often transport diamonds to surface levels. Many aspects of these volcanic rocks, including their physical eruption and emplacement processes, remain unclear and poorly understood. More comprehensive mapping and detailed fades analysis of these diamond-bearing rocks is needed to produce accurate histories and reconstructions of eruptive and depositional processes. The Miocene Ellendale Lamproite field is located in the West Kimberley Region of Western Australia. Ellendale 9 (E9) and 81 Mile Vent are two pipes found in the central area. E9 is currently the focus of a diamond mining operation. This study will compare the intravent deposits of E9 and the intravent and extravent deposits of 81 Mile Vent to reconstruct the eruptive history and processes of E9. Quartzose volcaniclastics are confined to the south end of the West Pit of E9. Current data suggests their formation by early phreatomagmatic volcanism through country rock. Quartz poor volcaniclastic deposits occur in most of the West Pit and the margins of the East Pit and appear to have originated by similar processes after initial country rock and later volcaniclastic excavation. Variations in alteration processes and intensity produce colour changes across the pit. E9 contains olivine-rich porphyritic coherent lamproite. Olivine has been altered to serpentine and much of the fades has been altered to clay, with dominant carbonate veining. Preliminary results suggest progressive explosive volcanism from west to east in E9, followed by later intrusion of coherent lamproite in a fissure-style eruption system in the east. This resulted in large volumes of coherent lamproite including sills and dykes intruding the previously deposited volcaniclastics. Late-stage confined lava lakes in the east, and possibly west, coincided with a late stage of non-explosive volcanism. The volcaniclastic fades of E9 are severely altered, as are those at 81 Mile Vent. They are generally massive and lack structures, however several subfacies exhibit excellent subhorizontal bedding, suggesting pyroclastic flow and/or surge depositional mechanisms. The 81 Mile Vent volcaniclastics illustrate debris flow and pyroclastic flow and surge deposit characteristics, with well preserved cross laminations and bedding. The coherent leucite-phlogopite lamproite fades at 81 Mile Vent is the dominant pipe infill. It can be subdivided into several subfacies that vary in their texture and crystal content.

Keywords: Ellendale, lamproite, pyroclastics, lava lakes, alteration, volcanology

Email: kmdudi@student.monash.edu.au

23

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

GEOLOGICAL MAPPING OF ATAURO ISLAND, EAST TIMOR: THE EARLY STAGES OF ARC-CONTINENT COLLISION K. S. ELY School of Earth Sciences, University of Melbourne, Victoria 3010, Australia

The Sunda-Banda arc system comprises a 4000 km-long chain of active volcanic islands, extending from central Sumatra in the east to Banda Island in the west. The Pliocene collision of the northern margin of the Australian continent with the Banda Arc north of Timor has been linked to the cessation of volcanism in the region, and subsequent rapid uplift. This relationship raises questions regarding the fate of the descending slab, and what the surface expression of the arc reveals about final subduction processes. The Timor region of the Banda Arc provides the rare opportunity to investigate the early stages of arc-continent collision. Understanding the magmatic and tectonic response to the early stages of collision is key to recognition of these events in older orogens. The island of Atauro is located in the centre of the volcanically inactive part of the arc, which at 400 km long is the longest extinct segment of the entire Sunda-Banda system. Prior to this study, published Atauro data included only limited geochemistry and geochronology; no geological maps or details of the island's volcanic stratigraphy were available. Mapping of the volcanic basement of Atauro established a stratigraphy comprising three major units, locally intruded by dykes and sills of varied composition. Brecciated dacitic lavas occur widely across the island, along with thick sedimentary deposits of similar composition. A distinctive clinopyroxene-phyric basalt occurs only in the southwest part of the island. The distribution of this unit, along with the geomorphology of this area, clearly defines a volcanic centre. Erosion and possible large scale gravitational collapse have resulted in the location of other volcanic centres ambiguous. Limestone coral reef terraces, mapped at up to 700 m above sea level, mantle much of the island. This distribution demonstrates both the submarine nature of the volcanism and the ongoing rapid uplift that has occurred since the end of volcanism around 3 Ma. The extinct segment of the Banda Arc in which Atauro is located has a strong spatial association with an underlying aseismic zone evident from the earthquake record of the region. It is suggested that the aseismic zone is a result of the tearing of the down going slab subsequent to the onset of collision. The rapid uplift of Atauro and neighbouring islands is an isostatic response to slab tear, representing a reduction in the transfer of stress from the descending slab to the surface.

Keywords: Banda volcanic arc. East Timor, arc-continent collision, slab dynamics

Email: k.ely@pgrad.unimelb.edu.au

2T

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

EVOLUTION OF HEARING IN BALEEN WHALES REVEALED BY HIGH RESOLUTION COMPUTED TOMOGRAPHY OF THE INNER EAR OF TOOTHED MYSTICETES (MAMMALIA: CETACEA) E. M. G. F I T Z G E R A L D ^ a n d T. H. Rlch^

T. J . S e n d e n ^ R. E. F o r d y c e ^ S. J . G a l l a g h e r ^ J . A . L o n g ^

^ School of Geosciences, Monash University, Victoria 3800, Australia 2 Museum Victoria, G.RO. Box 666, Melbourne, Victoria 3001, Australia ^ Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia ^ Department of Geology, University of Otago, RO. Box 56, Dunedin, New Zealand ^ School of Earth Sciences, University of Melbourne, Victoria 3010, Australia

All living cetaceans (whales and dolphins) belong in either one of two distinct clades with contrasting specializations for underwater hearing: the toothed echolocating Odontoceti (hear and produce ultrasonic sounds), and the baleen-bearing, filter-feeding, Mysticeti (hear and produce infrasonic signals). Together, the Odontoceti + Mysticeti form the crown group Cetacea, or Neoceti. Outgroup comparison between Neoceti and stem cetaceans (Archaeoceti) suggests that ultrasonic, and infrasonic, hearing are synapomorphies of Odontoceti and Mysticeti, respectively, and evolved concurrently with the divergence of these clades. Although the earliest odontocetes were probably capable of both ultrasonic hearing and echolocation, the nature of hearing in basal mysticetes has remained unknown. Here we present the first data on inner ear morphology and inferred hearing ability in a basal toothed archaic mysticete {Mammalodon colliveri, Late Oligocene, Australia). High-resolution computed tomography (CT) scans of the periotic bone show a cochlear morphology consistent with ultrasonic hearing, although we have not identified structures elsewhere on the skull that might have functioned to produce ultrasonics. If acoustic-related structures are plotted on a stratigraphically-calibrated phylogeny of Cetacea, the pattern suggests that ultrasonic hearing was present in the common ancestor of odontocetes and mysticetes. Ultrasonic hearing was later lost, with shift to infrasonic hearing as toothless baleen-assisted feeding evolved in the Chaeomysticeti. The shift to infrasonic hearing is linked with character complexes related to bulk filterfeeding, and could reflect such social-ecological factors as long-distance communication during migration to and time at polar feeding grounds.

Keywords: Cetacea, Mysticeti, Mammalodon, Oligocene, periotic, cochlea, ear, hearing, evolution

Email: efitzger@museum.vic.gov.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

MAJOR ION CHEMISTRY OF RIVERS DRAINING THE VICTORIAN ALPS (AUSTRALIA): CONSTRAINTS ON CHEMICAL WEATHERING AND ITS DEPENDENCE ON LITHOLOGIC, CLIMATIC AND ANTHROPOGENIC INFLUENCES B. HAGEDORN and I. Cartwright

School of Geosciences, Monash University, Victoria 3800, Australia

To understand the coupling between landscape evolution and chemical weathering within a single orogenic belt, fresh surface water samples from a network of 15 rivers draining the Australian Victorian Alps (SE-Australia) were sampled during low flow regimes (winter 2006) and analysed for major ions, stable isotopes, and total carbon. The average relative molar abundance of major cations and Si in ail stream waters follows the order Na^ (38%) > Ca^^ (25%) > Si (16%) > Mg^^ (15%) > K^ (5%). For major anions, the relative molar abundance is HCO3- (82%) > CI- (15%) > SO/- (3%) > P, Br, NO3- (all < 1%). Water near the head of all rivers has HCO3balanced by similar equivalents of Na^ Ca^^ and Mg^^ while higher salinity water in the downstream half of the rivers is dominated by Na and CI. Sources of dissolved ions include: (I) sea-derived airborne salts, with Na/CI and CI/Br ratios (freshwater) ranging from -39 to 445; (II) influx of saline groundwater contributing to CI/Br ratios similar to that of seawater and (III) rock-derived ions from weathering, contributing most of the observed HCO3-, Si and SO/" Ca^VSO/" ratios of > 1, as well as high and similar concentrations of both Cl- and SO/- indicate that dissolved SO/- is primarily derived from evaporate (gypsum and anhydrite) dissolution rather then sulphide oxidation. Large NO3/CI- ratios and increased concentrations of trace metals (i.e. Ba, Fe and Mn) for the rivers draining the northern flanks of the divide are due to the progressive input of either non-point or diffuse sources, such as licensed discharges of effluent from agriculture and light industry. All streams drain dry, tectonically stable and silicate-rich regions. Thus greater proportions of plagioclase (silicate) weathering to carbonate/evaporite weathering are expected. Average Na* values of < 1 prove that silicate weathering only plays a minor role in contributing cations to the river. By analogy with orogenic regions elsewhere in the world, the aim of this study is to exactly quantify the Sr^^ relative proportions of silicate vs. carbonate/evaporite weathering by identifying the sources of HCO3-, and SO/- under varying degrees of physical erosion and bedrock exposure, induced by sedimentologic and climatic regimes. Examination of relative dissolved species concentrations, determination of dominant mineral weathering reactions and mass balance calculations involving stable- (D^H, D^^O and D^^C) and radiogenic (®^Sr/®®Sr) isotope abundances of streams and bedrock will be used to determine the relative proportions of Ca^^ and Sr^^ from silicate and carbonate/evaporate weathering. Although geographically limited, the smallscale watersheds of the Victorian Alps (10's km^) have well defined hydrology and solute budgets and therefore present a key site in systematically examining the impact of meteorological, geological, and anthropogenic complexities on chemical weathering.

Keywords: Hydrogeology, chemical weathering, river chemistry

Email: Ben.Hagedorn@sci.monash.edu.au

2B

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

THE EFFECT OF GROUNDWATER INPUT ON STREAM SALINITY OF THE UPPER LODDON CATCHMENT, CENTRAL VICTORIA S.K. HAGERTY and J. A. Webb Department of Environmental Science, La Trobe University, Melbourne 3086, Australia

Surface water and groundwater in the Upper Loddon catchment, central Victoria, are used extensively for agriculture and domestic/urban supplies. However, beneficial use of water in the catchment and further downstream is threatened by salinisation, exemplified by the rising salinity levels in TuHaroop Reservoir. Protection and improvement of water quality and resources in the area requires knowledge of the processes affecting water and salt storage and movement, and a detailed study of the Tullaroop catchment was carried out for this purpose. The basement aquifer in the Tullaroop catchment consists of Ordovician bedrock; in the early Cenozoic this was incised by a palaeodrainage system that was then infilled by fining upwards sediments (sands/gravels to clays/silts), creating the deep leads. Covering the deep leads are several different basalt flows of the Pliocene/ Pleistocene Newer Volcanics; clay-rich soils separate some of the flows. The major aquifers in the area are the deep leads and basalts; the clayey palaeosurface between them acts as a leaky aquitard. Recharge both to the basalts and deep lead is thought to occur primarily through scoria cones that dot the landscape. Stream salinities are higher and more variable in creeks on the western side of the catchment. These streams reach a salinity "plateau" around 3000 [jS/cm during low flow periods in autumn, which may be due to seasonal groundwater input. Stable isotopes of O^® and H^ show significant groundwater inputs that are also correlated with areas of stream salinisation, predominantly in the west. Stable isotopes in Birch Creek, on the eastern side of the catchment, show a dominant rainfall signature. The difference in salt mobilization between the two streams is at least partly related to outcrop geology; in particular in the west there is a predominance of Ordovician basement outcrop, characterized by low-permeability clay soils that typically cause more saline recharge to the groundwater In addition, faults related to sudden changes in the thickness of the deep lead sediments may force deep lead groundwater to the surface in some parts of the catchment, providing a further input of salt to the streams.

Keywords: Hydrochemistry, Deep Leads, Murray Darling Basin, stable isotopes, groundwater - surface water interaction

Email: skhagerty@students.latrobe.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

DYKE CONTROLS ON GOLD MINERALIZATION: COHEN'S REEF, WALHALLA, SE AUSTRALIA M.HOUGH\ F. P. Bierlein^ and L. Ailleres^ ^ School of Geosciences, Monash University VIC 3800 2 Cente for Exploration Targeting, University of Western Australia WA 6009, Australia

Cohen's Reef is historically the most productive gold deposit in the Walhalla-Woods Point region of Eastern Victoria. Visible gold was mined from the laminated quartz reef, and to a lesser extent, the quartz-veined shear zones. The auriferous reef has a known strike length of 1.5 km and depth of over 1 km, and is spatially associated with the greater Woods Point Dyke Swarm, a 150-kilometre belt of N-NW trending dykes. Results from geochemical sample traverses proximal and distal to Cohen's Reef show that elevated gold values are associated with the sheared dyke margins. Is this simply due to the more competent nature of the dyke, and/or could it be due to its unique chemical composition? Almost 400 orogenic (metamorphic) gold deposits have been recorded within the Walhalla-Woods Point region. Of these, 35% are sediment-hosted, 6% are wholly dyke-hosted, 27% are sediment-hosted/dyke-associated and 26% are undefined. Although more gold deposits are not associated with dykes in the region, the amount of gold extracted from wholly sediment-hosted gold deposits is much less than that from dyke-hosted or dykeassociated deposits; eg. 552 kg Au (55.17 g/t) from Royal Standard Mine compared to 20643 kg Au (32.6 g/t) from the more productive Long Tunnel Mine (Cohen's Reef). The primary compositions found throughout the Woods Point Dyke Swarm, range from peridotite to granite, with gabbro the most common composition. Gold is most commonly associated with the more evolved diorite dykes. It has been established by previous workers that there is not a genetic link between the intrusion of the dykes (-376-378 Ma) and the hydrothermal activity linked with gold mineralisation (-372-374 Ma), although the relationship should be investigated as an exploration tool. The competent nature of the dyke bodies promotes brittle deformation, therefore forming pathways for the hydrothermal fluid. It is still to be established whether the dioritic composition of the dyke acts as a geochemical trigger, facilitating the precipitation of gold, or whether diorite dykes are simply more competent. The ability to visualise, in a 3D modelling framework, the extent of "Cohen's" dyke in association with Cohen's reef and gold grades, will enable a better understanding and predictive targeting of the mineralised system.

Keywords: Walhalla, Woods Point Dyke Swarm, gold mineralization, alteration, 3D modelling

Email: Megan.Hough@sci.monash.edu.au

2r

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

A FISHY PROBLEM: RELATIONSHIP ISSUES AMONG ARCHAIC FISH (OSTEICHTHYES: ACTINOPTERYGII) AND THE ROLE OF VICTORIAN RELICT TAXA IN RESOLVING THE CONFLICT M. P. INGLIS School of Geosciences, Monash University, Victoria 3800, Australia

Interrelationships of archaic basal actinopterygian fish are poorly known. Despite attempts to resolve the phylogenetics of this diverse group, limitations including incomplete and deformed specimens, poor preparation of fossils and alleged mistakes in the scientific literature have resulted in the problems seen today. It has been suggested that detailed descriptions of new specimens and revision of previously published taxa are needed before a serious attempt can be made to resolve the interrelationships of this group. The research summarised here demonstrates two examples of the former, with partial fish skulls from Dinosaur Cove being described for the first time. Dinosaur Cove in Victoria, southeast Australia, is an Early Cretaceous site, which was at that time located in southern polar latitudes. The unusual vertebrate assemblage includes relict taxa (including fish) that survived in possibly freezing, isolated conditions long after they went extinct elsewhere in the world. The Dinosaur Cove fish assemblage includes a distinct morphotype identified as cf. Holuridae. Another specimen resembles the subholostean Ptycholepis] this skull has been identified as cf. Ptycholepiformes. The fact that the specimens are incomplete and deformed precludes more accurate diagnoses. More complete and better-preserved specimens need to be found to test the validity of and refine the systematics of these archaic actinopterygian fish. It is hoped that these descriptions will provide valuable information of use in future studies of lower actinopterygians and their interrelationships.

Keywords: Osteichthyes, Actinopterygii, Palaeonisciformes, Holuridae, Ptycholepiformes, Early Cretaceous, Dinosaur Cove, Australia

Email: Matthew.lnglis@sci.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

ATOMIC FORCE MICROSCOPY STUDY OF FISSION TRACKS IN APATITE AND MUSCOVITE R KOHLMANN^ A. J. W. Gleadow\ B. P. Kohn^ and C. I. Pakes^ ^ School of Earth Sciences, University of Melbourne, Victoria 3010, Australia 2 Microanalytical Research Centre, School of Physics, University of Melbourne, Victoria 3010, Australia

Fission track analysis is unique in its ability to discern low temperature thermal histories of geological environments. Such thermal histories are fundamental to the understanding of a range of tectonic processes in the earth's crust, and their link to surface processes. In this radiometric dating method the decay is the spontaneous nuclear fission of ^^^U producing linear trails of radiation damage (ie fission tracks), from the passage of highly energetic fission fragment trajectories through the crystal lattice of the host mineral. Each fission event is accompanied by the release of about 210 MeV of energy, of which the majority (~170MeV) is the kinetic energy of the two fission fragments. These particles are propelled in opposite directions with energies ranging from 60 to 140 MeV The result of the energy deposited by a charged ionizing particle into a host mineral is a trail of damage within a narrow cylindrical region along the particle trajectory. This results in material in the damage zone becoming more chemically reactive than the surrounding undisturbed material, so that the trails can be enlarged by immersion in a chemical etchant and observed under an optical microscope. A properly etched fission track forms a nearly cylindrical hole pm in diameter and -16 |jm long in apatite [Ca5(P04)3(0H,F,CI), the mineral most routinely dated by this method]. The etch track geometry, which identifies the particle damage, can easily be measured using optical microscopy or scanning electron microscopy. With the development of near-field scanning probe techniques such as the Atomic Force Microscopy (AFM), it has become possible to image sample surfaces down to nanoscale. AFM observations of unetched tracks offer a powerful method for evaluating latent track parameters, thus providing fundamental information necessary to assess the changes undergone in a mineral due to the energy deposition associated with track formation. AFM images of muscovite surfaces irradiated by normally incident high energetic ions show crater-shaped bulges. The craters observed on muscovite have diameters between 16-28 nm. Several track openings have a pronounced raised rim that may represent the region of strained lattice around the track core. These new observations provide an improved understanding of fission track development. Future work will focus on obtaining further insights into the early track etching behaviour of muscovite and especially apatite. This will result in new, more precise determinations of the etching efficiency in apatites exhibiting a range of chemical composition.

Keywords: Atomic Force Microscopy, AFM, fission track, apatite, nanoscale, muscovite

Email: f.kohlmann@pgrad.unimelb.edu.au

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

BUTTERFLY NETS AND PITFALL TRAPS: NICHE BIASED PRESERVATION IN MIDDLE AND LATE TRIASSIC INSECT FAUNAS OF AUSTRALIA S. K. MARTIN School of Geosciences, Monash University, Victoria 3800, Australia

Historically, the Middle and Late Triassic insect faunas of Australia have been studied through four important localities. Middle Triassic assemblages occur in the Hawkesbury Sandstone (Anisian) and Ashfield Shale (Anisian-Ladinian) of the Sydney Basin, New South Wales; Late Triassic sites are known from the Mt. Crosby Formation (Carnian) and Blackstone Formation (late Carnian), Ipswich Basin, Queensland. These four localities are similar in that each pair of insect-bearing units are closely associated geographically and stratigraphically, and represent differing fresh water environments. Comparing previously described assemblages between the two Middle Triassic localities reveal very different insect faunas. The older Hawkesbury Sandstone is dominated by bugs (e.g. aphids, cicadas, planthoppers), with high numbers of grasshoppers and the extinct Titanoptera; the younger Ashfield Shale contains predominantly beetles, with numerous cockroaches and relatively fewer bugs. Interestingly, a similar pattern is discernible in the Late Triassic assemblages; the older Mt. Crosby Formation having a predominance of bugs, plus common grasshoppers and other groups, but only one cockroach species and no beetles, while the overlying Blackstone Formation has a very high diversity of beetles, common cockroaches and less dominant bugs and grasshoppers. Therefore, the Hawkesbury / Mt. Crosby localities seem to contain insects sampled from a forest canopy, as seen in the common vegetation-associated and moist woodland species - here termed the 'early association'. In contrast, the predominance of detritivorous and xylophagous (woodeating) ground-dwelling taxa at the Ashfield / Blackstone sites suggest a 'late association' of insects, sou reed from leaf-litter and undergrowth. Burial and post-burial taphonomic processes (transportation, diagenesis, etc.) appear not to have played a major role in shaping these two distinctive associations, as beetles and cockroaches are extremely sturdy and fossilise preferentially, if present. In addition, all four localities preserve insect wings of various sizes and levels of robustness. Instead, dissimilarity in the faunas may reflect pre-burial processes - the selection of insects representing not the whole fauna, but specific niches or microenvironments. Therefore, it is suggested that these associations show differences in the way specimens were trapped - the 'early association' preserving flying insects that fell into the water-body. 'Late association' insects were probably washed into the water-body, perhaps during heavy rainfall. This 'niche biasing' is one of many known factors affecting the fossilisation process, and understanding these taphonomic processes can help palaeontologists more accurately interpret the palaeoecology and palaeoenvironment of fossil assemblages.

Keywords: Triassic, insect, Australia, taphonomy, palaeoecology, palaeoenvironment

Email: Sarah.Martin@sci.monash.edu.au

3T

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

WATERBUGS (HEMIPTERA: HETEROPTERA) FROM THE LOWER CRETACEOUS KOONWARRA FOSSIL BED, GIPPSLAND BASIN, VICTORIA S. K. MARTIN School of Geosciences, Monash University, Victoria 3800, Australia

The systematics of the waterbug (Hemiptera: Heteroptera: Nepomorpha, Gerromorpha) fauna of the Lower Cretaceous Koonwarra Fossil Bed, of Gippsland, Victoria, was reviewed, and was found to include two species of semi-aquatic bugs (Gerromorpha) and one species of aquatic bug (Nepomorpha). Like other aquatic insect fossils known from Koonwarra, the bugs are preserved as nearly complete compressions in rock; however, in contrast to other aquatic groups, waterbugs are rare, with only six individuals known, drawn from a collection of over 400 specimens. All three species belong to families still living in Australia. Semi-aquatic bugs (Gerromorpha) are represented in the Koonwarra Fossil Bed by Duncanovelia extensa (Mesoveliidae, or 'water treaders') and one poorly preserved specimen attributed to the family Veliidae ('small water striders'). Aquatic bugs (Nepomorpha) are represented by three nymphs, which have been reassigned to the family Ochteridae (Velvety shore bugs'). All three taxa are predatory and semi-aquatic; ochterids and mesoveliids are predominantly marginal aquatic or littoral in habit, while veliids live on the water surface. Interestingly, all three specimens are relatively similar to the modern representatives of their respective families; e.g. Duncanovelia can easily be accommodated within an extant subfamily (Mesoveliinae), and closely resembles species within the extant genus Mesovelia. This suggests that by the Early Cretaceous the waterbug higher taxa (up to subfamily level) were already in existence and essentially modern, an idea supported by fossils from other waterbug-producing localities worldwide. Assemblages from other sites, such as the contemporaneous Santana Formation of Brazil, differ from Koonwarra in having waterbug faunas dominated by truly aquatic bugs, with few semi-aquatic taxa. In the Koonwarra assemblage, aquatic groups are entirely absent. Dominance of semi-aquatic taxa may reflect more on the nature of the Koonwarra water body, which has been reconstructed as a shallow and ephemeral lake, than the actual composition of the insect fauna of the time.

Keywords: Lower Cretaceous, Victoria, Koonwarra Fossil Bed, insects, Hemiptera, Heteroptera, palaeoenvironment

Email: Sarah.Martin@sci.monash.edu.au

32

— ^ ^ ^ ^ ^ ^ ^

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

BATHYMETRIC HIGHS AT SUBDUCTION ZONES W. G. MASON\ L.

M o r e s i ^

2

P. G. Betts^

^ School of Geosciences, Monash University, Melbourne 3168, Australia 2 School of Mathematical Sciences, Monash University, Melbourne 3168, Australia

Oceanic large igneous provinces (such as oceanic plateaus and ocean basin flood basalts), seamounts and seamount chains / ridges, remnant island arcs (formed on overriding oceanic plates at convergent margins) and ocean ridges (active or extinct) are all examples of bathymetric highs. It is inevitable that each of these highs will eventually interact with a subduction zone as the oceanic crust on which they formed converges with another tectonic plate. By comparing characteristics of bathymetric highs impinging upon convergent boundaries and their relative subduction zones, such as dimensions and relative buoyancy, we can gain a better understanding of the controls on how a bathymetric high may influence the morphology and geodynamics of a subduction system.

Keywords: large igneous province, oceanic plateau, seamount, subduction, morphology

Email: Wendy.Mason@sci.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

ALPINE MOSSBEDS: POPULAR MYTH OR UNPOPULAR REALITY? M. MCBAIN School of Geography and Environmental Science, Monash University, Victoria 3800, Australia

Studies of vegetation change and erosion threats in the Australian Alps overthe past 50 years have demonstrated that disturbance at the landscape-scale and point processes which concentrate at vulnerable points in the landscape can have long-term effects extending over centuries. Particularly in the catchments of hydroelectric schemes, the potential of cattle to exacerbate erosion was an early spur to scientific study of erosion potential. The role of mossbeds in retarding flow, from both flow rate and time-of-release aspects, has been repeatedly stressed in many studies. One of the key points made by opponents of alpine summer grazing was that the incursion of cattle into alpine mossbeds was an especially major trigger of destructive hydrological effects. However, there has been little of no evidence of quantitative measurement of the actual or likely magnitude of such effects in alpine catchments. This study examines one catchment in the Bogong High Plains of Victoria, which feeds directly into the head reservoir of the Kiewa Hydroelectric Scheme. Detailed distributed hydrological modelling for this small catchment, based on a photogrammetrically-derived high-resolution DEM shows that relative significance in terms of erosion potential can be assigned to the main study-area terrain components including vegetation types, soil depth and volume, mossbed depth and volume, catchment boundaries, flow accumulation points, flow direction and slope position.

Keywords: Catchment hydrology, landscape ecology, vegetation history, disturbance, grazing

Email: mjmcb1@student.monash.edu.au

W

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

GEOMETRY OF GEOLOGY AT BROKEN HILL, NSW, AUSTRALIA: TESTING PREVIOUS MODELS USING THREEDIMENSIONAL MODELS AND GEOPHYSICAL TECHNIQUES A. MCLELLAN, L. Ailleres and R. Weinberg Australian Crustal Research Centre, School of Geosciences, Monash University, Victoria 3800, Australia

The Broken Hill domain, NSW, Australia comprises a complex package of rocks known as the Willyama Supergroup. The area has undergone up to five deformation phases during the Olarian and Delamerian orogenies, which have caused significant deformation and metamorphism of the dominantly sedimentary rocks. The complex nature and structure of the rocks has given rise to several different hypotheses regarding the tectonic evolution and history of the Broken Hill domain and its 3D geometry. Two classically accepted geological models proposed for Broken Hill are compared to geophysical data, in the form of gravity and magnetic datasets. Comparison between the measured and the observed response is poor, particularly in northern Broken Hill, or the Sundown area. An intense low gravity anomaly does not fit the geology of the area at all, implying the proposed models are not an accurate depiction of rock geometry at depth. The occurrence of shallow lying intrusions at depth may be interfering with the measured gravity response; therefore dismissing the proposed models based on these results is unjust. In order to test this hypothesis, fieldwork was undertaken in the Sundown area to determine whether the existence of these intrusions is viable. 3D models were constructed using the intuitive geoscientific software package, 3D geomodeller. In-depth analysis of the Broken Hill Exploration Initiative petrophysical database is required to ascertain accurate rock properties to be assigned to different rock formations within each model. The close average density and magnetic susceptibility of typical metasedimentary rock packages in Broken Hill meant bi-modal and tri-modal distributions were determined to accurately represent the heterogeneous nature of the rocks. Initial results from inversion calculations suggest any tectonic model including these intrusions fit the geophysics over the area well.

Keywords: Broken Hill, geophysics, three-dimensional modelling, inversion, intrusion

Email: Andrew.McLellan@sci.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

AN ANALYSIS OF THE ANNULAR MODE INFLUENCE ON HYDROLOGICAL CYCLE VARIABILITY USING THE ^NUDGING' APPROACH B. MENEGHINI and I. Simmonds

SCHOOL OF EARTH SCIENCES, UNIVERSITY OF MELBOURNE, VICTORIA 3 0 1 0 , AUSTRALIA

The dominant patterns of atmospheric circulation variability in the Northern and Southern Hemisphere are known as the Northern Annular Mode (NAM) and the Southern Annular Mode (SAM), respectively. These modes exhibit two extreme phases, the positive phase and the negative phase. The positive (negative) phase may be characterised by higher (lower) pressures in the mid-latitudes and lower (higher) pressures In the high-latitudes. Variability in the annular modes leads to latitudinal shifts in the atmospheric jets, and mid- and high-latitude anomalies of opposite sign in a wide range of fields such as temperature, geopotential height and zonal wind. Annular mode variability over the last few decades has been dominated by strong positive trends (i.e. a tendency towards the positive phase). This has prompted a number of studies to be undertaken on the climate impacts of the annular modes. Studies on the association between the annular modes and precipitation have linked the SAM (NAM) to seasonal rainfall variability in parts of Australia, South Africa and South America (Europe and North America). These relationships are thought to be the result of the annular modes influencing the wind (and thus moisture transport) and synoptic activity (e.g. high and low pressure systems, cold fronts). There is however, a fairly incomplete picture of the hydrological cycle response to the annular modes because of relatively fewer studies on the association between the annular modes and evaporation, river runoff, soil moisture, atmospheric moisture content and depletion and restoration times. The aim of this study is to investigate the response of the hydrological cycle to annular mode variability, the mechanisms involved and the seasonality. Our approach will be to force the annular modes using a technique known as nudging, in the Melbourne University General Circulation Model, and the results of some nudging experiments will be presented.

Keywords: annular modes, atmospheric circulation, hydrological cycle, general circulation model

Email: b.meneghini@pgrad.unimelb.edu.au

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

VARIATION OF SYN-RIFT STRATIGRAPHY IN THE WOOLSTHORPE-COBDEN AREA, CENTRAL OTWAY BASIN, VICTORIA, AUSTRALIA - EVIDENCE FROM SEISMIC AND WELL DATA M. MiNARWAN, M. Hall and R. Cas School of Geosciences, Monash University, Clayton, Victoria 3800, Australia

Interpretation of seismic and well data of the Woolsthorpe-Cobden area, western Victoria, shows that the vertical stratigraphic succession of the syn-rift Crayfish Supersequence varies across different troughs. In the Warrong Trough the supersequence is up to 4 km thick and can be subdivided seismically into lower and upper packages, while in the Ballangeich and Garvoc Troughs it cannot be subdivided. The lower package in the Warrong Trough consists of two cycles of alternating, continuous, high amplitude and semi-continuous, low amplitudes reflections that overly a zone of low to moderate amplitude, semi-continuous reflections. Each cycle is interpreted as a sandstone unit that passes upwards into interbedded sandstone and shale. The upper package contains broad, semi-transparent to low amplitude, semi-continuous reflections as commonly exhibited by a thick, homogenous shale-dominated unit. A package of volcanic rocks, interpreted from the high amplitude, short to moderate length reflections, occurs at the bottom of the trough. Seismic reflection profiles of the Crayfish Supersequence in the Garvoc Trough show short to semicontinuous, low amplitude reflections interspersed with high amplitude, semi-continuous reflections. This package is up to 1.5 km thick and interpreted as sandstone-dominated with some interbedded sandstone and shale or coal in the upper portion. In the Ballangeich Trough seismic profiles show a package of low amplitude to semi-transparent, short reflections overlain by short, moderate to high amplitude reflections in the deepest part of the trough. This package is underlain by probable thin volcanic beds and is interpreted as sandstonedominated in the lower part, with minor interbedded shale and sandstone in the upper section. Wells indicate that sandstones dominate the early syn-rift sections in the area. This may be due to the low to moderate dips of the Tithonian-Barremian bounding faults, which means for a given extension the subsidence rate of the hanging-wall blocks was also low to moderate. The slowly subsiding troughs created less accommodation space than that of the high angle bounding faults and were more likely to contain dominantly coarse-grained sediments. The occurrence of interbedded shales and sandstones and shale-dominated sections in the upper Crayfish Supersequence of the Warrong Trough indicates underfilled accommodation space during the later stage of the rifting. The lack of thick, shale-dominated deposits in the Garvoc and Ballangeich Troughs is likely due to the limited accommodation space for sediment deposition at the time.

Keywords: Otway, Crayfish Supersequence, syn-rift. Lower Cretaceous, seismic stratigraphy, tectonostratigraphy

Email: mmin8@student.monash.edu

37

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

GEODYNAMICS OF THE GAWLER RANGE VOLCANICS, SOUTH AUSTRALIA: PHYSIOCHEMICAL AND TECTONIC CONSTRAINTS ON A FELSIC LARGE IGNEOUS PROVINCE M. PANKHURST School of Geosciences, Monash University, Victoria 3800, Australia

The Gawler Range Volcanics outcrop over 25,000 km^ of the central Gawler Craton and extend under neoproterozoic cover of the Stuart Shelf, South Australia. The Gawler Range Volcanics are the extrusive component of the Gawler Felsic Large Igneous Province. The dacite-rhyolite dominated Gawler Range Volcanics' preserved volume exceeds 40,000 km^, all of which was erupted at 1592±2 Ma, at the climax of the "Hiltaba Event", a regional thermal event that affected surrounding cratons such as the Curnamona Craton and Arunta and Mt. Isa inliers. The preserved upper Gawler Range Volcanics are voluminous peraluminous dacites and rhyolites that exhibit unusually high concentrations of halogens (fluorine and chlorine) and high eruptive temperatures (950-1100° C). Viscosity, total initial volume, tectonic, geophysical and geochemical investigations suggest that the upper Gawler Range Volcanics represent an extremely heavily eroded province with length scales and emplacement mechanisms similar to that of a shield volcano. Comparisons with other felsic large igneous provinces, re-evaluation of the geodynamic character of surrounding "intracratonic" and rift basins and other geodynamic considerations such as thermal bulging and magma sources reveal that the previously interpreted anorogenic setting of the Gawler Range Volcanics may be misleading, and that the Gawler felsic large igneous province could well have had a wider influence on the development of palaeoAustralia than is currently thought.

Keywords: Gawler Range Volcanics, Geodynamics, felsic large igneous province, viscosity, palaeo-Australia

Email: mjpani @student.monash.edu.au

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

GEOPHYSICAL MAPPING OF THE HUTCHISON GROUP BENEATH THE GAWLER RANGE VOLCANICS, GAWLER CRATON, AUSTRALIA N. J. PHILLIPS and P. G. Betts School of Geosciences, Monash University, Victoria 3800, Australia

The Palaeoproterozoic Hutchison group, located in the south eastern part of the Gawler Craton, forms a roughly north-south trending formation consisting of high-grade metamorphic clastic and chemical metasediments. The Hutchison group overlies Archaean basement (Sleaford Complex) and is intruded by Lincoln complex granitoids during the ca. 1740 - 1690 Ma Kimban orogeny. Aeromagnetics clearly show a north-south trending contrast between high and low magnetically susceptible units through Lincoln complex granitoids. This boundary forms the dextrally sheared ca. 1690 -1680 Ma Kalinjala fault which extends beneath the Gawler Range Volcanics province as a complex series of faults. The extrusion of the Mesoproterozoic Gawler Range Volcanics covered an extensive part of the Gawler Craton, including the Hutchinson Group with felsic lavas forcing regional geological interpretations to cease at the flow margins. Intense geophysical processing highlights the progression of the Hutchison group, Lincoln Complex and associated features such as faults and plutons beneath the Gawler Range Volcanics, as well as provided evidence of other geological features in the Gawler Range Volcanics and Stuart shelf provinces.

Keywords: aeromagnetic data, Gawler Range Volcanics, Hutchison Group, Gawler Craton, shear zone

Email: njphil @student.monash.edu.au

39

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

A MULTI-SCALE ISOTOPIC TRACER STUDY TO DELINEATE AQUIFER INTERACTIONS AND THEIR IMPACT ON GROUNDWATER SALINISATION IN THE EASTERN HOPKINS CATCHMENT, VICTORIA, AUSTRALIA M. RAIBER and J. A. Webb Department of Environmental Geosciences, La Trobe University, Bundoora 3083, Victoria, Australia

A regional scale sub-basaltic palaeodrainage system covering an area of more than 2000km2 lies beneath the gently undulating landscape of the eastern Hopkins catchment in Victoria, Australia. This palaeodrainage system contains several sequences of fluvial sediments consisting of gravel, sand, ligneous clays and coal assigned to the early Cenozoic Eastem View Formation. These sediments were sealed in place by the basalts of the Newer Volcanics, erupted during three phases (distinguishable on radiometric images), ranging from about 6 Ma to a few thousand years ago. Groundwater quality within the Eastern View Formation and the basalt aquifer is highly variable, ranging from drinking water quality in the vicinity of eruption points to highly saline groundwater down-flow of the eruption points. In order to understand what causes these differences and to get an understanding of the recharge and flow mechanisms, we have applied several natural chemical and isotopic tracers (®^Sr/®®Sr, D^^O, D^H, D^^C, tritium and radiocarbon). The isotope data show that groundwater in close proximity to eruption points are comparatively young, both in the basalt aquifer and the underlying Eastern View Formation, while they become progressively older with increasing distance down flow from the eruption points. A hydraulic head difference map constructed for the Eastern View Formation and the basalt aquifer demonstrates that there are strong downwards hydraulic trends from the basalt aquifer into the Eastern View Formation in the vicinity of eruption points, while there is zero head difference in most other areas. We therefore conclude that the Eastern View Formation and the basalt aquifer are hydraulically separated by an aquitard, except where eruption points penetrate this aquitard, and that the Eastern View Formation is predominantly recharged through the eruption points and the youngest basalt phase (associated with rocky outcrops and thin soil covers), while there is no or only limited interaquifer leakage in most areas.

Keywords: palaeodrainage system, groundwater salinity, isotopic tracer

Email: mraiber@students.latrobe.edu.au

40

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

THE ROLE OF MAGMATIC AND EXHALATIVE ROCKS IN THE BROKEN HILL SYSTEMS: GEOCHEMICAL AND ISOTOPIC EVIDENCE M. RAVEGGP, D. Giles', J. Foden', M. Raetz' and I. Nicholls' ^ Australian Crystal Research Centre, School of Geosciences, Monash University, Victoria 3800, Australia 2 School of Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia

We present geochemical (major, traces and REE) and isotopic (Sm-Nd and U-Pb) data from ca 1685 Ma high Fe-Ti mafic rocks (amphibolites), the Alma, Rasp Ridge and Hores-Potosi Gneisses, metasediments and "exhalites" from the Broken Hill Inlier in western New South Wales. Our data confirms the ensialic rifting event in the Curnamona Province between ca 1710-1685 Million years, adding that rifting had reached thin lithosphere conditions by ca 1685 Ma and placing the Broken Hill Inlier in a central position of the developing basin. We infer a depleted mantle source (asthenosphere) for the mafic rocks and that Fe-Ti enrichment present in these lithologies is a result of fractional crystallisation or by AFC with small rates of assimilation to fractionation (r = 0.05-0.2) leading to melts with up to fep^^^^^^ - 2 5 wt % and 1102-4.2 wt %. The Alma and Rasp Ridge felsic melts were generated by anatexis of crustal material from the Willyama Supergroup sedimentary pile. The geochemistry of the Hores-Potosi Gneiss is best explained by mixing between these crust-derived melts and a juvenile mantle derived component, represented by the coeval mafic lithologies. The data on the exhalites is consistent with an origin via hydrothermal activity, with the fluids responsible for their deposition in equilibrium with the Willyama supracrustal sequence. We infer a crustal dominated source for the Pb of the Broken Hill orebody, with its metals provided by the Willyama Supergroup supracrustal pile. Exhalite deposition and Broken Hill orebody formation were coeval with the ca 1685 Ma magmatic activity.

Keywords: high Fe-Ti mafic rocks, Alma, Rasp Ridge and Hores-Potosi Gneisses, exhalites, Willyama Supergroup, Broken Hill

Email: Massimo.Raveggi@sci.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

RECENT ENVIRONMENTAL CHANGES AND HUMAN IMPACT ON THE GIPPSLAND LAKES, VICTORIA K. SAUNDERS and A. McMinn Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Hobart, Australia

The Gippsland Lakes form the largest estuarine system in Australia. They are recognised as wetlands of international importance and are listed under the Ramsar convention. However, there are many environmental and ecological concerns facing the Gippsland Lakes, which have arisen as a result of the management and use of the lakes and surrounding catchment since the arrival of Europeans in the 1840s. Extensive areas of the catchment have been cleared for agriculture, industry, forestry and urban development. Nutrient and sediment inputs have increased dramatically and extensive algal blooms commonly occur. An artificial opening was constructed in 1889 resulting in a more marine environment. Improving the water quality of the Gippsland Lakes has become an important issue. However in order to do this successfully, background information is required. While there has been monitoring undertaken since 1986, little historical information is available to allow an assessment of the extent of changes since European settlement. Using a palaeoecological approach, this project aimed to reconstruct changes occurring in the last 200 years. Firstly, a diatom-nutrient transfer function based on 57 sampling sites from Victorian coastal lagoons and shallow bays was developed using weighted averaging partial least squares, two components (r^ = 0.84, r^g^^ = 0.65, RMSEp = 0.52). This was applied to a 175-year sediment core from Lake King, Gippsland Lakes. Results indicate that there have been substantial environmental changes and human impacts during the last 175 years and Lake King has changed from a fresh-brackish lake, dominated by planktonic diatoms to a more brackish-marine system dominated by a combination of benthic and planktonic diatoms. Results suggest that stratification and algal blooms occurred prior to and during the early settlement period. This is part of a larger study currently undenA^ay that includes Tasmania. Our preliminary data show that a palaeoecological approach may be used to reconstruct changes in nutrient status and human impact over time. It also has potential future management applications in southeast Australia, both in helping to restore heavily impacted sites and in ensuring the effective conservation of the region's remaining virtually pristine coastal habitats.

Keywords: Palaeoecology, diatoms, nutrients, southeast Australia, human impacts, estuaries

Email: saunderk@utas.edu.au

4T

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

EVIDENCE OF MULTI-SOURCE PROVENANCE FOR EARLY CRETACEOUS SEDIMENTS IN THE GIPPSLAND BASIN D.E. SEEGETS-VILLIERS School of Geosciences, Monash University, Victoria 3800, Australia

A multiple source of origin has been established for Early Cretaceous fluvial sediments from the coastal area of Inverloch, Gippsland Basin, Victoria. Thin section analysis revealed a metamorphic and reworked component in addition to the previously postulated volcanic sediment source. A contemporaneous volcanic province situated towards the east of the Gippsland Basin is favoured as a source for these sediments by some workers. Palaeocurrent data however indicate a provenance deriving from a southwesterly direction supporting a contemporaneous rift based volcanic source proposed by others. Palynological analysis has furthermore identified a small but consistent and well preserved pre-Cretaceous element, most likely of Late Triassic age. Identifying the source of these palynomorphs is difficult as Late Triassic surface or subsurface rocks in close vicinity to the site are not known. Transport from greater distance is difficult to envisage due to the very good preservation of reworked material. A widespread Triassic sediment cover very likely existed in most areas of the Gippsland Basin but can only be established after more detailed work.

Keywords: Early Cretaceous, Gippsland Basin, palynology, sedimentology

Email: doris.seegets-villiers@sci.monash.edu.au

43

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

PALAEOECOLOGICAL SIGNIFICANCE OF THE PLEISTOCENE FOSSIL DEPOSITS OF THE BUCHAN CAVES, SOUTHEAST AUSTRALIA D. A. SHEAN School of Geosciences, Monash University, Victoria 3800, Australia

The Buchan Caves, located in eastern Victoria, southeast Australia, contain a diverse Pleistocene-aged fossil fauna. These deposits are of significance in palaeoecological correlations and reconstruction of Pleistocene environments within Australia. Prominent within the assemblage is the middle-late Pleistocene marsupial megafauna, including Protemnodon anak, Protemnodon sp., Simosthenurus occidentalism Sthenurus sp., Vrocoptodon' gilli, Thylacoleo carnifex, Zygomaturus trilobus, Palorchestes azael and P parvus. In addition there is a diverse selection of regionally extant fauna, including species of dasyurid, bandicoot, possums, kangaroo and rat kangaroo, wombat, bat, reptile and bird. Regionally extinct species that still occur elsewhere are also preserved (e.g. bandicoots, mountain pygmy possum, swamp and rock wallabies, koala, water rat). This assemblage may reflect a range of environmental conditions from the late Pleistocene through Recent. Various seeds and pollen, useful for environmental interpretation are observed within the deposits. Using a combination of pollen/seed analysis, taxonomy and dating techniques, palaeoecology, palaeoenvironment and age of the fauna can be determined. The diversity of fossil material coupled with palynology implies changes in environmental conditions through the Pleistocene from dry open sclerophyll forests, to wetter closed forests, and finally to dry open grassland.

Keywords: Pleistocene, Australia, Buchan Caves, palaeoecology, megafauna, palynology, environment

Email: dino_girl28@hotmail.com

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

A CASE OF MISTAKEN IDENTITY: CHANGES IN THE ARTISTIC RESTORATIONS OF THE PLEISTOCENE MARSUPIAL PALORCHETES AZAEL D. A. SHEAN School of Geosciences, Monash University, Victoria 3800, Australia

Scientific and artistic restorations have a great influence on the prevailing views regarding animal form and function expressed to the wider scientific and public communities. In some instances, the illustrative bias can influence and compound erroneous scientific conclusions. Sir Richard Owen described the Australian Pleistocene marsupial Palorchestes azael in 1873 as a "3m tall kangaroo", a concept eagerly embraced by museums and artists alike. In his 1873 paper, Owen had illustrated the maxillary component he had described and superimposed this fragment upon a schematic reconstruction of what the skull of this animal would have looked like. In 1946 J.T Woods determined that Palorchestes azael was in fact not a kangaroo at all, rather it was a large quadruped much like Diprotodon optatum. In silent embarrassment, many of the previous reconstructions were then destroyed. During the period 1980 through 2000 a favoured depiction of Palorchestes was as a trunked marsupial ripping at bark, perhaps for consumption. This was largely due to the discovery of the skull of a geologically earlier species, the late Miocene Palorchestes painei, and an associated skeleton (including limb bones) of Palorchestes azael. Recent research into the cranial morphology of Palorchestes azael casts doubt on the substance behind earlier artists' life restorations of this species. Generation of new scientific information, including rostral and cranial morphology, have ramifications for both previous environmental and dietary preferences attributed to this animal and the science behind illustrative reconstructions. Analysis of the skull morphology of P azael, and comparison with extant mammals, suggest that there is no unambiguous evidence in support of the notion that Palorchestes azael possessed a tapir-like prehensile proboscis, instead it may have borne a broad rhinarium or arched nasal structure.

Keywords: Palorchestes azael, trunk, nasal, diet, illustration, reconstruction

Email: dino__girl28@hotmail.com

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

USE OF GEOPHYSICAL METHODS TO IDENTIFY SEEPAGE FLOW FROM A MINE TAILINGS DAM, ZINIFEX, WESTERN TASMANIA V. R. TAMMIREDDY and J. E. Reid Private Bag-79, School of Earth Sciences & C.O.D.E.S, University of Tasmania, Hobart, Tasmania 7001, Australia

Geophysical methods, including self-potential, mise-a-la-masse, resistivity/induced polarisation, and frequency and time-domain electromagnetic have been implemented in trials to detect and monitor seepage from a disused mine tailings dam in western Tasmania. Repeat surveys have been conducted at intervals of a few months over a two year period. Resistivity/Induced polarisation imaging was conducted in order to distinguish between high water and clay content within the dam wall. Strong self-potential anomalies were observed to be associated with the major seepage zones from the dam and self-potential and mise-a-la-masse data have been used to identify likely seepage pathways through the dam wall.

Keywords: Seepage, self-potential, mise-a-la-masse, resistivity, induced polarisation, electro-magnetic, tailings dam, seepage pathways

Email: tammireddy495@yahoo.com

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

3D GEOTHERMAL MODELLING - HOW DOES HEAT TRANSFER THROUGH STRATIGRAPHY AND DISCONTINUITIES IN A SEDIMENTARY BASIN? T. P. TRIANTAFILLOU, G. R. Beardsmore and L. Ailleres

School of Geosciences, Monash University, Victoria 3800, Australia

Geothermal energy emanates from the Earth's interior. At the crystal scale, understanding how heat distributes itself provides predictive capabilities in resource exploration. 3D heat distributions have implications for organic matter maturation models (oil and gas exploration) and can be direct targets for geothermal energy explorers. In one dimension, heat distribution is straightforward to model; in that lateral conditions are not considered and the underlying mathematics are simple to compute, but this methodology does not accurately reproduce any horizontal gradient that may be present in a 3D space. However, modelling this distribution in 2 or 3D poses its own problems in defining the heat flow acting in a system. Setting constraints when measurements are scarce increases the importance of suitable boundary conditions that do not adversely inhibit the model's accuracy or neglect to respect physical laws. We present a method that numerically models temperature distribution in 3D. Initially surface temperature is zero unless there is a known data point and surface heat flow is defined from field measurements. The first step consists of a vertical propagation of both the temperature field and heat flow and reconciliation with boundary condition at the surface (observed surface values). The second step propagates this initial distribution horizontally. It is assumed that the model box has no lateral heat flow. Preliminary results show that: (1) it is difficult to define a suitable algorithm that represents the distribution of heat without over-influencing the system; (2) assumptions can result in thermal anomalies being over- or underestimated; (3) sedimentary units, with their comparatively lower thermal conductivity, act as a thermal blanket covering heat generating granites; and (4) these granites transfer heat to surrounding units by conduction in a distribution representative of the originating unit's geometry.

Keywords: Geothermal, numerical modelling, thermal conductivity

Email: tptril @student.monash.edu.au

T7

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

BIOREMEDIATION OF AN ACIDIC MINE LAKE AT WENSLEYDALE, VICTORIA T. T U i r , J. Sherwood^ and B. Knight ^ School of Life and Environmental Sciences, Deakin University, Victoria, Australia 2 Alcoa Anglesea, Victoria, Australia

Alcoa operate an open cut brown coal mine near Anglesea, southwest of Melbourne in central coastal Victoria. Closure and rehabilitation is likely in approximately 15 years, with the preferred end use being a useable pit lake. The void's geological and morphological characteristics combined with regional acid drainage are likely to retard development of a 'healthy' lake. A nearby 40-year-old coal mine lake (Wensleydale) has been the site of 12 month field bioremediation experiments to further understanding of acid lake remediation. Wensleydale (^3000 ML) lake is still mildly acidic pH -5.0 and in general has very low productivity and biodiversity. The primary inhibitors of natural restoration were identified as ongoing acid inputs (adjacent springs pH 3.0), limited allochthonous inputs of carbon and nutrients, the great relative depth of the lake (mean depth 20.5 m) and limited area of littoral zone (-20% of aerial extent is < 5m depth). The size of Anglesea mine lake is likely to be in the order of 50,000 ML, and the same inhibitors as at Wensleydale will affect restoration. Passive bioremediation treatment, using sulphate-reducing bacteria (SRB), is the preferred technique based on environmental and economic criteria, but is still at the research and development stage internationally. To test the potential of passive bioremediation, 6 mesocosms (limnocorrals) 1.2 m diameter and 16 m long were installed in-situ at Wensleydale. Applications of a sediment substrate (a combination of biosolids from wastewater treatment and chipped green waste) were added to stimulate SRB activity in 4 of the mesocosms with the remaining 2 to act as controls. The experiment was run over 12 months and monitoring of a range of parameters was undertaken monthly. It was found that a dose of 2 g/L biosolids and green waste could induce anoxic/anaerobic conditions in the deep hypolimnion and promote SRB activity. An increase in pH of ~ 1.5 units was measured and alkalinity increased from 0 to 60 mg/L (CaCOg equivalents). Total phosphorus increased in concentration by almost an order of magnitude (from 0.015 mg/l to 0.14 mg/L). The study has shown that bioremediation of water quality can be achieved in a lake environment at viable application rates. To give some perspective on this, the process could use 10 years of the region's biosolids and green waste production.

Keywords: acid, mine, lakes, bioremediation

Email: ttut@deakin.edu.au

4H"

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

LASER ABLATION ICP-MS OF MELT INCLUSIONS IN THE NORTHPARKES PORPHYRY COPPER DEPOSIT M. VAN DONGEN, R. F. Weinberg and A. G. Tomkins School of Geosciences, Monash University, Victoria 3800, Australia

Porphyry copper deposits are low grade, large tonnage deposits, which form in response to fluid exsolution from a crystallizing, decompressed felsic magma In the upper crust. They occur in arc settings and are commonly associated with oxidised magmas. Mass balance calculations suggest that the amount of sulfur present in these deposits is greater than can dissolve in the felsic magmas. We are investigating the additional source of sulfur that is required, and hypothesise that mafic magma input into felsic magma chambers may provide the excess sulfur. We have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyse selected major and trace element contents of heterogeneous melt inclusions from the Northparkes porphyry copper-gold deposit in New South Wales. Trace elements are sensitive indicators of magmatic processes. Melt inclusions represent tiny pockets of melt that were trapped in phenocrysts during growth, and thus may reflect the melt composition at that time. Therefore, this is a suitable technique to investigate the hypothesis. In addition, we have analysed the platinum group element (PGE) geochemistry of sulfides using LA-ICP-MS. PGE ratios may show involvement of immiscible sulfide phases during magmatic evolution. Results show that laser ablation analysis of heterogeneous melt inclusions can provide a qualitative understanding of the inclusion geochemistry, but is generally poor in resolving quantitative issues, due to a number of uncertainties inherent to this type of approach. More work is needed to interpret the PGE signatures of ablated sulfides.

Keywords: sulfides, trace elements, ore genesis

Email: michiel.vandongen@sci.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

IMPACTS OF FOREST AGE ON WATER USE IN MOUNTAIN ASH FORESTS S.A. WOOD and J. BERINGER School of Geography and Environmental Science, Monash University, Victoria 3800, Australia

The water for the city of Melbourne, Australia, is obtained from 1570 km^ (157,000 hectares) of forested catchments located in the Victorian Central highlands. Mountain Ash {Eucalyptus regnans) forests cover half of the catchment areas yet this area yields approximately 80% of the stream flow that makes up Melbourne's water supply. Historical fires have resulted in the destruction and subsequent regeneration of these forests and have altered the patterns of runoff into catchments. In addition, climate change will influence the evaporation and transpiration (e.g. water use efficiency) from the catchment. Such alterations could have important feedbacks to the catchments and Melbourne's available drinking water. This study aims to understand and quantify the water use of Mountain Ash trees and how this water use changes with stand age, through a comparison between three different aged stands via sap flux measurements. The data will be used in conjunction with eddy covariance observations to determine the amount of water used by undergrowth and overstorey trees in an old-growth stand. The results show that water use between the different age Mountain Ash forests decreases substantially, but the water use of the different aged stands as a whole (overstorey plus understorey) shows no real change in water use with forest age. These results are further supported by the eddy covariance results.

Keywords: Eucalyptus regnans, runoff, water use, sapwood, sapflow, heat pulse method, transpiration

Email: sawoo4@student.monash.edu.au

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Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

NEW EVIDENCE FOR THE POSSIBLE EXTENSION OF NORTHWESTERN TASMANIA INTO SOUTHERN VICTORIA C. H. WOOF School of Geosciences, Monash University, Victoria 3800, Australia

The possible extension of Neoproterozoic-Cambrian mafic and ultramafic lithosphere of north-western Tasmanian beneath central Victoria (the Selwyn Block concept), has long been documented. Traditionally, evidence in support of the Selwyn Block concept includes the geochemical similarities of the Victorian Mt Stavely and Heathcote greenstone belts to the Tasmanian Mount Read Volcanics, the continuity of three magnetic anomalies between north-western Tasmania and southern Victoria, and the presence of Cambrian ultramafic rocks in Bass 2 drill core, which indicates the extension of the crust to at least half way between Tasmania and Victoria. Recent petrographic analysis of the tholeiitic Maitland Beach Volcanics from the Waratah Bay coastline of southern Victoria revealed recrystallisation of augite phenocrysts within these pillow basalts to an unusual granoblastic texture. Electron microprobe analysis of the Ca content of the clinopyroxene grains from either end of the Maitland Beach outcrop confirmed initial expectations that exposures at Bear Gully underwent more extensive recrystallisation than outcrop near Walkerville South. Additionally, significant variations in Al, Ti, V, Cr, Mg and Fe content between the augite phenocrysts present at these two locations was noted. Petrographic analysis of Neoproterozoic-Cambrian mafic rocks from the Penguin shoreline in northwestern Tasmania suggests similarly recrystallised clinopyroxene. Should electron microprobe data indicate a similar chemical composition of the clinopyroxene grains to those of Maitland Beach, and should the bulk rock major and trace element geochemistry also support correlation of Penguin with Maitland Beach then this would constitute new evidence in support of the Selwyn Block concept.

Keywords: Selwyn Block, Penguin, Maitland Beach Volcanics Email: chwoo3@student.monash.edu.au

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Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

A FRAMEWORK FOR MODELLING LANDSCAPE DYNAMICS AND THEIR IMPACT ON COOL TEMPERATE RAINFOREST IN THE STRZELECKI RANGES, VICTORIA Z. ZHANG Centre for GIS, School of Geography and Environmental Science, Monash University, Victoria 3800, Australia

Land use/land cover change is increasingly recognized as an important driver of environmental change on all spatial and temporal scales. Land use/land cover change contributes significantly to earth atmosphere interactions, forest fragmentation, and biodiversity loss. It has become one of the major issues for environmental change monitoring and natural resource management. Substantial change of Australia's land cover has occurred since European settlement, mainly as a result of agricultural development. Land with forests and other native vegetation was cleared for farming. Land clearing has a significant long-term impact on natural environment at national, state and regional scales. Land use and land cover changes affect a range of landscape functions, resulting in the loss of biodiversity, soil salinity, and land degradation. Nowadays, there is a growing awareness of the importance of the better understanding of land use and land cover changes for efficient environmental management and sustainable development. Like other areas in Australia, landscapes in the Strzelecki Ranges of SE Victoria (Australia) have undergone significant change due to land clearing and natural disturbances such as bush fire and weed invasion. One of the direct results of this change was a significant reduction in the total extent and quality of native vegetation across the Strzelecki Ranges. However, details of land cover changes and their influence on the environment, especially on the distribution of cool temperate rainforest in this area is unknown. The different land use patterns have different influences on imbedded remnant patches of cool temperate rainforest mainly through edge effects. When the surrounding landscape patterns change, the environmental conditions (e.g., microclimate) produced along these edges (the boundaries between surrounding forests and the cool temperate forest) are modified and influence the interior cool temperate forest. Edge effects are the result of the interaction between two adjacent ecosystems when the two are separated by abrupt transition (edge). The extent and magnitude of edge effects is affected by landscape structure such as patch size, patch shape and orientation. A framework is proposed as the first step to model the long term landscape dynamics (starting from the 1930s) in the Strzelecki Ranges by integrating remote sensing, geographical information system (GIS), and landscape metrics, and to assess the impacts of different land use patterns on cool temperate rainforest in the Ranges.

Keywords: Landscape dynamics, landscape metrics, land cover change, remote sensing, GIS, rainforest

Email: Zhenyu.Zhang@arts.monash.edu.au

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Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

MINING AND RESERVOIR TRIGGERED EARTHQUAKES, AND ANTICIPATION OF FUTURE EVENTS

G.GIBSON Earthquakes in stable continental regions are often directly or indirectly associated with mining. The most active area in Victoria over the past 50 years has been south and north of the coalfields of the Latrobe Valley. The most damaging Australian earthquake was under the Newcastle coalfields during 1989, and during 1994 another shallow event of similar magnitude was under the Cessnock coalfields near Ellalong. The majority of the other recent New South Wales moderate magnitude earthquakes have been under or near to the coalfields south and west of Sydney. There have been many mining triggered and induced earthquakes in Australia, especially in Western Australia. The vast majority of South African earthquake activity is in the underground mining area.

By world standards the upper crust in Australia experiences very high horizontal compressive stress, and the majority of earthquakes occur on reverse faults. There is a considerable reserve of strain energy built up within rocks at shallow depths. This results in Australian earthquakes being at depths shallower than is usual, and probably contributes to the high proportion of reservoir and mining triggered earthquakes.

There are similarities and differences between triggered earthquakes and normal tectonic earthquakes, and it is possible to learn from the characteristics of each. A more complex model of earthquake clustering than was used in the past is now offering the possibility that some earthquakes may be forecast (with probability), although earthquake prediction (with certainty) seems impossible. Study of the highly clustered character of triggered earthquakes, and the relationship between the trigger mechanism, the stress field, and the resulting triggered events should lead to some improvements in anticipation of future events.

RESEARCH INTO SEISMIC ACTIVITY IN THE DEEPER LEVELS OF THE PASMINCO BROKEN HILL MINE W. PECK There is a history of microseismic activity in the deeper levels of the Broken Hill mines, with the larger events being strongly felt by the miners underground and occasionally being also felt by residents in their homes. An average of 10 events occurred on those days when no major openings (stopes) were being created, rising to about 30 events per day during periods of stope creation. The footwall (eastern side) of the orebody, is noticeably more seismically active than the hanging wall. Many of the events appear to be the result of crushing and shearing of highly stressed rock in the walls and backs of mine development openings. A new set of joints (that were not present a few days earlier) was generated at the focus of one event.

A case study will be presented of a cluster of 16 microseismic events that occurred over a half-hour period at a relatively quiet period in the mine, with no blasts in the vicinity on that day and no stope creation activities having occurred for several weeks. Three of the events were "felt in town" and many were located in the walls and backs of mine openings frequently traversed by miners. It was simply a matter of good luck that no one was in the vicinity at the time.

Computer analyses show there is an excellent correlation between microseismicity and the increase in shear stress along joints. However, no basis was found at Broken Hill that would permit forecasting of the time and location of future seismic events.

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

THERMAL HISTORY RECONSTRUCTION FOR EXPLORATION OF HYDROCARBON USING APATITE THERMOCHRONOLOGY: AN EXAMPLE FROM KRISHNAGODAVARI BASIN, EAST COAST OF INDIA H. S. SAHU, M. J. Raab, A. Gleadow and B. Kohn School of Earth Sciences, University of Melbourne, Victoria 3010, Australia

Thermal history analysis is crucial for the hydrocarbon prospect assessment of sedimentary basins. It estimates the temperature history of sedimentary layers in a subsiding basin with respect to time, which helps make predictions of the amount of hydrocarbon generated. Integrated analysis and modelling of apatite fission track and vitrinite reflectance data is a powerful technique to constrain precise thermal histories. In the present study we aim to obtain a comprehensive picture of the hydrocarbon habitat of the Krishna-Godavari Basin using this method. The Krishna-Godavari Basin, a pericratonic basin, is located along the east coast of the Indian peninsula. This petroliferous basin, fed by Krishna and Godavari rivers, contains thick sequences of sediments with several cycles of deposition ranging in age from Late Carboniferous to Holocene. The basin's high geothermal gradient coupled with the thick, Tertiary sedimentary package km) creates a favourable environment for source rock maturation. 153 samples (both cores and cuttings) from 10 deep drilled boreholes including 2 offshore wells and 50 hinterland surface samples have been collected and processed for apatite fission track analysis. Analysis and modelling of these samples will allow the identification of significant heating episodes in the past, in which rocks reached palaeotemperatures that might have been higher than their present temperatures in the basin. It will quantify the effects of these palaeothermal episodes and the timing of cooling from maximum palaeotemperatures. Thus a thorough understanding of the thermal history of the basin will be possible. Combination of organic maturity data (vitrinite reflectance) with fission track will provide tighter constraints on the palaeogeothermal gradient and eventually the burial and thermal history of the basin. Low temperature thermochronology on hinterland rock types will provide information on the amount of denudation through geologic time brackets as well as the sediment types being discharged into the basin. It might also offer useful information on the longstanding controversy of the origin of Rajahmundry basalt flow near the basin and can be correlated with the formation of Deccan Traps. Mass balance models will be created incorporating the removal of crustal material from the continent and its redistribution onto the continental shelf, taking the volume of sediment deposited offshore into account.

Keywords: Krishna-Godavari basin, apatite fission track analysis, thermal history, denudation Email: h.sahu@pgrad.unimelb.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

POST BREAK UP TECTONIC REACTIVATION AND DENUDATIONAL EVOLUTION IN THE KAOKO BELT, NAMIBIA: A THERMOCHRONOLOGICAL STUDY F. F. LUFT, M. J. Raab, B. Kohn and A. Gleadow School of Earth Sciences, University of Melbourne, Victoria 3010, Australia

Post Gondwana break-up tectonic reactivation has been recorded in the Kaoko Belt, NW Namibia, 60 Ma and possibly 75 Ma after the commencement of South Atlantic spreading. Evidence for these reactivations comes from the preservation or absence of Etendeka Province volcanism (ca. 130 Ma) and unconformities in the adjacent offshore Walvis Basin stratigraphy. This study aims to investigate the low temperature evolution for. the Kaokoveld in order to establish a temporal and spatial link between tectonic reactivation and denudation history for this part of the Namibian continental margin. In order to establish these links, we applied apatite fission track thermochronology (AFTT) and apatite (U-Th)/He dating for a set of samples collected orthogonal to the main NNW structures of this belt (Sesfontein Thrust, Purros and Three Palms Shear Zones). The Purros Shear Zone (PSZ) is an important crustal scale structure that sub-divides the Kaoko Belt into different tectono-stratigraphic and metamorphic zones. In addition, based on geological evidence between the Proterozoic basement and Early Cretaceous Etendeka basalts, the PSZ is interpreted as a post Early Cretaceous reactivated shear zone. Our preliminary apatite fission track and (U-Th)/He data sets present ages varying from 49±4 Ma to 297±26 Ma, indicating distinct cooling events in the Early and Late Cretaceous and another possible event in the Early Eocene. The Early Cretaceous (130 Ma) event is related to Gondwana break-up and consequent generation of the South Atlantic Ocean. The subsequent Late Cretaceous event (-70 Ma) is in accordance with previous work for central Namibia and is related to the change in spreading direction in the southern Atlantic Ocean. Finally, the Early Eocene event (-55 Ma) corresponds to a major unconformity in the Walvis Basin and may be interpreted as the result of base level adjustments possibly related to the tectonic reactivation of the adjacent basement structures. This project will thus not only determine the landscape evolution of the Kaokaveld since the Great Escarpment generation in the Early Cretaceous, but also quantify the tectonic reactivation and subsequent denudation for Northern Namibia, determining possible vertical displacements between crustal blocks and consequent correlation with the stratigraphic record in the adjacent offshore basins.

Keywords: Tectonic reactivation, denudation, apatite fission track thermochronology, apatite (U-Th)/He dating, Purros Shear Zone, Kaoko Belt, Namibia Email: ffernandesluft@pgrad.unimelb.edu.au

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

Geological Society of Australia Abstracts 83

FEATURE EXTRACTION AND VISUALIZATION WITH LIDAR DATA IN RURAL AREAS X, LIU Centre for GIS, School of Geography and Environmental Science, Monash University, Victoria 3800, Australia

Features such as road networks, trees, wetlands, and water sources are very important information for environmental management in the rural area. The extraction of features from high resolution remote sensing imagery offers a main source of data for environmental applications. Some texture analysis techniques have been developed by using different criteria for feature extraction, including statistical methods, filter techniques, and the most recent techniques based on wavelet decomposition. These methods are working well for extracting features from different resolution aerial photography or satellite imagery, but not sufficient for the new dataset such as Light Detection and Ranging (LiDAR) data. Traditionally, features extracted from imagery only show the horizontal positions because the imagery does not have height information. 3D feature extraction has been achieved by using stereophotogrammetric tools, needing a significant amount of manual labour. LiDAR, an emerging technology, offers capability of capturing high density three dimensional points. LiDAR system records multiple-return data if the laser beam hits on the vegetation and buildings. This multi-return data can be used to generate high accuracy and high resolution Digital Elevation Model (DEM) and Digital Surface Model (DSM) in a fast and cost-effective way. Using the DSM and DEM, the objects height can be easily obtained. The LiDAR system also records the intensity value for each point. The intensity value can be used to generate intensity image. Extracting features from LiDAR data requires post-process to separate bare-earth points and nonground points, and then interpreting the LiDAR 3D points to grid, analysing the intensity values, identifying objects and constructing a polygon model. In this study, the methods of extracting features such as road networks, wetlands and trees from LiDAR data are presented. DEM and DSM are generated from bare-earth LiDAR points and non-ground LiDAR points. The normalized DSM (nDSM), which represents the height of objects, is obtained from DSM and DEM. The filter methods are applied for road networks extraction. Combining the DEM, countor, and intensity image, the wetland boundaries are delineated. The tree heights are obtained from the nDSM. The results show that features extracted from LiDAR data and LiDAR-derived data are more accurate. 3D features are combined with high accuracy and high resolution LiDAR derived-DEM to give a more realistic 3D environmental visualization for environment management.

Keywords: LiDAR, feature extraction, LiDAR intensity, DEM, visualization, environmental management Email: Xiaoye.Liu@arts.monash.edu.au

Geological Society of Australia Abstracts 83

Victorian Earth and Environmental Sciences Conference Monash University October, 2006

A NEW SPECIMEN OF THE SARCOPTERYGIAN FISH BARAMEDA (RHIZODONTIDA) AND HETEROCHRONY IN THE RHIZODONTID PECTORAL FIN T. M. HOLLAND^'^ ^School of Geosciences, Monash University, Victoria 3800, Australia ^Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia

The discovery of a new specinnen of the rhizodontid fish Barameda, from the Lower Carboniferous of Mansfield, Australia has provided further knowledge on hitherto poorly known aspects of rhizodontid anatomy, including information on the braincase and branchial elements. Material from this specimen has confirmed the presence of two species of Barameda in the Mansfield Group, including a large, poorly ossified species, B. decipiens, which could have reached lengths in excess of four metres, and a new species based on several smaller well-ossified specimens previously assigned to B. decipiens. Unusually, the endochondral bones of the pectoral fins assigned to B. decipiens are incompletely ossified. This includes the humeri, which lack ossified entepicondylar and pectoral processes. These processes are strong projections present on the humeri of most sarcopterygian fish and tetrapods. Juveniles of the rhizodontid Sauripterus and the tristichopterid Eusthenopteron also lack these processes (ossifying later in development), which along with poor overall ossification of the fin in juveniles and in 8. decipiens, indicates that the pectoral fin of the latter has been affected by heterochronic processes. These observations suggest a degree of developmental variability (timing, degree of ossification) in the entepicondyle relative to the rest of the humerus, which could be extended to other posterior processes of pectoral fin elements such as the postaxial flange on the ulnare. This flange is present in tristichopterids but absent in rhizodontids and elpistostegalids, such as Panderichthys and mtaalik, which are closely associated with the origin of tetrapods.

Keywords: Pectoral fin, Mansfield, Carboniferous, Rhizdontida, Barameda, heterochrony Email: tholland@museum.vic.gov.au