Geological Society of Australia
ABSTRACTS Number 75
18th Victorian Universities Earth and Environmental Sciences Conference Latrobe University 27 September 2004
Geological Society of Australia
ABSTRACTS Number 75
VUEESC Victorian Universities Earth & Environmental Sciences Conference
2004 LA TROBE lu N IVERSITY
18th Victorian Universities Earth & Environmental Sciences Conference: A meetiag organised by the Earth & Environmental Science students of La Trobe University 27 September 2004 Editor: Susan White
Latrobe University 27 September 2004
Geological Society of Australia Abstracts Number 75
18th Victorian Earth and Environmental Sciences Conference Editor: Susan White
ISSN 0729 011X © Geological Society of Australia Incorporated, 2001
Preferred citation for this volume: White, Susan (editor). 18th Victorian Universities Earth and Environmental Conference, September 2004, Geological Society of Australia Abstracts No 75, 46p
Example citation for papers in this volume White, Susan & Webb John, 2004. Karst Development at Naracoorte, South Australia: When? Why ? & How ? In White, Susan (editor). 18th Victorian Universities Earth and Environmental Conference, September 2004,, Geological Society of Australia Abstracts No. 75, p 45.
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 Printed by: Campus graphics, La Trobe University, Bundoora 3068 Victoria
VUEESC Victorian Universities Earth & Environmental Sciences Conference FORWARD I would like to welcome you to the 18th Victorian Universities Environmental and Earth Sciences Conference. The VUEESC provides an important platform for honours and postgraduate students to present their research in a professional environment. The conference is a valuable opportunity for students, academic staff and industry representatives to be updated on current research areas at a range of Victorian and interstate universities, including the University of Tasmania, University of Adelaide and the Australian National University.
This year the theme of the conference has been broadened to incorporate the physical environmental sciences. This has been done to strengthen the relationships between the environmental and earth sciences, and to emphasise the areas in which these two disciplines can successfully work alongside one another. The papers presented at the conference have been selected to cover a range of research areas and give an indication of the variety of the research currently being conducted in the Environmental and Earth Sciences field. Presentation topics range from economic and structural geology, to salinity and water chemistry. The VUEESC is a student-organised event, and as a result relies on the support of academic and industry representatives. The conference would not be possible with out the ongoing support from La Trobe University, The University of Melbourne and Monash University. I would also like to thank the industry sponsors who help make the conference possible. In particular, I would also like to express my appreciation to the Geological Society of Australia for their continual support of the VUEESC.
Joni Wooilard
Geological Society Abstracts 75
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Victorian
Universities
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The Committee of the Victorian Universities Earth & Environmental Sciences Conference would like to thank the following sponsors for their kind support: Latrobe University Faculty of Science, Technology & Engineering Latrobe University Department of Environmental Science Latrobe University Earth Science
LA TROBE ^•UNIVERSITY
technology engineenng set yourself apart
Geological Society of Australia, Victoria Division
Geological Society Abstracts 75
of Australia
Victorian
Universities
Earth
& Envimental Sciences Conference, La Trobe University September, 2004
Pl>mDOME ASIA PACIFIC
Csso i
Minerals Council oi Australia VICTORIAN DIVISION
"linking industry and students" J
Geological Society Abstracts 75
of
Australia
Victorian
Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
pmd CRC University Of Melbourne School of Earth Sciences Monash University School of Geosciences
Geological Society Abstracts 75
of Australia
Victorian
Universities
Earth
& Envimental Sciences Conference, La Trobe University September, 2004
Contents SESSION ONE: ECONOMIC GEOLOGY DANIEL A. HENRY, R.J. Squire, and C.J.L. Wilson 26 Controls on High Grade Mineralisation Within the Hangingwall Reefs, Staweil, Western Victoria J. A. ROBINSON, C.J.L. Wilson and T.J. Rawling 39 Spatial Variation in Structural Style During Mineralisation within the Basalt Contact Ore Zone, Magdala Gold Mine, Western Victoria. R.G.SMITS, S.W.Beresford, and B.F. Schaefer 43 Nd Isotopic Constraints on the Genesis of the Riwaka Ni-Cu Deposit, South Island, New Zealand D. M. MCDONALD and J. A. Webb Chemical Stability of Acid Rock Drainage Treatment Sludges
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S. SANTOMARTINO and J.A. Webb 41 Estimating the Longevity of Limestone Drains for the Treatment of Acid Mine Drainage
SESSION TWO: LITHOLOGY, STRATIGRAPHY AND MAPPING B.M. KINNA Stratigraphy of the Cenozoic Carbonates on the North West Shelf
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LT. ROBSON, M.J. Roach and R.F. Berry Lithological Mapping in a Vegetated Environment Using Aster & Geophysical Data
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STEPHEN MORAN 34 Lithological Mappping and Geotechnical Survey of Kintore Open Pit Broken Hill, NSW KATE BROMFIELD 17 Jurassic Palaeoenvironmental Reconstruction Using Plants Found at Lune River, South East Tasmania A.N. BEAR and R.A.F. Gas 14 Complex Fades Architecture and Emplacement Origins of a Mid-Miocene Mega PillowPillow Lava Sequence, Muriwai, N.Z.
Geological Society Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
SESSION THREE: STRUCTURAL GEOLOGY J.M. GREWAR, CJ.L. Wilson, R. Squire, R. IVIusgrave, and A. Dugdale. 23 The Structural, Alteration and Palaeomagnetic Variations Related to the Kewell Prospect G.R. HAIVISON The Structural Evolution Of The Lolotoi and Aileu Formations, East Timor
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M.N. BURDETT., Hand, M., & l\/1aidment, D.W. 18 Investigating Syn-Rift Melting In a Hot Intracratonic Basin: Basin Analysis with a Difference LD.LEADER 31 Modelling of the Mesoscopic and Macroscopic Structures along an East - West Transect across the StArnaud Group, Victoria. IVIEGHAN S. MILLER Alexei Gorbatov, Brian L.N. Kennett, Robert J. Stern, Zohar Gvirtzman 33 Structure of the Subducting Pacific Late Beneath the Mariana Arc: Evidence of a Tear from PWave Tomography
SESSION FOUR: SALINITY E.A. CARRARA, T.R. Weaver and I. Cartwright 20 Improved Groundwater Management Using Groundwater Geochemistry and Residence Times in the Bland Basin, NSW M.D. EDWARDS and J.A. Webb 21 Groundwater Salinity Distribution in the Tertiary Sand Aquifer of the Mount William Creek Catchment, Upper Wimmera Region, Western Victoria. B. PETRIDES, I. Cartwright, and T.R. Weaver 35 The Evolution of Groundwater in the Tyrrell Region, South-Central Murray Basin, Victoria, Australia T K. AL-HOSNI and T R. Weaver Groundwater Flow and Chemistry in the Murray Valley, Murray Basin, Australia
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E.C.IRVINE, J.F. Costelloe, A.L. Herczeg and A.W. Western Natural Salinisation Processes in Arid-Zone Environments, Central Australia.
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DARREN A. BENNETTS, John A. Webb, Malcolm McCaskill, and Reto Zollinger 15 Detailed Study of Dryland Salinity Processes In The Discharge Zone of a Local Groundwater System, Southwest Victoria A. L. BUSH 19 Controls On Groundwater Flow And Chemistry In The Springhurst Area, North East Victoria, Australia.
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M. RAIBERand J.A. Webb 38 Salt Lakes and Their Influence on the Salinity of Surface Waters in Mount Emu Creek and Fiery/Salt Creek, Western Victoria
SESSION FIVE: ENVIRONMENT AND GROUNDWATER M.E. BORMANN 16 Temporal And Spatial Trends In Rainwater Chemistry Across Central and Western Victoria. VAUGHAN BARRAS, I.Simmonds and D.Etheridge 13 An Investigation Of Moisture Transport Across South-Eastern Australia Using Stable Isotopes In Precipitation AMY PRENDERGAST The Victorian Mallee: Geomorphology Evolution
Stratigraphy
Geochronology and
37 Environmental
AMGAD ELMAHDI, Hector Malano and Shahbaz Khan Sustainability Indicator for the Coleambally Irrigation System
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ERNEST, MP. and Webb, J.A. Hydrogeology And Hydrochemistry of the Lake Boiac Area, Western Victoria
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SAMANTHA GROVER The Origin of Dried Peat Soils in the Australian Alps
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TD LAWTON Groundwater Conduits Effecting an Urban Stream North of Melbourne
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SUSAN WHITE and John Webb Karst Development at Naracoorte, South Australia: When? Why? & How?
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SESSION SIX: PALAEONTOLOGY K. J. PIPER 36 Unusual Morphological Features in Fossil Marsupials from the Early Pleistocene of Victoria D.A. SHEAN The Fauna of the Buchan Caves, South East Victoria.
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BRENT SOUTAR 44 Palaeoenvironmental Interpretation of the Whalers Bluff Formation, Portland, South-West Victoria through the Analysis Of Extant Ostracoda And Benthic Foraminifera.
Geological Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
Programme 9-9.15
Conference opened by the Dean of Science, Technology and Engineering
9.15-10.15
Session 1: Economic Geology
9.15-9.30
Daniel Henry
Controls on high grade mineralisation within the hangingwall reefs, Stawell, Western Victoria. 9.30 - 9.45
Jamie Robinson
Spatial variation in structural style during mineralisation within the Basalt Contact Ore Zone, Magdala Gold Mine, Western Victoria 9.45 - 10.00
Russell Smits
Nd isotopic constraints on the genesis of the Riwaka Ni-Cu deposit. South Island, New Zealand 10.00-10.15
Danny McDonald
Chemical stability of acid rock drainage treatment sludges 10.15-10.30
Short Break
10.30 - 11.30
Session 2: Lithology, Stratigraphy and IVIapping
10.30 - 10.45
Belinda Kinna
Stratigraphy on the Cenozoic carbonates on the North West Shelf 10.45 - 11.00
Stephen Moran
Lithological Mapping and Geotechnical Surveyof Kintore Open Pit Broken Hill, NSW 11.00-11.15
Lee Robson
Lithological Mapping in a vegetated environment using aster & Geophysical data 11.15-11.30
Kate Bromfield
Jurassic palaeoenvironmental reconstruction using plants found at Lune River, south east Tasmania 11.30 - 12.00
Morning Tea
12.00 -1.00
Session 3: Structural Geology
12.00-12.15
Julia Grewar
The structural, alteration and palaeomagnetic variations related to the Kewell Prospect 12.15-12.30
Gill Hamson
The structural evolution of the Lolotoi and Aileu formations. East Timor 12.30-12.45
MarkBurdett
Investigating syn-rift melting in a hot intracratonic basin: basin analysis with a difference 12.45 - 1.00
Lawrence Leader
Modelling of the Mesoscopic and Macroscopic Structures along an East - West Transect across the St Arnaud Group, Victoria. 1.00 - 2.00
Lunch and Posters
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Geological Society Abstracts 75
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Programme (continued) 2.00 - 2.30
Posters and Authors
2.30 - 3.45
Session 4: Salinity
2.30 - 2.45
Elisabetta Carrara
Improved groundwater management using groundwater geochemistry and residence times in the Bland Basin, NSW 2.45 - 3.00
Matt Edwards
Groundwater salinity distribution in the tertiary sand aquifer of the Mount William Creek Catchment, Upper Wimmera Region, Western Victoria 3.00-3.15
BenPetrides
The evolution of groundwater in the Tyrrell Region, South-Central Murray Basin, Victoria, Australia 3.15-3.30
TalaAI-Hosni
Groundwater flow and chemistry in the Murray Valley, Murray Basin, Australia 3.30 - 3.45
Liz Irvine
Natural salinisation processes in arid-zone environments. Central Australia 3.45 - 4.15
Afternoon Tea
4.15 - 5.15
Session 3: Environment and Groundwater
4.15-4.30
Meredith Borman
Temporal and spatial trends in rainwater chemistry across Central and Western Victoria 4.30 - 4.45
Vaughan Barras
An investigation of moisture transport across South-Eastern Australia using stable isotopes in precipitation 4.45 - 5.00
Amy Prendergast
The Victorian Mallee: geomorphology, stratigraphy, geochronology and environmental evolution 5.00 - 5.15
Amgad Elmahdi
Sustainability Indicator for the Coleambally Irrigation System 5.15 - 5.45
Posters and drinks
5.45 - 6.15
Awards, close and drinks
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Geological Abstracts 75
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GROUNDWATER FLOW AND CHEMISTRY IN THE MURRAY VALLEY, MURRAY BASIN, AUSTRALIA T. K. AL-HOSNI and T. R. Weaver School of Earth Sciences, University of Melbourne, Parkville, Vic. 3010, Australia
Physical hydrogeology in combination with water chemistry and stable isotope data have allowed a thorough understanding of the hydrogeology of the Murray Valley region of the Murray Basin. Depth to groundwater is typically 10-33 m in the east and 0.5-8 m in the west and flow directions in the Shepparton, Calivil and Renmark aquifers are generally from southeast to northwest. Lateral hydraulic gradients are very low in all the aquifers (typically <0.001) and decline towards the west-northwest. Vertical hydraulic gradients indicate potential for upward leakage from the Calivil Formation and Renmark Group to the Shepparton Formation in the west. Groundwater salinity is about 70-43,300 (S/cm, 291-55,100 (S/cm and 606-48,200 (S/cm for the Shepparton, Calivil and Renmark aquifers, respectively, and generally increases westwards. Physical hydrogeology and salinity show that recharge to the aquifers occur in the southeast via rainfall infiltration and probably flow from Victoria deep-leads across the Murray River, while discharge occurs mainly in the west. CI/Br ratios (molar 500-1000) are roughly constant with increasing salinity due primarily to evaporation during rainfall infiltration. Halite dissolution must be minor or CI/Br ratios will increase with increasing salinity. Stable isotope data also show that the evaporation is more evident in the shallow aquifers and in the discharge areas, while groundwater of the Calivil and Renmark aquifers have experienced less evaporation. The role of irrigation against the development of groundwater chemistry and current heads and the bedrock control on flow paths are not yet established and will need further investigations. The results of this study will have implications for the development and management of salinity and sustainability of groundwater in this area.
Keywords: Murray Basin, groundwater chemistry, stable isotopes, salinity, evaporation Email: t.al-hosni@pgrad.unimelb.edu.au
Geological Society Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
AN INVESTIGATION OF MOISTURE TRANSPORT ACROSS SOUTHEASTERN AUSTRALIA USING STABLE ISOTOPES IN PRECIPITATION V. BARRAS\ 1. Simmonds^ and D. Etheridge^
^School of Earth Sciences, University of Melbourne, Parkville, Victoria, Australia 2 CSIRO Atnnospheric Research, Aspendale, Victoria, Australia
Measurements of the relative abundance of the naturally occurring isotopes and deuterium (D) in precipitation are a valuable resource in the study of atmospheric moisture processes and climate variability. Fractionation of these isotopes occurs during changes of phase of natural water as it passes through the hydrological cycle (such as evaporation from an oceanic surface or condensation during cloud formation). This process preserves information about the history of the air mass. There are, however, many environmental effects that can modify the fractionation of and D (reported as a relative depletion against a known standard); therefore it is imperative to understand the extent of these influences in order to accurately interpret variability in the isotopic record preserved in precipitation and in ice-cores. Preliminary investigation has focussed upon moisture transport across southeastern Australia using measurements of in precipitation taken on a case by case basis at two locations in Tasmania, Margate and Cape Grim. After having filtered the data to account for seasonal fluctuations and rainfall amounts, composite Mean Sea Level Pressure anomalies have revealed characteristic atmospheric circulation features of the most isotopically depleted rainfall events when compared to events of least isotopic depletion. In addition, three day backward trajectories have been run using the Margate rainfall observations coupled with 850hPa wind data from the ECMWF 40 year reanalysis in order to identify potential source regions for moisture being transported across southeastern Australia. In both cases of greatest and least isotopic depletion, there is a significant remote moisture source located in the Southern Ocean, and indication of the dominance of the zonal westerlies across Tasmania. Results from this analysis also show interesting differences in the locations of the more proximal moisture source regions. Investigation using measurements of in precipitation has revealed an apparent link between the extent of isotopic depletion and their association with particular synoptic circulations. Another avenue of investigation has been the establishment of the Melbourne University Network of Isotopes in Precipitation (MUNIP). This is a network of observation sites located around Port Phillip Bay sampling rainfall half hourly, with the aim of recording the spatial and temporal variability of and D during the passage of significant rainfall events. Measuring the isotopic signal in this way can identify in cloud physical processes as well as provide information upon the influence of local moisture sources. Early results have been promising, and there is an increasing interest in the results from the full MUNIP network.
Keywords: Isotopes, precipitation, trajectories, moisture sources. Email: vbarras@earthsci.unimelb.edu.au
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Geological Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
COMPLEX FACIES ARCHITECTURE AND EMPLACEMENT ORIGINS OF A MID-MIOCENE MEGA PILLOW-PILLOW LAVA SEQUENCE, MURIWAI, N.Z. A.N. BEAR and R.A.R Cas School of Geosciences, Monash University, Australia, 3800.
Spectacular mega pillow-pillow lava sequences occur in coastal exposures at Muriwai, New Zealand. The exposure at Maori Bay reveals a complex association of basaltic andesitic volcanic fades, including massive columnar jointed units, lava feeder tubes, mega pillow-pillow lavas, massive sheet flow lobes, hyaloclastite and peperite. The sequence was emplaced, in part at least, as an invasive lava flow, which burrowed into the unconsolidated sediment on the sea floor producing hyaloclastite and peperitic textures at the margins of the pillows. Two massive sheet flow lavas, which appear at the base of the northern lava tube feeder and at the top of the southern lava tube feeder are characterised by colonnade columnar jointing. They were both emplaced as result of higher magma effusion rate. A second exposure at Collins Bay, extending south to Pillow Lava Bay, exhibits more crystal rich mega pillow lavas, which are basaltic in composition. The two exposures collectively form the Maori Bay Member Volcanic Succession (M.B.M.V.S). Sedimentary fades associated with the M.B.M.V.S indicate emplacement occurred in a volcaniclastic apron setting on the subaqueous slope of a marine stratocone, which formed one of a chain of island stratocones within the Waitakere Volcanic Arc.
Email: anbear70@hotmail.com
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Geological Society Abstracts 75
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Australia
Victorian
Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
DETAILED STUDY OF DRYLAND SALINITY PROCESSES IN THE DISCHARGE ZONE OF A LOCAL GROUNDWATER SYSTEM, SOUTHWEST VICTORIA DARREN A. BENNETTS\ John A. Webb\ Malcolm McCaskilP ^ and Reto Zollinger^ ^ Departnnent of Earth Sciences, La Trobe University, Bundoora, VIC, 3086, Australia
The geology, hydrogeology and hydrochemistry of a groundwater discharge zone and associated recharge zone on 34 hectares of saline land near Dunkeld was characterised using data from a high-density network of peiozometers (two per hectare), 40 intact soil cores and eight soil pits. The site forms part of the national network of Sustainable Grazing on Saline Lands (SGSL) study sites. The study showed that the most important requirement for the development of salinisation in the groundwater discharge zone is a shallow watertable (1-2 m from the surface). Direct evaporation at the watertable, particularly in summer, concentrates salts contained within the groundwater, leading to extremely high soil-water salinities at the surface, even if the underlying groundwater is moderately fresh. At the Dunkeld site the watertable beneath the discharge zone remains close to the surface all year and evaporation is intense. However if the water table reaches the surface during the winter months but is well below the surface in summer, the salinity threat is lower, because the groundwater is not exposed to evaporation during summer. Other mechanisms are often proposed to explain secondary salinisation in groundwater discharge zones, including saline groundwater coming to the surface and dissolution of salt stores within the sediments by rising groundwater. Neither of these is a major contributor to salinisation at Dunkeld, as the underlying groundwater is quite fresh and the soil-water salt concentrations below the surface at the discharge zone are low. Sediment permeability also plays a major role in acquiring and retaining salt. The highest salt concentrations are in the lowest permeability clay-rich sediments. The low hydraulic conductivity of these sediments increases the time water moving through them is exposed to evaporation and reduces the potential for salts to be flushed from the sediments. The groundwater discharge zone at the Dunkeld site occurs at a break in slope, partly because this is where the sloping watertable intersects the surface. In addition, this is where finer, more clay-rich sediments with lower permeability inhibit lateral groundwater flow and force it upward to the surface.
Keywords: Salinity, evaporation, hydrochemistry Email: D.Bennetts@latrobe.edu.au
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TEMPORAL AND SPATIAL TRENDS IN RAINWATER CHEMISTRY ACROSS CENTRAL AND WESTERN VICTORIA. M.E. BORMANN La Trobe University, Bundoora, Australia
Rainfall samples were collected monthly over a 12 month period (September 2003 - August 2004) from 14 manually operated weather stations throughout western and central Victoria. Samples were analysed Na\ Ca/, K^ HCO^", CI", SO/- and Br in order to identify the relative influence of seawater aerosols and airborne particulate matter (primarily dusts) to the chemistry of the rainwater, and the variations observed both temporally and spatially. Trends in total dissolved solids (TDS), pH, alkalinity (HCO3-) and ion concentrations are evident, and can be interpreted in terms of the relative influence of the different ion sources on the chemistry of rainwater. TDS (as mg/L) is higher during the summer months compared to the winter months, reflecting the greater levels of all major ions analysed. In general rainwater pH is higher in summer than in winter, and both HC03- and Ca^"^ concentrations show a similar trend and are strongly correlated with each other. There is a definite decrease in Ch concentration with increasing distance inland, as noted in many previous studies. Na+ concentrations closely follow those of C|- so the trends observed for the two ions are similar. HCO^- and pH typically increase with distance inland. Values for the Na/CI ratio remain fairly constant across the state, whereas ratios of Ca/CI and HCO^ /CI increase with increasing distance inland. These ratios confirm that the sources of Gl and Na+ in the rainwater are primarily salt spray from the oceans, whereas the C a / and HCO^" ions are sourced predominantly from dust at inland locations. There is a poor correlation between TDS and rainfall volume, indicating that rainfall volume alone does not control the ion concentrations detected in rainwater. Rather, the data seems to indicate that seasonal variation in wind intensity, which determines the amount of terrestrial dust input to the atmosphere, may have a controlling influence on the temporal variation in rainfall composition.
Keywords: Rainwater, hydrochemistry. Email: mebormann@hotmail.com
Geological Society Abstracts 75
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Australia
Victorian
Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
JURASSIC PALAEOENVIRONMENTAL RECONSTRUCTION USING PLANTS FOUND AT LUNE RIVER, SOUTH EAST TASMANIA KATE BROMFIELD University of Tasnnania
Jurassic plants excavated from a 12 by 5 m site, at Lune River, southern-most Tasmania, contain an Araucarian tree and numerous pteridophytes, belonging to the orders Osmundales, Filicales and Bennetitales. Deposition occurred in an aqueous, probably lacustrine environment, where the plants had undergone variable degrees of decomposition prior to burial. Stems of the fossil pteridophytes are in a non-life position, oriented southeast with an average dip of 40° indicating that a unidirectional force acted on them during deposition. The fossils are buried within sequential immature volcanilithic, sandstone beds, approximately 1 m thick. The sandstone primarily consists of clasts from granitic basement rocks, mafic clasts containing feldspathic microlathes, and primary, phreatomagmatic quartz crystals. Zircons from the units show a Permo-Triassic age distribution, with the majority returning an age of 182+/- 4 Ma. Siliceous ground water fluids silicified both the fossils and the volcanilithic units. Jurassic basalt (MgO 5.4-5.6 wt %, Si02 55.1-55.5-wt %) caps the volcanilithic units. Both display very similar ratios of fluid-immobile trace elements (eg, Zr/Nb, TiA/ and ZrA^), indicative of a common source. However, the sandstone has much higher K20 and TiA/, due to weathering and ground water movement. The basalts are correlated with the extensive Tasmanian Jurassic dolerite and the Kirkpatrick Basalts (Trans-Antarctic Mountains, Antarctica) based on their field relationships with bounding strata, age, and distinctive similarities in major element composition and fluid-immobile trace element ratios. The basalt is interpreted as an extrusive equivalent of the Tasmanian dolerite, and field evidence indicates that the basalt predates the dolerite at Lune River. Based on comparative morphology of the plants, the sedimentology and stratigraphy of the depositional environment plus hydrophilic pteridophytes and gymnosperms with unusually large tracheids, 40 m across, and wide growth rings, 1-2 cm, the Toarcian/ Pleinsbachian environment, at 75-82° south, was warm and humid with an abundant supply of water. Lune River itself was the location of a wide lake.
Keywords: palaeoenvironment, Jurassic, plants, basalt, Tasmania, lacustrine Email: bromfiek@utas.edu.au
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INVESTIGATING SYN-RIFT MELTING IN A HOT INTRACRATONIC BASIN: BASIN ANALYSIS WITH A DIFFERENCE BURDETT, M.N., Hand, M., & Maidment, D.W., 2004 University of Adelaide
The recent interpretation that the Harts Range Metamorphic Complex in the southeastern Arunta Region, central Australia contains a metamorphosed >25km intracratonic rift system has challenged our understanding of the way deep sedimentary basins develop. A review of comparative studies of more recent >25km deep sedimentary basins indicate that such deep basins have common features i.e.: locations of formation on passive continental plate margins, structural styles and, lithospheric conditions, and their formation defines a continuum of the global strain rate trend. The increasing recognition of the fundamental role of lithospheric processes in the development of sedimentary rift-basins has lead to the realisation that there are suites of extensional styles formed by individual lithospheric conditions. Recent zircon provenance studies of protoliths to the Harts Range Metamorphic Complex have concluded the Irindina Province located within the Harts Range Metamorphic Complex is a highly metamorphosed rift sequence deposited in a sub-basin to the Neoproterozoic Centralian Superbasin. The sub-basins formation is analogous with modern examples of deep sub-basins having developed on the early Palaeozoic passive margin of Gondwana during NE orientated extension. This period of extension was broadly coeval with extension in the Canning Basin NW Western Australia, in the Adelaide Rift Complex South Australia and Anakie Inlier NE Queensland. This suggests that its development was to some extent part of a larger extensional system active during this period. Recent dating, geochemical and isotopic analysis of syn-rift granites formed via partial melting of the basal units of the Irindina Province in the Harts Range Metamorphic Complex rift sequence has allowed the opportunity to constrain sedimentation rates and thermal conditions within the high-grade palaeo-rift system. By correlating the crystallisation age of the granite and the age of deposition for younger, lower grade sediments within the rift sequence a rate of sedimentary deposition for the basin can be inferred. The analysis of conditions during generation of granites in the Irindina Province rift system can provide constraints on the thermal regime in the deepest parts of an active rift. It also suggests that the anatexis of high-grade rocks is not exclusive related to convergent processes
Emaihmark.n.burdett@student.adelaide.edu.au
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Geological Society Abstracts 75
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Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
CONTROLS ON GROUNDWATER FLOW AND CHEMISTRY IN THE SPRINGHURST AREA, NORTH EAST VICTORIA, AUSTRALIA. A. L BUSH School of Earth Sciences, University of Melbourne, Parkville, Vic. 3010 Australia
A groundwater observation bore network in Springhurst, North East Victoria, Australia was analysed for groundwater flow, geochemistry, and stable isotopes 8 ^^C, 8 ^H and 8 In addition, five 1m soil profiles were drilled in the area and analysed for moisture and major anions. The Springhurst area has a semi-arid Mediterranean climate and has been cleared of most native vegetation for cattle and sheep grazing. The groundwater development is negligible. The physical analysis showed that the groundwater of the Springhurst region flows predominantly from east to west through several heterogeneous geological units and that there is a semi-confined unit within the fractured Ordovician sandstone. Discharge areas are controlled by topography, occurring in gullies; and geology, occurring at the break of slope boundary between fractured basement rock and Murray Basin alluvial sediments. Evapotranspiration dominates in these areas to concentrate the salt in the soil and groundwater at the surface. The electrical conductivity of the groundwater ranges from 1,000 - 20,000 piS/cm. Groundwater level fluctuations and stable isotope results confirm the processes of winter recharge and summer evapotranspiration. The hydrogeochemistry reveals that the water is dominated by sodium and chloride sourced from marine aerosols in precipitation. Aeolian deposition of sulphate from continental dust is also substantiated by water and soil geochemistry. Sodium, bicarbonate, silica and magnesium have been enriched in certain samples due to water-rock interaction. CI/ Br ratios in soil and groundwater imply that a small amount of localised halite dissolution occurs close to the surface. The results of this study illustrate the controls on a local hydrological system which affect the development of salt patches, especially in discharge zones. This system is shown to be vulnerable to the effects of climatic changes. However, response to remediation measures such as revegetation with salt tolerant species has been observed.
Keywords: Hydrogeology, North East Victoria, salinity, geochemistry, stable isotopes, water-rock interaction. Email: albush@pgrad.unimelb.edu.au
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Geological Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
IMPROVED GROUNDWATER MANAGEMENT USING GROUNDWATER GEOCHEMISTRY AND RESIDENCE TIMES IN THE BLAND BASIN, NSW
E.A. CARRARA^ T.R, Weaver^ and L Cartwright^ ^ School of Earth Sciences, University of Melbourne, Parkville, Vic. 3010, Australia 2 School of Geosciences, Monash University, Clayton, Vic. 3800, Australia
Multi-component geochemical tracers together with physical parameters were used to identify the processes controlling groundwater chemistry and flow in the Bland Basin, NSW. These data were combined with groundwater residence times determined from ^^C dating to provide a better understanding of the hydrogeological system for improved groundwater management. The dominant hydrogeological units in the basin are Tertiary alluvial deposits in the buried Lachlan and Bland paleovalleys. These are the most important sources of groundwater. The Miocene to Pliocene Lachlan Formation occupies the base of the paleovalleys, whereas the less permeable Pleistocene Cowra Formation occupies the upper, wider portion of the paleovalleys. In the Bland Basin, groundwater in the Lachlan Formation is fresher (EC<5000 (S/cm) than in the more heterogeneous Cowra Formation (EC 741-48400 (S/cm). Groundwater in the Lachlan palaeovalley has much lower ECs (max 1573 (S/cm). Na/CI ratios in groundwater range from 0.5 to 8.14. The variable Na content indicates minor water-rock interaction, mainly localised in the Lachlan Valley and in the eastern area of the Bland Basin. CI/Br molar ratios throughout the study area range from 400 to 760, thereby excluding halite dissolution. 36CI, the stable isotope data, and CI/Br ratios all indicate that evaporation is an important process leading to the buildup of salinity in the Bland aquifers. Radiocarbon dating in both Cowra and Lachlan Formations indicates recently-recharged (bomb pulse) groundwater only occurs in the east of the Bland Basin. Although the reversal in groundwater flow directions has been attributed to irrigation in the northern Bland and Lachlan Valleys, groundwater residence times indicate that this is related to a much older process. Future management of groundwater should consider that modern recharge in the Bland Basin is limited and that groundwater discharge from the Bland into the Lachlan is likely to be limited.
Keywords: Groundwater, 14C, 36CI, salinity. Email: e.carrara@pgrad.unimelb.edu.au
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Geological Society Abstracts 75
of Australia
Victorian
Universities
Earth
& Envimental Sciences Conference, La Trobe University September, 2004
GROUNDWATER SALINITY DISTRIBUTION IN THE TERTIARY SAND AQUIFER OF THE MOUNT WILLIAM CREEK CATCHMENT, UPPER WIMMERA REGION, WESTERN VICTORIA. M.D. EDWARDS and J.A. Webb Department of Earth Sciences, LaTrobe University, Bundoora, Australia
The Mount William Creek catchment is located in the upper reaches of the greater Wimmera River catchment in western Victoria. The area is bounded to the west by the ranges of the Grampians-Geriwerd National Park and to the south and east by the Great Dividing Range and the Ararat Hills. Groundwater chemistry data from the Tertiary sand aquifer (Calivil Formation equivalent) show a steady decrease in Total Dissolved Solids (TDS) down flow-path. In the headwaters of the catchment, downward hydraulic gradients drive moderately saline groundwaters (30004000 jxs/cm) from the overlying Shepparton Formation into the underlying sands, causing salinisation of the lower aquifer 3000 ^is/cm). However, as groundwater in the Tertiary sand moves down-flow it becomes less, rather than more saline (< 1000 \xs/crr\). This is due to the upwelling of fresher waters from the Palaeozoic basement (Glenthomson Sandstone and Grampians Group). This upwelling is driven, at least in part, by a prominent Cambrian greenstone belt that acts as a permeability barrier within the basement, because salinities west of the greenstone, and adjacent to the Grampians, are significantly less saline than groundwater immediately east of the belt. This greenstone unit frequently forms prominent outcrops along strike, and is visible as a continuous feature in airborne magnetics imagery. Where the greenstone outcrops, it divides the catchment into two palaeovalleys; the degree of interconnection between these, in areas with no greenstone outcrop, is poorly constrained. At the down-flow end of the catchment, groundwaters in the Tertiary sand aquifer, and in the overlying Shepparton Formation, must pass through a narrow bottleneck formed by basement units, before flowing out into the Wimmera Plains. This induces shallow watertables and land salinisation of the area west of Lake Lonsdale and may be partly responsible for occurrences further upstream.
Keywords: salinity, Mount William Creek, Wimmera, Calivil Formation, greenstone belt. Email: Matthew.Edwards@latrobe.edu.au
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HYDROGEOLOGY AND HYDROCHEMISTRY OF THE LAKE BOLAC AREA, WESTERN VICTORIA ERNEST, M.R & Webb, J.A. Department of Earth Sciences, La Trobe University, Bundoora 3083, VIC, Australia
The township of Lake Bolac is situated in southwestern Victoria approximately 100 kilometers west of Ballarat. Directly to the northwest of the township, lakes Paracelmic and Gentine are part of a natural salt lake system that has been present for centuries. Community groups have been concerned about rising water levels and the growing effects of salinity around the town and its impact on town planning, infrastructure, and social, recreational and economic activities. In order to fully understand the issue and plan appropriate mitigation efforts for the future, research was undertaken on the ground and surface hydrology of the area. A detailed hydrochemical study, incorporating major element analysis was conducted at 36 sample sites across the area, selected to include groundwater monitoring bores and surface water locations. Bore logs, along with airborne radiometrics and magnetics show that the area consists of three major geological units: Quaternary basalts, Tertiary sands and Palaeozoic bedrock. The geology of the area is complicated by the Moyston and Woorndoo faults, which interstect Lake Bolac and possibly Lakes Paracelmic-Gentine respectively. Both Lakes Paracelmic and Gentine lie in a topographic low that focuses local groundwater flow within the basalt aquifer, so salt accumulation within the lakes is the result of evaporative processes in a groundwater sink. The rising salinity levels within freshwater Lake Bolac had been proposed to be due to leakage of saline water from Lakes Gentine and Paracelmic, but bore data collected during this project has discounted this, because the water level in Lake Bolac sits topographically higher than the salt lakes. The causes of lake expansion and possible mitigation of the problem will be investigated further.
Key Words: Hydrogeology, Hydrochemistry, Lake Bolac, Lake Gentine, Lake Paracelmic.
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Geological Society Abstracts 75
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Australia
Victorian
Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
THE STRUCTURAL, ALTERATION AND PALAEOMAGNETIC VARIATIONS RELATED TO THE KEWELL PROSPECT J.M. GREWAR\ C J . L Wilson\ R. Squirel, R. MusgraveS and A, Dugdale ^ University of Melbourne, Parkville, 3010, Australia 2 School of Geosciences Monash University
The mineralised Kewell prospect in western Victoria is hosted by rocks which display similar lithologies, structural characteristics and alteration assemblages to the world class (upper 10% of deposits in terms of contained metal.) Magdala gold deposit, located about 100 km to the south-southeast. Despite the broad similarities, the nature of the basalt body and surrounding sediments is poorly understood, the extent of alteration zonation and assemblages are currently undefined, and the factors controlling the magnetic anomaly are unknown. The research attempted to correlate the structural fabrics, rock magnetic data and alteration fades across the Kewell basalt body, in order to gain an insight into features controlling mineralisation within the Stawell-Kewell Belt. The volcanic facies at Kewell is the lower most stratigraphic unit and consists of basalt (massive, pillowed and hyaloclastite). Clastic sedimentary units consist of laminated mudstone and fine grained sandstone. Importantly, there is no fine grained sandstone on the western side of the basalt body, indicating that the succession is not folded. Intercalated with the main sedimentary units are rarer sulphidic mudstone intervals in association with deformed chert bands, and calcareous siltstone units. The lithologies exhibited similar ductile and brittle fabrics. The rocks have undergone regional metamorphism, in addition to multiple hydrothermal alteration events related to mineralisation. A rock magnetic analysis was completed to define the factors controlling the magnetic anomaly. Remanent magnetisation contributes to the negative parts of the anomaly, however directions of magnetisations remain unclear. Either viscous remanent magnetisation (VRM) or induction contribute to the positive component of the anomaly.
Keywords: Mineralisation, magnetic anomaly, hydrothermal alteration Email: jgrewar@ugrad.unimelb.edu.au
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Geological Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
THE ORIGIN OF DRIED PEAT SOILS IN THE AUSTRALIAN ALPS SAMANTHAGROVER
Peat bogs in the Australian Alps have long been considered important in catchment hydrology (Costin 1952) and, at 1-5m deep and 80-100% organic matter, comprise substantial carbon stores. Bogs form where cold, wet conditions inhibit organic matter decomposition, occurring in valley bottoms and below springs and seepages. Sphagnum moss and wetland shrubs form the characteristic hummock and hollow surface topography seen in bogs world-wide. Rootless, Sphagnum is susceptible to erosion if the soft surface is damaged by trampling. Dried peat, a shallow (<0.5m) organic soil extensive throughout the Alps, is commonly found adjacent to Sphagnum bogs. Sphagnum bog peat was identified as the parent material of dried peat by Costin (1954). Dried peat has a number of properties similar to the properties of the lower layer of bog peat (Grover 2001). This lead to our hypothesis, that dried peat formed from the lower layer of an intact bog. An alternative explanation for the presence of dried peat on the margins of bogs is that it formed, and subsequently dried, prior to the initiation of current peat bogs. We used 13C NMR and radiocarbon dating to compare the carbon chemistry and age of dried peat and bog peat. Understanding where dried peat comes from will improve our ability to manage the Alps for optimal carbon storage, water yield and biodiversity.
Email: spgrover@students.latrobe.edu.au
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Geological Society Abstracts 75
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Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
THE STRUCTURAL EVOLUTION OF THE LOLOTOI AND AILEU FORMATIONS, EAST TIMOR G.R. HAMSON School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia
East Timor represents the point at which the leading edge of the Australian continental margin collided with the Eurasian plate, giving a rare insight into the early stages of a major orogenic event. Upon reaching the Eurasian Arc, buoyant Australian continental lithosphere jammed northward subduction during the Neogene, resulting in arc-continent collision. Detailed structural mapping in East Timor was undertaken in May-June 2004, focusing upon two main metamorphic massifs, the Lolotoi Formation (central East Timor) and the Aileu Formation (northwestern East Timor). In addition, twenty-two samples were collected for apatite (U-Th)/He analysis. The apatite (U-Th)/He thermochronometer, with a low closure temperature of 65-75°C, allows us to constrain active surface processes and exhumation conditions across a deforming region. The Lolotoi Formation is a greenschist-grade metamorphic package of interlayered metasediments and volcanogenics. Two structural fabrics were observed: a pervasive, flat-lying S1 foliation with indications of layer-parallel shear, and a steeply-dipping localised S2 crenulation cleavage. No macrostructures were seen to be associated with these fabrics. A late brittle faulting event affected the macroscopic structure of the region, faulting the Permian Lolotoi Formation against the Miocene Cablac limestone. The Aileu Formation comprises metamorphosed sediments which range from greenschist to upper amphibolite grade. A pervasive, progressive layer-parallel fabric (S1) is indicative of bulk shortening, later transposed by a south directed S2 fabric associated with regional shear zones. Relicts of the original north-directed deformation, evidenced by top-to-the-north thrust planes and duplex geometries are observed between south-directed shear zones. It is proposed here that the Aileu Formation is the oceanic basement of the pre-collisional forearc, while the Lolotoi Formation is the sedimentary/magmatic cover of that forearc basement. Both were emplaced in a southward direction above the autochthonous Australian margin.
Keywords: East Timor, tectonics, structure, arc-continent collision, apatite U-Th/He analysis. Email: g.hamson@ugrad.unimelb.edu.au
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Geological Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
CONTROLS ON HIGH GRADE MINERALISATION WITHIN THE HANGINGWALL REEFS, STAWELL, WESTERN VICTORIA DANIEL A. HENRY, RJ. Squire, and C J . L Wilson School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia
The hangingwall reefs at Stawell are located 100-300 metres west of the Magdala Basalt and produced approximately one million ounces at grades varying from 9-30 g/t. Despite the generous endowment of these reefs there is a lack of understanding on the controls on gold lode distribution within the reefs. With the development of prospects to the north such as Wildwood and Kewell, an understanding of these hangingwall reef structures at Stawell is needed to aid in the identification of similar structures in the prospects. The aim of this project is to map out the stratigraphy and structure west of the Magdala Basalt in an attempt to gain an understanding on the controls on mineralization and come up with a model of mineralisation within the hangingwall reefs. This model can be used in the prospects to constrain where gold distribution is likely to occur along hangingwall reef style structure. There appears to be a correlation between gold distribution and the stratigraphy. West of the Magdala Basalt, five sedimentary lithofacies have been identified in the sediments. These include black mudstone, quartz-rich sandstone, siliceous siltstone, calcareous siltstone, and sulfidic black mudstone and have varying distributions. The hangingwall reef mineralization occurs predominately in the finer grained fades. The orientations and relationships between regional ductile fabrics and the Stawell Fault appear to exert a strong influence on the gold distribution in the hangingwall reefs. The hangingwall reefs exist at shallow levels along the Stawell Fault and related splays. The reefs are localized in areas where regional fabrics have obliquity to the fault on both sides, producing dilational sites. The geometry of the splays off the Stawell Fault, which are also mineralised, appears to be controlled but the orientation of regional S3.
Keywords: Stawell gold fields, Stawell Fault, gold mineralisation. Email: d.henry2@ugrad.unimelb.edu.au
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Geological Society Abstracts 75
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Earth
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Envimental Sciences Conference, La Trobe University September, 2004
SUSTAINABILITY INDICATOR FOR THE COLEAMBALLY IRRIGATION SYSTEM AMGAD ELMAHDP, Hector Malano^ and Shahbaz Khan^
^ IDTC, Civil & Environmental Engineering Department Melbourne Uniiversity 3010 Victoria-Australia. 2 CSIRO Land and Water, Griffith, 2680 NSW.
An indicator defined as a function of the total water diversion through the Coleambally canal and the potential irrigation demand is selected to represent the sustainability of the irrigation water system in the Coleambally irrigation area, Australia. A simulation procedure was developed to evaluate the indicator. The procedure includes water diversion assessment, potential crop water demand and total gross margin. Three cases of water supply options (ground water pumping and water trading), two cases of changes in the total agricultural area and three cropping pattern scenarios were simulated to better understand their impact on sustainability. The simulated results indicate that increasing the agricultural area will reduce the sustainability of the irrigation system as the demand will be more than 80 percent despite increase the gross margin. The scenarios shown that imposed water trading and ground water pumping would considerably increase the supply system having a positive impact on the sustainability. The paper concludes that a multi-objective sustainability indicator taking account of economic and environmental issues could be more useful.
Emails: A.Elmahdi@civenv.unimelb.edu.au h.malano@devtech.unimelb.edu.au shahbaz.Khan@csiro.au
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Geological Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
NATURAL SALINISATION PROCESSES IN ARIDZONE ENVIRONMENTS, CENTRAL AUSTRALIA. E.G. IRVINE^ J.R Costelloe\ A.L. Herczeg^ and A.W. Western^ ^Department of Civil and Environmental Engineering, University of Melbourne, Parkville (Vic) 3010 2CSIR0 Land and Water, Glen Osmond (SA) 5064
In the lower reaches of the Neales, Peake and Warbuton Rivers and the Coongie Lakes (Coopers Creek) of the Lake Eyre Basin (central Australia) it has been hypothesized that there are several natural processes causing the observed salinisation of local surface waters and shallow groundwaters. These processes are thought to include evapotranspiration, cyclic precipitation and dissolution of salts (namely carbonates, gypsum and halite), water-sediment interaction within the local bank and floodplain sediments, redistribution of surface salts and the mixing of shallow, local floodplain groundwaters with more regional groundwater flows. Preliminary fieldworks, including the installation of shallow piezometers and subsequent sampling of shallow groundwaters and surface waters for major ions and stable environmental isotopes indicates that in each of the study areas, evapotranspiration of recharge water appears to dominate the chemical evolution of the shallow groundwater. Groundwaters sampled are saline (13,659mg/L to 155,078mg/L total dissolved salts) with sodium-chloride-sulphate or sodium-chloride dominated compositions. Field observation of gypsum and carbonate salts within sediments, particularly in the root zone and water table capillary zone, indicate that salt dissolution and precipitation also plays a role in determining the final groundwater composition. These observations are supported by both isotopic and major ion data. Hydraulic head data, combined with salinity measurements indicates that at (semi-) permanent waterholes on the Neales and Warbuton Rivers mixing between surface waters and shallow groundwater is also occurring, ultimately influencing the waters observed compositions. Major ion and isotopic data for the Coongie Lakes suggest minimal, if any, direct interaction between the lake surface waters and local, uppermost groundwater system.
Keywords: Hydrogeology, groundwater, arid zone, natural salinity Email: lizzie@civenv.unimelb.edu.au
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Geological Society Abstracts 75
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Victorian
Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
STRATIGRAPHY OF THE CENOZOIC CARBONATES ON THE NORTH WEST SHELF B.M. KINNA School of Earth Sciences, The University of Melbourne, Victoria 3010
The North West Shelf extends 2400knns along the Western Australian margin and is divided into the following four sedimentary basins: Carnarvon, Canning, Browse, and Bonaparte. Significant quantities of carbonate were deposited on the shelf during the Cenozoic. However, these carbonates remain poorly documented with few previous studies concentrating on the stratigraphy. Using seismic properties, geochemical analysis (carbonate and elemental), well log data, and petrological data this study establishes the stratigraphic framework of the Cenozoic carbonates of the Exmouth-Barrow region. Northern Carnarvon Basin. The Cenozoic carbonate sequence represents a shallowing upwards sequence from Eocene to Middle Miocene in age. The base of the sequence is dominated by deep basinal fades, overlain by prograding Oligocene-Miocene shelf and slope sediments. These are inturn overlain by quartz-rich sediments interpreted to represent a sand barrier. A transgression during the Late Miocene-Pliocene returned the depositional environment to prograding shelf conditions.
Keywords: Carbonates, North West Shelf, stratigraphy Email: b.kinna@pgrad.unimelb.edu.au
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Geological Society Abstracts 75
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Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
GROUNDWATER CONDUITS EFFECTING AN URBAN STREAM NORTH OF MELBOURNE T.D LAWTON School of Ecology and Environment, Deakin University Burwood Hwy Melbourne, Australia
The major rock units found to the north of Melbourne contribute significant base flows to the creeks that run over them. The Silurian Dargile Formation and Pleistocene Newer Volcanics are the principal formations that underlie Darebin Creek, and the structures within these formations, as well as the boundaries between them, determine the volume of water that reaches the creek at any one point. A detailed geological survey of the Newer Volcanics along the southern section of Darebin Creek has indicated that some sections of the waterway are more likely to receive groundwater than other parts due to the nature of jointing, weathering and human modification. These differences in groundwater inflow can have implications for pollution influx especially in the more developed industrial areas. A framework for pollution risk assessment based on groundwater inflow has been developed that will allow sections of the creek to be rated according to water movement and consequently likelihood of pollution. Specific conduits for groundwater discharge in the Darebin Parklands have also been identified and examined.
Keywords: Darebin Creek, Newer Volcanics, groundwater, basalt, jointing. Email: tla@deakin.edu.au
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Geological Society Abstracts 75
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Universities
Earth
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Envimental Sciences Conference, La Trobe University September, 2004
MODELLING OF THE MESOSCOPIC AND MACROSCOPIC STRUCTURES ALONG AN EAST WEST TRANSECT ACROSS THE ST ARNAUD GROUP, VICTORIA. LD.LEADER University of Melbourne.
The StArnaud Group is a poly-deformed sequence of Cambrian-Ordovician quartz rich turbidites that outcrop within the Stawell Zone of the Lachlan Fold Belt. Structural mapping of the St Arnaud Group, conducted between Concongella Hill and the Pyrenees Ranges, has been used to interpretate the structure through the production of a regional scale cross-section. The structure of the upper crust is characterised by two major reverse faults, the Concongella and Landsborough Faults, which separate St Arnaud Group sediments that have undergone a single deformation event from StArnaud Group sediments that have undergone two deformation events. The regional scale cross section was then used as a basis for the two dimensional modelling, using GM-SYS, of gravity and magnetic data, which provided an indication of the deeper subsurface structure. The modelling results were consistent with the regional scale structure that was inferred from the structural mapping and also provided evidence of the existence of a third fault between the Landsborough and Concongella Faults. This regional scale structural interpretation was then used to construct numerical models using FLAC 2D. The aim of the numerical modelling was to identify the presence of zones of dilation, indicating areas where metamorphic and potentially mineralising fluids may have been channelled. This will allow regional scale geometrical controls on fluid flow to be identified and provide insights into the regional setting of the corridor of gold mineralisation that is recognised at Stawell.
Keywords StArnaud Group, modeling, gold mineralisation. Email: lleader@ugrad.unimelb.edu.au
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
CHEMICAL STABILITY OF ACID ROCK DRAINAGE TREATMENT SLUDGES D. M. McDonald and J. A. Webb Environmental Science, La Trobe University, Victoria 3086
Acid Rock Drainage (ARD) is widely recognised as one of the greatest environmental issues facing the mining industry worldwide. Much work has gone into preventing and treating ARD, but surprisingly little research has been conducted on the sludges formed when ARD is neutralised. Active neutralisation of ARD involves adding an alkaline reagent; the reaction causes metal hydroxides to precipitate. Lime (Ca(0H)2) is the most commonly used reagent as it is widely available and cost effective, but other reagents have been used (e.g. CaCOg, NaOH), and there are also more expensive proprietary reagents available. Treatment with lime produces an amorphous metal hydroxide sludge, often with less than 5 wt% solids. Disposal of the sludge is typically in the mine environment, but the chemical stability of the sludge under these conditions is uncertain. The aim of this project is to carry out a laboratory investigation of the chemical stability of ARD treatment sludges under conditions simulating likely disposal options, particularly leaching by low pH waters that commonly occur in mine environments. Synthetic ARD containing 1200ppm Fe, lOOppm Al, lOOppm Cu and lOOppm Zn was made up by dissolving metal sulphate salts in tap water and acidifying to pH 2.3 with H2SO4. The ARD was neutralised using lime, limestone (CaC03) and two novel proprietary products (Bauxsol and KB-1). Chemical stability of the laboratory sludges was assessed by leach testing in neutral to acid environments using two US EPA methods (TCLP, Toxicity Characteristic Leaching Procedure, method 1311, and SPLP, Synthetic Precipitation Leaching Procedure, method 1312) and a Strong Acid Leach Test (SALT). SALT was developed to simulate acid disposal conditions. It involves a series of leach tests with increasing volumes of H2S04 added to each test, so that the most acid leachate solution has a pH less than 2.5 after 18 hours of mixing. The results showed that, as expected, the lower the pH of the leaching solution, the more metals that were leached from the sludge. Iron, aluminium, copper and zinc began to be leached at a pH values of 3,4.5, 5.5 and 6.5 respectively. Concentrations of leached iron and aluminium increased exponentially with decreasing pH, whilst copper and zinc concentrations increased linearly. None of the reagents investigated to date provided significantly different results from the other reagents, other than Bauxsol which leached more aluminium. Calculated activities of iron in the leachate fell close to the solubility curve for ferrihydrite, but activities for copper and zinc in the leachate fell well below the solubility curves of their hydroxides, suggesting that copper and zinc are not precipitated as simple hydroxides. The results of this laboratory study show that ARD treatment sludges are inherently unstable under acid conditions and should therefore never be disposed of in a potentially acid environment (such as underground or open-cut mine, ARD collection pond, tailings dam or waste rock piles). As the chemical stability of sludges generated with different reagents does not vary greatly, choice of treatment reagent should be determined by other factors (cost, ease of use, physical properties of sludges). Keywords: acid rock drainage, leach tests, chemical stability, treatment, sludge, lime, limestone, KB1, Bauxsol. 32 Email: d.mcdonald@latrobe.edu.au
Geological Society Abstracts 75
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Envinnental Sciences Conference, La Trobe University September, 2004
STRUCTURE OF THE SUBDUCTING PACIFIC LATE BENEATH THE MARIANA ARC: EVIDENCE OF A TEAR FROM P-WAVE TOMOGRAPHY MEGHAN S. MILLERS'2. Aiexei Gorbatov^, Brian L N . K e n n e t t \ Robert J. Stern^ Zohar Gvirtzman® ^ Research School of Earth Sciences, Australian National University, Canberra, ACT 2 Australian Crustal Research Centre, School of Geosciences, Monash University, Clayton, VIC 3 FREE, JAMSTEC, Yokosuka 237-0061, Japan ^ Geosciences Departnnent, University of Texas at Dallas, Richardson, TX, USA ® Geological Survey of Israel, Jerusalem, Israel
Seismic tomography has developed into one of the most effective and significant sources of information in modern geophysical research, specifically in understanding subduction zone dynamics. The Western Pacific convergent margin is a well studied area, but as more data is collected and technology improves further detailed observations and theories are being developed. New tomographic images of the Mariana Arc region were produced by a threedimensional ray-tracing inversion algorithm adapted by Gorbatov & Kennett [2003] which have greatly improved resolution of gradients and strong variations in wave speeds. Although the images obtained from the Mariana arc show relatively low amplitudes of heterogeneity due to the lack of seismic stations in the area, details of the three dimensional geometry and morphology of the Pacific Plate subducting beneath the Philippine Sea Plate have been clearly imaged. The steep dip of the Pacific plate and the curvature of the slab beneath the Mariana arc are visualized with unprecedented detail in three dimensions. A combination of imaging P-wave tomography and seismicity have confirmed the presence of a near vertical tear in the subducting plate at the southern end of the Mariana arc that divides the arc into two distinct segments: the steeply dipping curved slab that penetrates the lower mantle and a short (200 km depth) slab beneath the Challenger Deep segment of the arc.
Keywords: slab tear, tomography, subducting lithosphere, Mariana Arc, Challenger Deep, three dimensional model Emaihmeghan.miller@anu.edu.au
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Envimental Sciences Conference, La Trobe University September, 2004
LITHOLOGICAL MAPPPING AND GEOTECHNICAL SURVEY OF KINTORE OPEN PIT BROKEN HILL, NSW STEPHEN MORAN University Of Melbourne
The Neoproterozoic Broken Hill Block in the Willyama Supergroup contains the giant (280 Mt) Pb-Zn-Ag Broken Hill Orebody. The orebody is hosted in a package of metasedimentary and meta-igneous rocks known as the Broken Hill Group. The region has undergone granulite fades metamorphism, intense deformation and subsequent widespread retrogression in a complex geological history. Lithological and structural mapping of the Kintore Open Pit on the CBH Resources Ltd mine lease, CML7 and a review of previous geological data have allowed analysis of deformation and metamorphic history around the ore body and relationships between the ore bodies and their host rocks. Four ductile deformation and up to three brittle deformation events are recognised on CML7 and have deformed and remobilised the ore bodies. D1 is associated with high-grade (granulite fades) metamorphism forming a bedding parallel S1 foliation, recumbent folding and high-grade shearing; the entire sequence mapped in Kintore Open Pit is an overturned limb of an F1 fold nappe. A second high-grade (granulite fades) event formed upright folds, high-grade shear zones and crenulation of the S1 cleavage; Kintore Open Pit is located on the western limb of the Broken Hill Anticline that hosts the main Broken Hill orebodies. D3 and D4 ductile deformation are low-grade (greenschist fades) events that have caused retrogression of S1 and S2, the deformation has resulted in small open folds and reactivation of D1 and D2 shear zones. Brittle deformation occurred late in the geological history of the ore body probably during uplift and erosion. This paper discusses the geochronology and deformation of the Broken Hill orebody and the geotechnical implications for mine planning.
Keywords: Broken Hill, mine leases, lithological mapping, geotechnical, deformation, geochronologv. Email: s.moran1@ugrad.unimelb.edu.au ^^
Geological Society Abstracts 75
of Australia
Victorian
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Earth
& Envimental Sciences Conference, La Trobe University September, 2004
THE EVOLUTION OF GROUNDWATER IN THE TYRRELL REGION, SOUTH-CENTRAL MURRAY BASIN, VICTORIA, AUSTRALIA B. PETRIDES^, I. Cartwright\ & T.R. Weaver 1 Hydrogeology and Environnnental Research Group, School of Geosciences, Monash University, Clayton, Victoria 3800, Australia. 2 Hydrogeology and Environmental Research Group, Department of Earth Sciences, Melbourne University, Parkville, Victoria 3010, Australia.
The Tyrrell hydrogeological system consists of two major aquifers: 1) the confined Renmark Group aquifer; and 2) the overlying unconfined Parilla Sands aquifer. Groundwater recharge occurs at the southern margin of the Murray Basin and flows in a north/north-westerly direction towards Lake Tyrrell, the major discharge salt lake in the area. Typical hydraulic gradients in both aquifers are approximately 0.0025 m/m. Horizontal hydraulic conductivity is -0.5 to 5 m/day in the Parilla Sands and to 7 m/day in the Renmark Group. The groundwater chemistry of regional groundwater shows little spatial variation. At individual sites the groundwater from the Parilla Sands is generally more saline than that from the underlying Renmark Group; however, the chemistry is generally similar. These data imply that vertical groundwater flow in this area is important. Groundwater from both aquifers is Na-CI type, with Na comprising more than 80% of the cations and CI attributing more than 85% of the anions. Stable isotopes and Br/CI ratios indicate that groundwater is entirely of meteoric origin and has undergone evaporative enrichment with only minor halite dissolution. The low saturation indices for gypsum imply that gypsum dissolution does not control Ca concentrations, although gypsum dissolution is the most likely source of sulphate. A lack of correlation between Ca and Mg and Dissolved Inorganic Carbon (DIC) indicate that carbonate dissolution is not the major process controlling Ca and Mg contents in this region. The loss of calcium is mainly attributed to Ca sorbing onto kaolinite at low TDS, and the formation of Cabeidellite clays. Ion-exchange reactions with clays that remove Na from groundwater and add divalent cations such as Mg is also evident. The degree of water-rock interaction in this region is low as saturation with amorphous silica is yet to be reached. This also implies that processes associated with primary salinity and the mineralogy of the clays has a more dominant control on groundwater chemistry in this region of the Murray Basin.
Keywords: Chemistry, Groundwater, Lake Tyrrell Email: benp@mail.earth.monash.edu.au
Geological Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
UNUSUAL MORPHOLOGICAL FEATURES IN FOSSIL MARSUPIALS FROM THE EARLY PLEISTOCENE OF VICTORIA K. J. PIPER School of G e o s c i e n c e s , M o n a s h University, Victoria 3800, Australia
Preliminary studies of the Nelson Bay Local Fauna, Portland, Victoria, have revealed a variety of unusual features in otherwise common Late Pleistocene genera and species. Differences exist mainly in the relative sizes of the teeth, but also in some morphological characters suggesting these taxa may be slightly more primitive. This is consistent with the dating of this fauna as early Pleistocene, but may also be the result of the fauna occupying a relictual palaeohabitat. Two species of the large, extinct kangaroo Protemnodon Owen differ in the relative proportions of the lower molars and morphology of the incisors. A possible new species of the 'marsupial rhino' Zygomaturus Macleay is represented a by a single upper premolar. It is relatively small and differs in detail from the large. Late Pleistocene Zygomaturus trilobus. Specimens of the 'marsupial tapir' Palorchestes Owen are close to the Plio-Pleistocene Palorchestes parvus but are smaller in size and may also represent a new species. The majority of the taxa so far identified in the Nelson Bay Local Fauna are browsers or arboreal suggesting a forested or wooded environment dominated this section of coastal Victoria. The relatively small sizes of these otherwise large species may be explained by a combination of their slightly older age (and therefore possibly slightly more primitive stage of evolution), together with their inhabitation of a restricted palaeoenvironment, resulting in an endemic fauna. The possum-like Ektopodontidae, known predominantly from the rainforests of the OligoMiocene of central Australia, have now been recognised in three Pliocene sites along the southwest coast of Victoria. This together with their last known occurrence in the Nelson Bay Local Fauna suggests that wet sclerophyll forest persisted in this coastal region up until the early Pleistocene, and may have acted as refugia for now extinct browsing and arboreal marsupials.
Keywords: Nelson Bay, Macropodinae, Zygomaturinae, Palorchestidae, Marsupialia, Early Pleistocene. Email: kpiper@mail.earth.monash.edu
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
THE VICTORIAN MALLEE : GEOMORPHOLOGY, STRATIGRAPHY, GEOCHRONOLOGY AND ENVIRONMENTAL EVOLUTION AMY PRENDERGAST University of Melbourne, Melbourne, Australia
Climatic oscillations related to glacial and interglacial cycles throughout the Quaternary have had a profound and continuous effect on the Earth and its biota. In Australia, the lack of glacial cover and the relative tectonic stability of the low-lying, arid landscapes have enabled the preservation of a reasonably continuous record of Quaternary climatic change. This record of deep weathering profiles and relict landforms is particularly well preserved in the semi-arid Mallee region of the Murray Basin, southeastern Australia. Human occupation in this region extends beyond the Last Glacial Maximum. The shifting climatic regimes from the Late Pleistocene to the Holocene are explored in this study with particular reference to the last 40,000 years when humans are known to have inhabited the landscape. A multidisciplinary approach has been employed to study the complex environmental and cultural evolution of the Victorian Mallee. Regional geomorphic mapping, archaeological survey and stratigraphic analyses have revealed evidence of ongoing climatic oscillations. The micromorphology of Holocene mussel shells (Alathyria jacksoni) collected from an Aboriginal shell midden within the field area were studied using Scanning electron microscopy (SEM) and cathodoluminescence (CL). Aragonitic growth band sequences have been interpreted as seasonal. Isotopic analyses from these seasonal growth bands reveal an estimate of the palaeotemperatures at the time of mussel shell growth, thus, an approximation of palaeoclimate at the time of human occupation. The age of the midden and underlying landforms has been determined using optically stimulated luminescence (OSL) and radiocarbon dating. By combining multivariate geomorphic, stratigraphic, archaeological and geochronological evidence, this study provides a temporally constrained model of environmental evolution in the Victorian Mallee, contributing to a greater understanding of the climatic and cultural evolution of southeastern Australia.
Keywords: Geology, geomorphology, climate change, archaeology, Australia, oxygen isotope, optically stimulated luminescence, radiocarbon dating, Alathyria jacksoni Email: a.prendergast@ugrad.unimelb.edu.au
^'
Geological Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
SALT LAKES AND THEIR INFLUENCE ON THE SALINITY OF SURFACE WATERS IN MOUNT EMU CREEK AND FIERY/SALT CREEK, WESTERN VICTORIA M. RAIBER and J. A. Webb
As part of an extensive study linking the geology, and especially the different basalt phases, to the salinity distribution within a eSGOkm^ section of the eastern Hopkins Catchment, groundwater/ surface water interactions along Mount Emu Creek and Fiery/Salt Creek were investigated. The creeks were sampled at regular distances to locate sources of saline input. The salinity of Mount Emu Creek was measured in June after a period of high rainfall; Fairy Creek & Salt Creek were measured in May (after a period of low rainfall) and remeasured (field parameters only) in June (after high rainfall, to allow for a comparison with the results from Mount Emu Creek). The salinity measurements were then compared to the distribution of salt lakes and the geology to look for correlations. In Fiery Creek the salinity rose from low values (1.39mS/cm) close to its headwaters to very high (14.42mS/cm) just before entering Lake Bolac, probably due to the input of saline water from the salt lakes between Streatham and Lake Bolac. Salt Creek exhibited fairly constant, generally high salinities (10.7-11.54mS/cm). The repeat measurements for Fiery and Salt Creeks after high rainfall showed lower values at some sampling points due to a dilution by the rainfall, but at other points significantly higher values were recorded (e.g. rising from 4.28mS/cm in May to about 12.9mS/cm in June), due to flushing of saline water into the creek. The salinity of Mount Emu Creek increased steadily downstream from relatively low values (3.1mS/cm) north of Langi Kal Kal to 5.72mS/cm at Skipton, probably as a consequence of groundwater inflow from salt lakes. The salinity increased further to 8.38mS/cm between Pura Pura and Darlington (which is also the area with the highest occurrence of salt lakes within the field area), indicating that there is a considerable inflow of saline water from the adjacent salt lakes. Downstream of Darlington, the salinity constantly decreased; there is no mapped salinity in lakes and drainage lines in this part of the study area, probably due to the higher rainfall, and therefore little saline water input into the southern part of Mount Emu Creek. Thus the salt lakes are a major source of saline water into the creeks. The reason that salt lakes occur in specific sections of the field area is difficult to determine, but is probably related to the topography and geology. Many salt lakes occur in topographic lows, and also occur where the bedrock underlying the basalt is at or very close to the surface. The relatively saline groundwater within the bedrock comes to the surface at the lakes and undergoes extensive evaporation, causing salt accumulation within the lakes over time.
Keywords: Groundwater/surface water interactions, basalt, salinity. Email: mraiber@students.latrobe.edu.au
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
SPATIAL VARIATION IN STRUCTURAL STYLE DURING MINERALISATION WITHIN THE BASALT CONTACT ORE ZONE, MAGDALA GOLD MINE, WESTERN VICTORIA. J. A. ROBINSON, C.J.L. Wilson and T.J. Rawling School of Earth Sciences, T h e University of Melbourne, Victoria 3010, Australia
The distribution of gold within the contact ore zone adjacent to the Magdala Basalt is controlled by quartz-carbonate-chlorite extension veins and shear zones hosted within sulphidic mudstone. The distribution of auriferous veins is however highly variable and they rarely co-exist spatially with shear-hosted mineralisation. Mineralised extension veins concentrate within stilpnomelane and/or silica alteration zones, particularly where the underlying contact is steep (>65o). Mineralisation occurs as a halo adjacent to the veins, exclusively within the altered mudstone and is most extensive immediately overlying the basalt contact. While the mineralised veins tend to be relatively flat lying their orientation is variable, as are cross cutting relationships between veins. Timing relationships indicate that the formation of the mineralised veins postdates mineralisation within the overlying Central Lode System. Previous interpretations regarding the origin of the mineralised veins have tied their formation to either fracture-mesh infilling early in the seismic cycle (pre-Central Lode) or to sinistral oblique movement on west dipping faults post-Central Lode. However, results of this study indicate the veins formed as a consequence of fluid overpressure around the basalt contact, post-Central Lode and late during, or post the sinistral oblique transport. Fluid overpressure along the contact results from a combination of permeability reduction due to localised hydrothermal alteration and the alignment of pre-existing faults in orientations not favorable for reactivation relative to the changing stress field. Mohr diagram analyses of the structures in the contact ore zone demonstrate that with subtle changes in the orientation of faults (5 to 10°) and the addition of alteration, vein hosted mineralisation may occur on some fault segments, while at the same time shear hosted mineralisation occurs on others.
K e y w o r d s : M a g d a l a Gold Deposit, Fluid overpressure, Extension veins Email: j.robinson@pgrad.unimelb.edu.au
Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
LITHOLOGICAL MAPPING IN A VEGETATED ENVIRONMENT USING ASTER & GEOPHYSICAL DATA L.T. ROBSON, M J . Roach and R.R Berry Departnaent of Earth Science, University of Tasmania, Private Bag 79, Hobart, TAS 7001.
ASTER satellite imagery and airborne geophysical data were used to attempt to map lithologies in the Central Midlands of Tasmania, Australia. The study area was selected as a test site as it is comprised of a diverse range of lithologies, vegetation and landuse. The geology consists of flat lying Permian - Triassic sedimentary rocks extensively intruded by thick sheets of Jurassic Dolerite and overlain by thin sequences of Cainozoic sediments and basalt. Two level 1B ASTER images were merged to cover the project area. The airborne geophysical data, acquired in 1999 for Geoscience Australia, was originally grided to 40 m cell size and subsequently resampled to 15 m cells to match the ASTER data. Gamma ray, Delphi (VNIR) and PIMA(SWIR) spectra were acquired from 126 sample sites, to generate statistical comparisons between lithologies. Delphi and PIMA spectra were resampled to simulate ASTER VNIR and SWIR bands. Statistical analysis of the resampled spectra indicated that nine of the original 21 geological units, identified from 1:250,000 scale mapping, should have been discriminated by ASTER and radiometrics data. The best false colour image for lithological discrimination was found to be an RGB:741 combination, although a band ratio image (RGB:1/4,2/3,3/9) was also effective for discriminating between dolerite and basalt, and sandstones and mudstones. Analysis of radiometric data showed that quartz-rich and fluviatile sandstones units could be differentiated, and that colluvium, alluvium and regolith could be discriminated from fresh mudstone and siltstone units. TMI data was useful for defining geological boundaries, however, was not useful for classifying surface lithology. The accuracy of the final classified geology images was significantly affected by the variable nature of topography, landuse, and vegetation. Lithological classification based on either ASTER or radiometric data alone resulted in overall accuracies of only 35.5% and 35.3% respectively. Classification of the combined ASTER and radiometric dataset achieved an overall accuracy of 46.1%
Keywords: ASTER, geophysics, spectra, classification, geology, vegetation.
Email: ltrobson@utas.edu.au
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
ESTIMATING THE LONGEVITY OF LIMESTONE DRAINS FOR THE TREATMENT OF ACID MINE DRAINAGE S. SANTOMARTINO and J.A. Webb Departnrient of Earth Sciences, La Trobe University, Bundoora, Victoria 3086
Limestone-based systems are often implemented in the treatment of acid mine drainage (AMD), but their lifetime has often been less than anticipated. When AMD contains high levels of Fe2+, the precipitation of Fe hydroxide on the limestone surface is the variable that determines the longevity of the limestone system. This study used a small-scale laboratory experiment to determine the thickness of the Fe coating encapsulating the limestone particles when the system lost its maximum neutralising potential. Synthetic AMD containing 100 mg/L Fe and a pH of 4-4.8 was pumped at a rate of 2.75 mL/ min up a column containing 78.46g of limestone particles with a total surface area of 555.28 cm2. The experiment ran for 1110 hrs until effluent pH dropped from a maximum of 6.45 to 4.9. After 744 hrs, a marked increase in the rate of pH decline occurred, when the system began to fail. This was due to the formation of Fe hydroxide coatings on the limestone grains. The coatings were composed of lepidocrocite/goethite in three distinct layers: an initial thick porous orange layer, overlain by a dense dark brown crust, succeeded by a layer of loosely-bound, porous orange globules. When the dense crust completely encapsulated the limestone grains, it formed a diffusion barrier that slowed down limestone dissolution and caused the marked decline in neutralisation rate and the effective failure of the system. The median thickness of the Fe coating surrounding each limestone particle at this time (initial porous layer and dense crust layer inclusive) was 80 (m as measured on SEM images. Between the coating and the limestone substrate was a 60 (m wide void, so that agitation of the limestone sample would readily remove the coating from the limestone surface. In the experimental system, the time for sufficient Fe hydroxide to precipitate on the limestone to cause a distinct decline in the rate of neutralisation was defined by: t (yrs) =
surface area fm^)
X
4.4
fraction Fe retained in system X [Fe^^] (mg/L) X flowrate (L/hr)
At this time the limestone in the drain would need to be replaced or mechanically agitated to remove the Fe hydroxide coating, to allow the system to continue functioning at its maximum potential.
Keywords: Anoxic limestone drains, open limestone drains, lepidocrocite, goethite, Fe encapsulation Email: s.santomartino@latrobe.edu.au ^•
Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
THE FAUNA OF THE BUCHAN CAVES, SOUTH EAST VICTORIA. D.A. SHEAN School of Geosciences, Monash University, Clayton, Victoria, Australia
The Buchan Caves have preserved an unusual and interesting glimpse into the Pleistocene of South Eastern Victoria. Of particular note is the abundance of mandibular and postcranial material of the rare species Palorchestes azael and Palorchestes parvus. The absence of other large quadrapedal marsupials, such as Diprotodon optatum and Zygomaturus trilobus, which in many cases, but not all, are found in faunal assemblages that include P azael, is unusual and warrants further research. Found earlier this year, is an unusual pelvic element that may prove to belong to the rare hysiprimnodontid Propleopus oscillans and provide the first evidence of propleopids in South Eastern Victoria A mandible of an unknown peremeleid may represent a new species of bandicoot that inhabited the Buchan region during the Pleistocene. This investigation also revises the ideas regarding dietary habits of Palorchestes, due to research on the structure of the forelimbs of this animal and re-evaluation the environmental conditions prevalent at Buchan during the Late Pleistocene. From the absence of Diprotodon and Zygomaturus, two conclusions have been drawn. The first suggests that the environmental conditions at Buchan were unfavourable to large marsupials, effectively isolating the Palorchestes species within this region. The second hypothesis is that this area may reflect that there was some sequencing of Pleistocene extinctions.
Keywords: Buchan Caves, Palorchestes azael, Propleopus oscillans. Email:dino_girl28@hotmail.com
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
Nd ISOTOPIC CONSTRAINTS ON THE GENESIS OF THE RIWAKA Ni-Cu DEPOSIT, SOUTH ISLAND, NEW ZEALAND R.G.SMITS, S.W.Beresford, & B.F. Schaefer
School of Geosclences, Monash University, Clayton, Victoria 3800, Australia.
The 330Ma (40Ar-39Ar of hornblende separate) Riwaka Complex is a northeast to southwest trending macrodyke approximately 40km long, and up to 3km wide with sub-vertically layered mafic to ultramafic units. The lithologies that make up the Riwaka Complex range from wehrlites to hornblende-rich gabbros, along with geochemically similar, though spatially ambiguous diorites. The western side of the complex consists of ultramafic cumulate units and the eastern side is predominantly gabbroic. The eastern side of the complex hosts disseminated to matrix NiS mineralisation that is parallel to the layering and contact of the intrusion. The diorites appear to crosscut the mafic and ultramafic units of the Riwaka Complex. Mineralisation in orthomagmatic deposits such as the Riwaka Complex is widely considered to be related to the interaction of a primitive magma with an external sulfur source. The contamination of the primitive magma by the sulfur-hosting unit leads to S-saturation and the precipitation of sulphides. We have undertaken a detailed transect across the Riwaka Intrusive Complex. Sm-Nd isotopic and trace element geochemistry data has been obtained from the Riwaka Complex, so as to better constrain the parental magma, geochemical architecture and the processes that have led to nickel sulphide genesis. Initial Nd isotopic compositions (144Nd/143Nd) of the Riwaka Complex are between 0.512059 and 0.512737 and indicate both radiogenic and relatively primitive composition. No systematic correlation exists between the mineralisation and contamination. The origin of the Riwaka Complex in a vertically layered macrodyke remains enigmatic and is the focus of ongoing research.
Keywords: Riwaka Complex, radiogenic isotopes, nickel, geochronology Email: Russell.Smits@sci.monash.edu.au
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Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
PALAEOENVIRONMENTAL INTERPRETATION OF THE WHALERS BLUFF FORMATION, PORTLAND, SOUTH-WEST VICTORIA THROUGH THE ANALYSIS OF EXTANT OSTRACODA AND BENTHIC FORAMINIFERA. BRENT SOUTAR School of Ecology and Environment, Deakin University, 221 Burwood Highway, Burwood, Victoria, Australia 3125.
The Whalers Bluff Formation located along the Portland cliffs, Victoria, contains outcrops of clays, oyster beds and sandy limestones deposited during the middle Pliocene. The formation is capped by basalt and underlain by Miocene limestone. The specific stratigraphical section of the Whalers Bluff Formation considered in this study was that previously described as the "meatworks section" by Boutakoff. In this study this section has been subdivided into eight distinct beds. The lower three beds are primarily of fossiliferous muds and the upper 5 beds are fossiliferous sandy limestones. All beds contain abundant foraminifera with ostracods being common in around half the beds. Preliminary results show the formation to be mainly lagoonal (and perhaps partly estuarine) in origin based on the large presence of the extant foraminifera Ammonia beccarii and various characteristically lagoonal / estuarine ostracod species. Preliminary results also suggest that warmer waters off south-western Victoria prevailed during the middle Pliocene compared to the present day. This is based on the rare occurrence of the ostracod species Paranesidea fortificata (s.l.) in the Whalers Bluff Formation; a species that has not been recorded in present day waters of Bass Straight but which occurs in relatively warmer shallow seas and embayments further north along the east Australian coastline.
44 Email: baso@deakin.edu.au
Geological Society Abstracts 75
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Envimental Sciences Conference, La Trobe University September, 2004
KARST DEVELOPMENT AT NARACOORTE, SOUTH AUSTRALIA: WHEN? WHY? & HOW? SUSAN WHITE & John Webb Earth Sciences, Latrobe University Bundoora, Victoria
The Lower Southeast of South Australia and a substantial part of southwestern Victoria is a limestone karst province, which comprises extensive areas where cave and karst development is limited interspersed with areas of atypical intensive karst development, such as at Naracoorte. At Naracoorte dollnes, uvalas and blind valleys characterise the surface karst. The caves range from simple single passages to complex mazes, and passages trend predominantly northwest/southeast. Cave walls retain evidence of solutional features. The caves contain a range of fossiliferous clastic sediments and dated speleothems. The fossils accumulated through pitfall entrances in several episodes during the Middle Pleistocene (100,000-400,000 years ago). The development of the Naracoorte karst is constrained by the age of the enclosing Gambier Limestone (Oligo-Miocene), and probably post-dates the maximum sea-level transgression at - 7 Ma. The following Pliocene-Pleistocene regression deposited a series of subparallel beach dune ridges, progressively younging seaward. Cave formation probably occurred in a relatively narrow window of time between uplift along the Kanawinka Fault in the late Pliocene, and draining of the caves by the sea level fall at -800-900 ka, during deposition of the West Naracoorte Range. The main period of cave development probably began during deposition of the East Naracoorte Range at Ma, as prior to this the cave area was flooded by the sea, and no cave formation could occur. The caves may have initially formed along the freshwater/seawater interface extending inland from the East Naracoorte Range, and were subsequently enlarged by groundwater flow as sealevel fell between 1.1 Ma and 800ka. Because the water table was not stable for a substantial period of time, there was no preferential development of passages at a particular elevation. The incision of Mosquito Creek postdates uplift along the fault and occurred during the 1.1 Ma to BOOka sealevel fall. As the water table dropped due to sea level fall and creek incision, the caves partially, then completely drained. Most of the collapse that characterises many of the Naracoorte caves probably occurred progressively as the water drained from the passages; at least some collapse entrances could have formed at this time. Solution pipe entrances have formed since the main cave development, intersecting the older main cave passages and enabling sediment accumulation. Cyclical wet and dry conditions occurred over the last 500ka as landscape modification occurred throughout the Pleistocene to the present.
Keywords: Naracoorte, Cainozoic, Pleistocene, karst, speleogenesis, landscape evolution Email S.White@latrobe.edu.au
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AUTHOR INDEX Author
Page
Author
V. BARRAS A.N. BEAR D.A BENNhl IS S.W. Beresford R.F. Berry M.E. BORMANN K. BROMFIELD M.N. BURDEI 1 A.L. BUSH
13 14 15 43 40 16 17 18 19
D.W Maidment H. Malano M. McCaskill D.M. MCDONALD M.S. MILLER s. MORAN R. Musgrave
18 27 15 32 33 34 23
B. PETRIDES K.J. PIPER A. PRENDERGAST
35 36 37
E.A. CARRARA 1. Cartwright R.A.F. Gas J.F. Costelloe
20 20, 35 14 28
M.RAIBER T.J. Rawling M.J. Roach J.A. ROBINSON L.T. ROBSON
38 39 40 39 40
A. Dugdale
23
M.D. EDWARDS A. ELMAHDI M.R ERNEST D. Etheridge
21 27 22 13
A. Gorbatov J.M. GREWAR S. GROVER Z. Gvirtzman
33 23 24 33
S. SANTOMARTINO B.F Schaefer D.A. SHEAN 1. Simmonds R.G. SMITS B. SOUTAR R.J. Squire R.J. Stern
41 43 42 13 43 44 23, 26 33
T.R. Weaver J.A, Webb
G.R. HAMSON M Hand D.A. HENRY A.L. Herczeg
25 18 26 28
A.W. Western S. WHITE C.J.L.Wilson
12, 20, 35 15,21,22, 32, 38,41, 45 28 45 21,24, 37
E.C. IRVINE
28
R. Zollinger
15
B.L.N.Kennett S. Khan B.M. KINNA
33 27 29
T.D. LAWTON L.D. LEADER
30 31
T.K. AL-HOSNI
12
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