Issuu

The Geological Society of Australia

ABSTRACTS Number 111

2014 SELWYN SYMPOSIUM & MEMORIAL LECTURE I The Nullarbor Plain: Recent Advances Friday October 3^^2014 Elizabeth Murdoch Theatre The University of Melbourne

The Geological Society of Australia ABSTRACTS

Number 111

The Geological Society of Australia Inc. Victoria Division www.gsavic.org

SELWYN SYMPOSIUM 2014 The Nullarbor Plain: Recent Advances.

Friday 3 October 2014 Elizabeth Murdoch Theatre, University of Melbourne

Editor: Susan White Environmental Geoscience La Trobe University 3068

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

Geological Society of Australia Inc. Victoria Division ISSN 0729 011X Abstract No 111 Editor: Susan White

Preferred Citation: White, S. (ed) 2014 The Nullarbor Plain: Recent Advances. Selwyn Symposium 2014, University of Melbourne, October 2014. © Geological Society of Australia Abstracts 111,27 pp. Example Citation for abstracts in this volume: Webb, J., 2014 The Nullarbor Plain - Flat but far from Boring. In: White, S. (ed) 2014 The Nullarbor Plain: Recent Advances. Selwyn Symposium 2014, University of Melbourne, October 2014. © Geological Society of Australia Abstracts 111, pp 11-12.

Copies of this publication may be obtained from: Geological Society of Australia Suite 61 104 Bathurst St Sydney, NSW 2000 Email:info@gsa.org.au

Acknowledgements: The organising group and the GSA Division committee would like to thank the organisers of KR7 for their support.

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts XX

The Nullarbor Plain: Recent Advances 2014 TABLE OF CONTENTS Organisation of Selwyn Symposium 2012

Alfred Richard Cecil Selwyn Biography

Foreward

Detailed Program

The Selwyn Medal

2014 Selwyn medallist: Dr Ian Duddy

2014 Selwyn Memorial Lecture

Professor Paul Williams Downstream Reflections of an Upstream Environment Plenary Lecture: John Webb

(La Trobe University

The Nullorbor -flat but for from boring. Jon Clarke

(Canberra)

Advances in Understanding the evolution of the Eucia Basin over the past decade. Jon Woodhead

(University of Melbourne)

Nullarbor speleogenesis: constraints from U-Pb geochronology of the Nullarbor Plain John Hellstrom (University of Melbourne) Late Quaternary speleothem geochronology of the Nullarbor Plain.

Russell Drysdale

(University of Melbourne)

Stable oxygen and carbon isotope records from Nullarbor speleothems. Kale Sniderman (University of Melbourne) Late Neogene vegetation and climate history of the Nullarbor Plain: new insights from fossil pollen records of U-Pb-dated speleothems.

Elen Shute (Flinders University) Million-year menagerie: the Thylacoleo Caves fossil fauna.

Shannon Burnett (La Trobe University) Shallow caves and blowholes on the Nullarbor Plain, Australia — Flank margin caves on a low gradient limestone platform. Liz Rogers & Ian Lewis (Cave Diving Association Australia, La Trobe University)

Underwater geology and geomorphology of the southern Nullarbor Ian Lewis (Latrobe University) The role of tectonics on the deep caves array - a template for large global Tertiary karst areas.

Susan White & Gresley Wakelin-King (La Trobe University, Wakelin Associates) Natural heritage values of the Nullarbor and National Heritage List criteria.

Geological Society of Australia Abstracts XX

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

The Selwyn Symposium for 2014 has been organised by the Victorian Division Committee in conjunction with the organising group of KR7. The Geological Society of Australia, Victoria Division The Geological Society of Australia (GSA) was established in 1952 as a learned nonprofit organisation. The Society's objectives have been expanded to promote, advance and support the Earth Sciences within the scientific and wider communities. The GSA Victoria Division holds scientific meetings on the last Thursday of each month at the University of Melbourne starting at 6.15 preceded by light refreshments from 5.30pm. It publishes geological books (such as the Geology of Victoria), and acknowledges geological leadership and accomplishment through various awards through the Selwyn Award and Symposia. Anyone interested is also welcome to attend the monthly committee meetings of the GSAV, which usually begin at 4 pm in a venue near the general meeting venue. For further information check our website: www.gsavic.org.

GSAV Committee 2014 OFFICE BEARERS Chair: Vice-chair: Secretary: Treasurer:

David Cantrill Vacant Adele Seymon Barbara Wagstaff

SUBCOMMITTEES Awards: Bicentennial Gold: Education: Heritage: Membership: Newsletter:

Ingrid Campbell Gerhard Krummel Shannon Burnett Susan White Vacant Kieren Isles

Program: Publications: Promotions Webmaster: Geology of Victoria:

Vacant Vacant Vacant Stefan Vollgger Bill Birch

COMMITTEE David Moore Susan White Kieren Isles Shannon Burnett Estephany Marillo Hamed Aghaei Karen Kapteinis

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts XX

The Geological Society of Australia Victoria Division presents the SELWYN SYMPOSIUM

2014

Friday 3 October 2014 www.gsavic.org

Elizabeth Murdoch Theatre University of Melbourne

Alfred Richard Cecil Selwyn (1824-1902) The Selwyn Memorial Lecture was introduced in 1984 to commemorate the work of A.R.C. Selwyn, the first Government Geologist of Victoria. This year represents the 155^^ anniversary of the Government Geological Survey in Victoria. In recent years the Lecture has followed a symposium, involving invited speakers on a significant theme for Australian Geology, to celebrate Selwyn's work. Alfred Selwyn was born in Somerset, England in 1824, and had a strong Church of England upbringing. He was educated in Switzerland where he developed an enthusiasm for geology. At the age of 21 he joined the Geological Survey of Great Britain under the direction of A. C. Ramsay in North Wales and was soon entrusted with independent mapping of large areas with key Silurian rocks. The discovery of Gold in Victoria in 1851 led Governor La Trobe to ask the Colonial Office in London for "a gentleman possessed of the requisite qualifications and acquaintance with geological science and phenomenon." Selwyn was awarded the post at an annual salary of 500 pounds and arrived in early December 1852. Almost immediately he commenced a series of wide ranging reconnaissance trips during which he studied the geology of Victoria with excursions into Tasmania and South Australia. Among many of the early records, the Geological Survey holds an original watercolour version of his 1856 map of the Yarra Basin and Western Port. i I

Selwyn set up the Geological Survey proper in 1856 and gathered around him and trained a team of geologists including: Alpin, Ulrich, Wilkinson, Daintree, Taylor, Brown and Etheridge. They subsequently occupied senior positions in all mainland State Geological Surveys and became renowned in the early annals of Australian geology. Selwyn and his team established the 6-mile x 9-mile Victorian quarter sheet mapping programme of which 65 were produced. Selwyn was quiet and reserved man of indomitable disposition who carried out his plans despite all hindrances and achieved an amount of work that few could emulate. However, conflict arose from the overlapping activities of mining surveyors. The Survey often held views on scientific standards and policies opposed to those of the colonial officials and legislators, in particular that of R. Brough Smyth, Secretary of Mines. Consequently, Selwyn resigned in 1869 and the Survey was disbanded for a year. Selwyn left Australia and was appointed the Director of the Geological Survey of Canada on retirement of Sir William Logan. He worked with distinction from 1869 until his retirement in 1894. Selwyn was awarded the prestigious Murchison Medal of the Geological Society of London in 1876. Other honours followed in Great Britain. The only recognition from Australia was his Clark Gold Medal from the Royal Society of New South Wales in 1884. He is commemorated in Victoria by an annual Geological Society of Australia Victoria Division lecture, symposium and medal.

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts XX

FOREWORD Just over 45 years ago, John Dunkley and Tom Wigley edited for the Sydney University Speleological Society (SUSS) and the Cave Exploration Group (South Australia) (CEGSA), the first review of the speleological work of the Nullarbor Plain, The Caves of the Nullarbor. Although work has continued for the past 47 years, no replacement has ever been produced. Karst science has changed and progressed immensely in the past years and particularly on the last 15 years. Especially the improvements in dating, the discovery of the megafauna Thylacoleo' caves in 2002, and the use of ultra light aircraft for documenting new caves. The 2014 Selwyn Symposium is capitalising on the presence of many international visitors attending the KR7 earlier in the week. Although publications have been produced and presentations have occurred at various karst conferences, especially the Australian Speleological Federation biennial conferences, we have not had a specialist symposium specifically on the Nullarbor in recent times. This is a great opportunity to show what Australian karst workers have been doing on the plain. Enjoy!

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts XX

DETAILED PROGRAM 8.00 - 9.00 9.05 9.15 -10.00 10.00 -10.30 10.30 -11.00 Session 2 11.00 -11.30 11.30 -12.00 12.00 -12.30 12.30 - 13.30 Session 3 13.30 -14.00 14.00 -14.30 14.30 -15.00 15.00 - 15.30 15.30 -16.00 Session 4 16.00 -16.30 16.30 -17.00 17.00 -17.10 17.10-18.00 18.00 -18.15 18.15 -19.15

20.00

SYMPOSIUM REGISTRATION INTRODUCTION AND OPENING ADDRESS (Chair: Susan White) PLENARY ADDRESS A/Prof John Webb, La Trobe University The Nullarbor - flat but far from boring. Dr Jon Clarke, Canberra Advances in Understanding the evolution of the Eucia Basin over the past decade. MORNING TEA Chair: John Webb Prof Jon Woodhead, University of Melbourne Nullarbor speleogenesis: constraints from U-Pb geochronology. Dr John Hellstrom, University of Melbourne Late Quaternary speleothem geochronology of the Nullarbor Plain. A/Prof Russell Drysdale, University of Melbourne Stable oxygen and carbon isotope records from Nullarbor speleothems. LUNCH Chair: David Moore Dr Kale Sniderman, University of Melbourne Late Neogene vegetation and climate history of the Nullarbor Plain: new insights from fossil pollen records of U-Pb-dated speleothems. Ms Elen Shute, Flinders University Million-year menagerie: the Thylacoleo Caves fossil fauna. Mr Shannon Burnett, La Trobe University Shallow caves and blowholes on the Nullarbor Plain, Australia — Flank margin caves on a low gradient limestone platform. Mr Ian Lewis, Latrobe University The role of tectonics on the deep caves array - a template for large global Tertiary karst areas. AFTERNOON TEA Chair: Susan White Ms Liz Rogers & Mr Ian Lewis, Cave Diving Association Australia, La Trobe University, Underwater geology and geomorphology of the southern Nullarbor. Dr Susan White & Dr Gresley Wakelin-King, La Trobe University, Wakelin Associates Natural heritage values of the Nullarbor and National Heritage List criteria. DISCUSSION & CONCLUSION DRINKS & REFRESHMENTS SELWYN MEDAL PRESENTATION to Dr Ian Duddy, Geotrack International SELWYN LECTURE Prof Paul Williams, Auckland University Downstream Reflections of an Upstream Environment SELWYN DINNER: Cafe Italia, 56 University St, Carlton (bookings required)

Selwyn Symposium 2014 University of Melboume, October 3, 2014

The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts XX

THE SELWYN MEDAL The Selwyn Medal is named in honour of Sir Alfred Selwyn, an eminent Victorian pioneering geologist and founder of the Geological Survey of Victoria. It is awarded, usually yearly, to recognise significant on-going or former contributions of high calibre to any field of Victorian geology. A candidate for this medal should have made a major contribution to new knowledge of the geology of Victoria, or a significant reinterpretation of it based on critical observations, or has contributed importantly to a major mineral or oil discovery, or have produced important geological publications or have been involved successfully in the development of the geological profession.

THE 2014 SELWYN MEDALLIST Ian Duddy has made important contributions to the Earth Sciences community in Victoria, the geology of Victoria, and many other parts of the world while based in Victoria. He has played a key role in establishing the locallydeveloped technology of apatite fission track analysis (AFTA) as a leading contributor to the field of thermochronology and to the international Petroleum Industry. lan's PhD research at The University of Melbourne involved geochemistry and the diagenetic evolution of the Early Cretaceous Otway Group volcanogenic sediments. He developed the systematic application of AFTA in a sedimentary basin setting and the discovery that fission track annealing closely parallels hydrocarbon generation in sedimentary basins. During his time at the Melbourne fission track laboratory, he helped establish AFTA as a rigorous tool for thermal history assessment as applied to hydrocarbon exploration. His fundamental fission track research and development work allowed for the prediction of fission-track parameters in geological settings, and the thermal effects of fluid flow in sedimentary basins, based on the use of fission track analysis and vitrinite reflectance data. This work led to Melbourne being acknowledged as a leading world centre in the field of Thermochronology. In 1987 Ian was one of the co-founders of Geotrack International Pty. Ltd., an international consulting company based in Melbourne, specializing in the application of AFTA to hydrocarbon exploration problems in a range of sedimentary basins worldwide. The company is export focused and leads the world in this particular field. Recognition of its expertise is clearly demonstrated in that all of the world's major hydrocarbon exploration companies are listed amongst their clients. Ian has played a central role in the company since the earliest origins within the Melbourne Fission Track Research Group and has written many hundreds of reports for clients from around the world. He continues as a director and manager in the company today. Ian has also contributed more broadly to advancing our understanding of the geology of Victoria and southern Australia, for example through his writing of Chapter 9 on the 'Mesozoic' in the most recent 'Geology of Victoria' volume in 2003. Ian Duddy has maintained his close association with the Otway Basin and has played a leading role in its use in education and demonstration of fundamental basin concepts. He enjoys showing other geoscientists, and especially students, the important lessons that can be learned in this important basin and has led numerous field excursions around the basin over many years.

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

Geological Society of Australia Abstracts XX The Nullarbor Plain: Recent Advances

THE 2014 GSAV SELWYN MEMORIAL LECTURE Paul Williams School of Environment, University of Auckland

Paul's formal qualifications include degrees from Durham, Dublin and Cambridge Universities. Before joining the staff at Auckland, he was a member of staff at the Australian National University and the University of Dublin (TCD). He has retired from teaching, but maintains an active research program. In 2007 he was the Hochstetter Lecturer (an annual award of the Geological Society of NZ), a Senior Fellow, International Association of Geomorphologists and a Hon. Life Member, National Speleological Society (USA). Paul's interests range from geomorphology through hydrology to environmental change. He has a specialist research interests in caves and limestone (karst) terrains and has completed a global review of karst World Heritage sites for the International Union for the Conservation of Nature (lUCN). He is a member of the World Commission for Protected Areas. He is a co-author (with Derek Ford) of the comprehensive book Karst Hydrogeology and Geomorphology. His current research focus is on Quaternary palaeo-climate of New Zealand. Information on this is obtained from speleothems, which contain high resolution, quantitative records of past temperatures and precipitation (from stable isotopes and trace element ratios). The records produced from this source are verified against palaeo-climate time series derived independently from tree-rings and lake sediments (by Dr Paul Augustinus and others).

Geological Society of Australia Abstracts XX

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

DOWNSTREAM REFLECTIONS OF AN UPSTREAM ENVIRONMENT P. W. Williams 1 ^School of Environment, University of Auckland, New Zealand Understanding the development of karst and caves of the Nullarbor Plain has been -and remains- a challenge. The limestones are relatively young and chalky compared to the dense crystalline limestones in which most karsts are developed; and the climate is so dry that evapotranspiration considerably exceeds precipitation. Consequently, circumstances are not auspicious for karst development. In 1963 Jennings called it "an immature, retarded karst." Yet in spite of that there are over 100 known large caves, over 150 collapse dolines and perhaps 4500 small caves and blowholes. But given the huge area - 200,000 km^ - that still not a high density, and most known caves are relatively close to the coast. Establishing a quantitative chronology of events has proved difficult. The Nullarbor limestones emerged about 35 Ma, resubmerged, and then emerged finally in the Mid Miocene about 14 million years ago. As the sea regressed, rivers sourced on the adjacent basement rocks extended across the emerging sea floor for up to 130 km, but incised only about 10 m. This could have been in the Mid Pliocene according to sedimentary evidence provided by Clarke, Alley and others. Since its emergence, dissolution has lowered the surface 30-70 m and has initiated development of the karst groundwater system. During the Late Cenozoic, when major caves were developing, baselevel would have been relatively high with the sea perhaps 50 to 30 m higher than at present. Some major advances in our understanding of the timing of events has occurred recently. This has been driven by U-Pb dating of speleothems by Jon Woodhead's group at the University of Melbourne. We now know there was speleothem deposition in Nullarbor caves in the Mid Pliocene 3.77 4.09 million years ago. The circumstances that would permit speleothem deposition in such an arid environment remain conjectural. Presumably there were rain-bearing cold front incursions from the Southern Ocean. Here evidence from the neighbouring Naracoorte karst in

South Australia helps, because the processes that drove speleothem deposition at Naracoorte would also have been felt on the Nullarbor. Research by Ayliffe, Moriarty and others at Naracoorte has shown that there were 4 or 5 wet periods with speleothem deposition in the last 500,000 years and that they coincided with stadials and cool interstadials. The pattern and dating of stadials and interstadials is particularly well-established in New Zealand (at the same latitude as Naracoorte). This information helps refine still further the global circulation circumstances that favoured speleothem deposition in southern Australia: it suggests that speleothem growth is favoured in southern Australia as interstadials cool and give way to stadials. At such times the westerly wind circulation intensifies and expands equatorwards (introducing more rain from cold fronts), lowers temperatures, reduces evapotrans-piration and leaves water surplus for percolation. Intensification of westerly wind circulation is associated with increased hemispheric temperature gradients as the polar regions cool. It has been suggested recently that an inter-hemispheric hydrological seesaw involving latitudinal migration of the Intertropical Convergence Zone explains intervals of speleothem deposition at Naracoorte (and would therefore have implications for the Nullarbor), but wider antipodean evidence lends little support to this mechanism.

Key words: Nullarbor, speleothems, climate change

Naracoorte,

Email: p.williams@auckland.ac

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

THE NULLARBOR - FLAT BUT FAR FROM BORING J. Webb^ ^ Environmental Geoscience Latrobe University The Nullarbor Plain is a very large continuous area of limestone (--'200,000 km^) distinguished by its flatness; it has the longest stretch of straight railway in the world (478 km). It slopes very gently seawards to terminate abruptly in a cliff-line that falls sheer into the sea except where there are coastal plains. The Nullarbor has an arid climate with low rainfall and high evaporation, and is mostly treeless and virtually uninhabited; there are no permanent streams. Its name, which means 'no trees' in Latin, was coined in 1867 by Delisser. To some people, the Nullarbor represents the most monotonous landscape in the world; the Ooldea Range on the northeastern edge of the Nullarbor has a dizzying 100 m of relief. Flinders, who mapped the coast in 1802, was perplexed by the extraordinary uniformity of the cliffs. The plain was not crossed until Eyre's trip in 1841, looking for grazing land, and by 1871 some sheep stations had been established. Probably the most exciting event to affect the Nullarbor was the nuclear testing at Maralinga to the north between 1956 and 1963. The Nullarbor was originally inhabited by the Miming tribe, who lived mostly along the coast, and used rockholes to trap and store water. Their stone tools were made from flint nodules weathering out of the limestone; extensive quarrying for flint occurred deep underground in Koonalda Cave for at least 16,000 years. Missions were established at Ooldea and Yalata for aborigines from the Nullarbor and surrounding areas, and are still small settlements today. Daisy Bates, who devoted 40 years of her life to studying aboriginal history and culture, lived in a tent at Ooldea until 1933. She was distinguished by her work for aboriginal welfare, financed from her own income, her strict lifelong adherence to Edwardian fashion, including boots, gloves and a veil, and her brief marriage to Breaker Morant. The Nullarbor is composed of three flat-lying limestone units that form part of the southern

Australian Tertiary limestone province, which is the largest area of temperate water limestone in the world. The oldest limestone is the Middle-Late Eocene Wilson Bluff Limestone, deposited across the entire Nullarbor in relatively quiet, shallow, cool temperate waters, and composed mainly of bryozoan fragments and forams. At this time the climate of the area was warm with a strongly seasonal rainfall; monsoon woodland (similar to that in northern Australia today) covered the hills north of the Nullarbor, and rainforest grew along the watercourses. In the Early Oligocene the sea withdrew from the Nullarbor, and the surface of the Wilson Bluff Limestone was exposed to weathering and erosion for probably 10 million years, forming a prominent surface soil and calcrete layer. From the Late Oligocene to Early Miocene, the sea returned and deposited the 100 meter thick Abrakurrie Limestone in the central Nullarbor area. The sea retreated and returned in the Middle Miocene to deposit the relatively thin Nullarbor Limestone, which contains abundant red algae and occasional patches of corals (although no reefs). The sea then withdrew, due to both eustatic sea-level fall and a period of uplift, probably in the late Miocene - Pliocene. The most spectacular features of the Nullarbor are its dolines and caves. Cave exploration dates back to the 1930's, and most of the large caves were located by the 1960's. Since 2000 detailed systematic surveys have been carried out during expeditions organised by the Victorian Speleological Association Inc. using an ultralight aircraft; these have discovered large numbers of small caves and a few larger caves. The numbers of large karst features on the Nullarbor are rather small: --150 collapse dolines (steep-sided, closed depressions up to 35 m deep and 240 m across) and --100 caves with significant passage lengths, present mostly within 60 km of the coast.

The lack of large caves has been attributed to the current arid climate ("retardation by drought"), but the caves formed under past wetter climates, and instead the flatness of the plain and the high primary porosity of the limestone caused the low level of karst development. The large caves extend 50-120 m below the surface of the plain; some reach the water table and contain lakes of clear, salty water, which approaches seawater salinity close to the coast. The water-filled passages, which extend over 6.5 km in Cocklebiddy Cave, provide wonderful cave-diving that has attracted divers from around the world. Most of the large caves are characterized by extensive collapse, forming passages with flat, bedding plane roofs and rubble floors; the biggest is the main hall of Abrakurrie Cave, which is 300 m by 30 m and 15m high. However, Old Homestead Cave, which is the northernmost of the large caves, shows the original passage form not affected by collapse; it consists of --30 km of jointcontrolled horizontal phreatic passages with large-scale wall scalloping and spongework developed on two levels, - 6 3 m and --70 m below the plain. The cave formed where water sank into the porous limestone at the termination of an old river course, now evident as a channel on the surface of the plain that extends northwards into the hills. The original passages of the deep caves closer to the coast were probably similar, and most likely developed when the sea retreated for 10 m.y. in the Oligocene; the warm wet climate of the time supplied abundant runoff, forming large trunk passages at considerable depth due to the very long flow paths (100 km or more). The passages probably collapsed when they were drained following uplift of the plain. The shallow caves in the south of the Nullarbor are mostly low collapse chambers and generally <30 m deep. Very dark brown, sometimes almost black calcite stalactites, stalagmites, and flowstone are common in many of the shallow caves; the Nullarbor Plain is the only area in Australia where calcite decoration of this color is so

abundant. The dark brown calcite was deposited predominantly during a wet climatic phase around 5 - 3 Ma; this interrupted an otherwise uniform trend of increasing aridity. Apart from the larger caves, the Nullarbor also contains thousands of blowholes, subcircular vertical shafts up to 1-2 m in diameter; the strong draughts blowing from many of the blowholes indicate that they connect to extensive shallow cave systems of small passages. These shallow caves are relict phreatic features; their entrances (blowholes) were opened as the land surface was lowered by denudation. Blowholes and associated caves are concentrated in a 25-30 km wide band located - 7 5 km inland, which marks the Late Miocene (~6 Ma) shoreline across the Nullarbor. The caves formed in the zone of enhanced dissolution at the seaward margin of the freshwater lens along the carbonate coastline. Cave development stopped when the sea retreated in the Late Miocene-Early Pliocene due to uplift and eustatic sea level fall. The tectonism that uplifted the Nullarbor Plain tilted it gently seaward and towards the east, and probably corresponds with the Kosciusko Uplift in SE Australia, which caused up to 600 m of uplift in eastern Victoria. Apart from speleothems, some Nullarbor caves contain very well preserved remains of extinct animals that roamed the area when the climate was wetter, like the marsupial lion and the Tasmanian tiger. Three pit-trap caves with abundant fossils of extinct megafauna were discovered in 2002. Overall, the Nullarbor is a fascinating place, particularly in terms of its depositional and climate history. These unique and interesting features should have been sufficient for the Nullarbor to gain nomination for World Heritage listing. Even the landscape grows on you, to the extent that regular visitors regard it as subtle rather than boring.

Email: john.webb@latrobe.edu.au

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

ADVANCES IN UNDERSTANDING THE EVOLUTION OF THE EUCLA BASIN OVER THE PAST DECADE J. D. A. Clarke^ U s Michell St, Monash ACT 2904 The Nullarbor Plain is the geomorphic expression of the carbonate rocks of the Euda Basin. However the Basin extends far beyond the limits of the Nullarbor. In the past decade there have been a number of advances in the understanding of the stratigraphy and sedimentary evolution of the Eucia Basin, in particular with respect to the basin margins and the post-Miocene succession, recognising some unique sedimentary fades and a new mineral province. While the main limestone-dominant part of the Euda Basin is confined to Nullarbor region, coeval marginal deposits extend west far as Denmark east as far as the central Eyre Peninsula. The Eocene marginal units consist of spiculites and spongolites probably deposited in in slightly freshened and acidified embayments and lagoons with stratified tannin-stained waters. A modern analogue is provided by Bathurst harbour in Tasmania. These passed abruptly into normal cool-water carbonate fades. Very large strandlines complexes developed during the two main Eocene transgressions, forming the Ooldea and Barton ranges. These strandlines host major mineral sand deposits, derived from the Musgrave block to the north. Miocene shorelines are less extensive, probably through a combination of lower sea level and more limited sand supply. An inferred Miocene strandline complex is none the less present in the south eastern Euda Basin. The strandlines and associated deposits form delimit the Eocene and Miocene transgressions and allow determination of the subsequent neotectonic tilting. The terminal Eocene (Tuketja) transgression reached -310 m elevation in the northwest (Cundeelee) but only 70 m in the east (Pinjarra Lakes) and - 3 0 m in the south (Point Culver), pointing to a gentle basinscale tilt to the southeast post-Eocene over a distance of-1100 km.

The development of Nullarbor Plain, the largest areal karst on Earth, occurred postMiddle Miocene with at least 14 My of exposure in changing terrestrial environments. Four phases have been recognised; 1) Diagenesis under a humid (Middle Miocene) climate with rapid mineral equilibration, cementation, extensive karst development, including development of flank margin caves in Late Miocene during stillstand in the marine regression and widespread lacustrine and palustrine sedimentation including ooids, now mostly preserved in karst cavities. 2) Latest Miocene to Middle Pliocene diagenesis occurred during a prolonged period ( - 8 m.y.) of temperate climate and resulted in initial deep cave dissolution during low sea levels and later shallow cave development in the course of a high sea level. 3) Increased aridity in latest Pliocene led to development of the modern landscape with solution pits, black limestone pebbles, open and closed dolines with associated colluvium fill, and pervasive accretionary pedogenic calcrete. The Roe Calcarenite represents the final phase of on-shore marine deposition in the Nullarbor region. High sea levels in the Early Pliocene led to 85 km of landward erosion in - 3 My and formation of sea cliffs of the Hampton Range. Quartzose mollusc grainstones-rudstones were deposited on a counterpart of the modern shelf. Presence of large foraminifera, grazing gastropods and coralline algae point to a seagrass bank. Work on the stratigraphy of the region is ongoing. Seismic data was acquired by Geoscience Australia and GSWA in 2012 which, although focussing on basement structure, suggested significant basement topography beneath the Nullarbor. Much remains to be done, especially on the deposition and diagenesis of the Eocene carbonates and subsurface basin architecture.

Key words: Nullarbor, Eocene, Miocene, Pliocene sedimentology, stratigraphy, diagenesis, karst Email: jon.clarke@bigpond.com

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

NULLARBOR SPELEOGENESIS: CONSTRAINTS FROM U-PB GEOCHRONOLOGY J.D. Woodhead 1 ^School of Earth Sciences, University of Melbourne, VIC 3010, Australia Australia's vast Nullarbor karst hosts some of the most enigmatic speleothems known worldwide. Not only are they often extremely dark coloured, suggesting a high organic content, but they have remained largely intractable to radiometric dating, lying beyond the range of the commonly employed U-Th chronometer i.e >600 ka years. Recent advances have, however, demonstrated the great potential of the U-Pb decay scheme to provide reliable ages for older speleothems in the range -400 ka to many millions of years. In a concerted research program extending over many years we have now obtained radiometric U-Pb ages for a large number of Nullarbor speleothems sourced from 22 caves encompassing a wide geographic area of over 100,000 km^. The samples document an extensive period of speleogenesis over the past 10 million years and are providing remarkable new insights into the climate and tectonic evolution of southern Australia throughout the late Neogene.

If viewed as a broad proxy for mean effective precipitation, speleothem age distributions suggest a peak 'wet' in the mid Pliocene around 4 Ma and document Australia's dramatic decline into aridity seemingly coincident with the intensification of northern hemisphere glaciation at -2.7 Ma. Decreased speleothem abundances prior to - 6 Ma may be partially influenced by sampling biases but, in concert with other proxy data, do hint at a potentially drier early Pliocene. The geographic distribution of speleothem ages reveals a trend of increasing ages in passing further north, potentially providing constraints on the rate of tectonic uplift of the Nullarbor Plain. Age distributions from within individual caves provide valuable new insights into the longevity of shallow caves within karst landscapes. The new radiometric ages provide a springboard for further detailed speleothembased studies of Neogene palaeoclimate and karst evolution.

Key words: Nullarbor, speleothem, U-Pb, palaeoclimate, tectonics Email: jdwood@unimelb.edu.au

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

LATE QUATERNARY SPELEOTHEM GEOCHRONOLOGY OF THE NULLARBOR PLAIN J. C. Hellstrom 1 ^School of Earth Sciences, The University of Melbourne, VIC 3010 Australia From the earliest attempts to date them (Goede et al., 1990; Sesiano and Hedley, 1996), it has been clear that the speleothems of the Nullarbor Plain are of great antiquity and almost entirely beyond the upper limits of the uranium-thorium (UTh) dating technique. Intensive use of the uranium-lead (U-Pb) dating technique (Woodhead et al., 2006) confirms this, finding widespread speleothem growth during the late Tertiary period and almost none in the Quaternary. By targeting the stratigraphically youngest speleothems for U-Th dating a small number of examples of late Quaternary growth have been discovered, presumed to represent relatively less arid intervals spread over the last 500,000 years. poo

U-Th dating uses disequilibrium in the U234u_230j|^ decay chain to accurately measure time since growth or deposition of speleothems and other (usually) carbonate materials (Richards and Dorale, 2003). Since the time when Nullarbor speleothems were first investigated using this technique analytical technologies have greatly improved, meaning that we now require around 10,000 times less material for an age determination and its upper age limit has moved from -350,000 years to 550,000 years or more. The relatively high uranium content of calcite speleothems beneath the Nullarbor, of several parts per million, means that U-Th dating can be applied to samples of as little as 1 mg. As such thin crusts and coralloid growths can be dated in addition to larger speleothems such as stalagmites and flowstones, and it is these former materials that represent much of the observed late Quaternary calcite deposition. Evaporitic speleothems of gypsum and halite have been previously reported from the Nullarbor (Goede et al., 1990; Lowry, 1967), and may comprise half or more of late Quaternary growth. Both are difficult to date by U-Th due to very low U content, of less than 1 part per billion (ppb) in the case of

halite and typically several ppb for gypsum. Relatively low solubility of these minerals in the acids used for U-Th sample preparation restricts the amount of material that can be used, subject to ongoing development of technique. Currently, evaporite speleothems are known to have formed over the last 100,000 years and are suspected to exceed 500,000 years in some cases. An important use of late Quaternary speleothems in general is in the dating of sub-fossil vertebrate deposits. The large and diverse megafaunal assemblages which are exceptionally well-preserved in a small number of Nullarbor caves have proved very difficult to date, but in some cases have a close or direct association with speleothem material. This has allowed the determination of a likely minimum age of 390,000 years for the megafaunal remains of Leana's Breath Cave, including the extinct marsupial lion Thylacoleo carnifex (Prideaux et al., 2007). Figure 1 shows the age distribution of calcite and evaporitic Nullarbor speleothems dated at the University of Melbourne and found to have formed over the last 500,000 years. They have no clear temporal relationship to global climate represented by the LR04 benthic isotope stack (Lisiecki and Raymo, 2005), although this could simply be due to the low number of samples which have been identified so far. Active drip-water infiltration into Nullarbor caves, required for any form of speleothem growth, is currently very rare. One such example found in the collapsing entrance to a cave a few metres beneath a dry watercourse has lead to still-active speleothem growth covering the last 3,000 years at that location. Further fieldwork and ongoing improvement of analytical techniques and technologies will lead to the identification of more Nullarbor speleothems in the Late Quaternary, but the story is likely to remain one of episodic, limited episodes of minor growth. These contrast with the rich, widespread assemblage of often massive speleothems now known to be of Tertiary

age and emphasized the difference in aridity

there between these times.

5 o "o s £

100

200

300

400

Age (ka)

Figure 1. Age histogram showing the distribution of identified speleothem growth relative to global climate over the last 500,000 years References Goede, A., Harmon, R.S., Atkinson, T.C., Rowe, P.J., 1990. Pleistocene climatic change in Southern Australia and its effect on speleothem deposition in some Nullarbor caves. J. Quaternary Sci. 5: 29-38. Lisiecki, L.E., Raymo, M.E., 2005. A Pliocene-Pleistocene stack of 57 globally distributed benthic delta 0-18 records. Paleoceanography 20: PA1003. Lowry, D.C., 1967. Halite speleothems from the Nullarbor Plain, Western Australia. Helictite 6: 14-20. Prideaux, G.J., Long, J.A., Ayliffe, L., Hellstrom, J., Pillans, B., Boles, W.E., Hutchinson, M.N., Roberts, R., Cupper, M., Arnold, L.J., Devine, P.D., Warburton, N.M., 2007. An arid-adapted middle Pleistocene

vertebrate fauna from south-central Australia. Nature 445: 422-425. Richards, D., Dorale, J., 2003. Uraniumseries chronology and environmental applications of speleothems. Reviews in Mineralogy and Geochemistry 52: 407-460. Sesiano, J., Hedley, I., 1996. Preliminary datation by palaeomagnetism of a speleothem in Nullarbor Plain, Southern Australia. Arch Sci C R Seances Soc 49:127-136. Woodhead, J.D., Hellstrom, J., Maas, R., Drysdale, R.N., Zanchetta, G., Devine, P., Taylor, E., 2006. U-Pb geochronology of speleothems by MC-ICPMS. Quaternary Geochronology 1: 208-221.

Key words: Nullarbor Caves, Uranium-thorium dating, Evaporitic speleothems. Quaternary aridity Email: j.hellstrom@unimelb.edu.au

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

STABLE OXYGEN AND CARBON ISOTOPE RECORDS FROM NULLARBOR SPELEOTHEMS R.N. Drysdale^ ^School of Geography, The University of Melbourne, Parkville Victoria 3010, Australia The Nullarbor Plain hosts a large number of well-decorated cave systems in which speleothem growth either no longer occurs or is restricted principally to odd patches of evaporite deposition. Recent radiometric dating by the speleothem research group at the University of Melbourne show that most of this speleothem growth occurred during the Pliocene epoch, a period widely regarded as a potential analogue for future global warming. Nullarbor speleothems thus offer a rare opportunity to explore the intricacies of Pliocene palaeoclimate from a Southern Hemisphere continental setting. The stable isotopes of carbon (^^C/^^C) and oxygen are the most common sources of proxy data in speleothem research, capable of providing information on past hydrological conditions.

temperatures and vegetation activity above a cave system. In this presentation, we trace the evolution of Nullarbor speleothem stable isotope patterns into, through and beyond the Pliocene and explore the likely prevailing palaeoclimate and palaeoenvironmental conditions. Using a combination of stable isotopes and other proxy data (organic fluorescence and trace elements), we also investigate the potential for uncovering highresolution records from the region using some of the longer, better-preserved stalagmites to provide insights on the character of intra-annual to decadal climate variability. Such data could potentially help validate climate-model simulations for the Pliocene that invoke a persistence of specific climate modes (e.g. ENSO) during this time.

Key words: stable isotopes, speleothems, southern Australia, Pliocene, palaeoclimate Email: rnd@unimelb.edu.au

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

LATE NEOCENE VEGETATION AND CLIMATE HISTORY OF THE NULLARBOR PLAIN: NEW INSICHTS FROM FOSSIL POLLEN RECORDS OF U-PB-DATED SPELEOTHEMS J.M.K. Sniderman^ ^School of Earth Sciences, University of Melbourne The Late Neogene environmental history of Australia remains poorly understood, because aridity has destroyed most fossil evidence of the aridification process itself; and because estimation of the ages of late Cenozoic Australian terrestrial fossil assemblages almost always relies heavily on far-field biostratigraphy, which is imprecise and may be inaccurate. Today, the semi-arid karst Nullarbor Plain separates mesic biotas of the well-watered southeast and southwest of Australia. Establishment of this biogeographic barrier has often been attributed to the late Miocene emergence of the Nullarbor marine limestone, since which time the Nullarbor is thought to have experienced a more or less continuously arid climate. However, pollen records recovered from U-Pb dated Nullarbor speleothems reveal a dynamic late Neogene vegetation and climate history. Latest Miocene pollen assemblages (dominated by Gyrostemonaceae, Casuarinaceae, Glischrocaryon) imply very open vegetation

under a semi-arid climate, yet the Chenopodiaceae shrubland which today dominates the Nullarbor Plain was absent. After -4.9 Ma, this vegetation gave way to forest assemblages dominated by Eucalyptus and Banksia with annual and summer rainfall increasing several-fold towards the Zanclean/Piacenzian boundary around 3.5 Ma. These results indicate that the Nullarbor was occupied by a mesic forest biome for at least --1.5 Myr of the Pliocene, potentially allowing the mingling of related, but now isolated, eastern and western Australian plant and animal clades. The modern arid climate and chenopoddominated vegetation of the region did not arise until the Pleistocene. The recovery of fossil pollen from U-Pb dated speleothems provides evidence independent of biostratigraphic inference, and represents a novel approach to the development of environmental and palaeoclimatic histories from currently arid regions which have poor fossil records.

Key words: speleothem palynology; Australia; palaeoclimate; vegetation history; pollen Email: kale.sniderman@unimelb.edu.au

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

MILLION-YEAR MENAGERIE: THE THYLACOLEO CAVES FOSSIL FAUNA E. R. Shute 1 V h D Candidate, Flinders University, Adelaide, South Australia In 2002, three limestone caves were discovered on the Nullarbor Plain in Western Australia. Collectively known as the Thylacoleo Caves, they offer an unprecedented window on the Early and Middle Pleistocene ecology of the Nullarbor. They have yielded some of the bestpreserved remains of extinct marsupial megafauna, including the first complete articulated skeletons of the predator Thylacoleo carnlfex (the 'marsupial lion'), various large-bodied herbivores including surprisingly - two new species of treekangaroo, and assorted smaller fauna. The locality is of enormous scientific value because it helps us to fill in a spatial and temporal gap in our understanding of the Pleistocene ecology of southern Australia. It has commonly been believed that the Nullarbor dried out 'about a million years ago' leading to the loss of trees, the rise of the modern salt-bush/blue-bush dominated landscape, and the development of this region as a major biogeographical barrier in

southern Australia. However, the fossil fauna strongly suggests the presence of a wooded landscape in the region within the last few hundred-thousand years, but apparently without higher rainfall than today (Prideaux et al. 2007). It seems that the Pleistocene ecological history of southern Australia is more complex and more interesting than previously envisaged, and the processes of change remain to be determined. Further excavations of the Thylacoleo Caves have been carried out in the last few years, with the aim of reconstructing ecological change on the Nullarbor over a longer period of time. Attention has also turned to some of the smaller fauna, especially the birds. Although the bird fossils initially seemed fairly unremarkable, recent excavations have revealed possibly the most diverse fossil avifauna in Australia, with more than 40 species identified to date, about 10% of which are newly-discovered species, and some of which have no modern representatives in southern Australia.

Key words: fossils, megafauna, vertebrates, birds, biogeography, Thylacoleo Caves Email: elen.shute@gmail.com

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

SHALLOW CAVES AND BLOWHOLES ON THE NULLARBOR PLAIN, AUSTRALIA — FLANK MARGIN CAVES ON A LOW GRADIENT LIMESTONE PLATFORM. S. Burnett.1 ^ Environmental Geoscience, La Trobe University, Victoria 3086, Australia The Nullarbor Plain of southern Australia is a very extensive limestone platform with relatively few large caves for its size, but contains thousands of blowholes, subcircular vertical shafts up to 1 - 2 m in diameter, which often connect to similarsized sub-horizontal passages. Historical karst exploration on the Nullarbor Plain has revealed a coastal karst band that extends - 6 0 km inland from the coast (although most features are within 25 km of the coastal scarp), and contains almost all the deep caves and collapse dolines (Fig. 1a). This coastal band has a maximum cave density of <20/25 km^, even when large caves and collapse dolines as well a substantial number of shallow caves and blowholes are included. Recent detailed systematic surveys of large areas of the Nullarbor Plain have provided new distribution data showing that blowholes and associated shallow caves are more highly concentrated in a second band that is 25-30 km-wide band located >75 km inland (Figs 1, 2a, b). The known density of these features (up to 43/25 km^) underestimates the cave porosity because the strong draughts blowing from many of the blowholes indicate that they perhaps connect to extensive cave systems of small un-enterable passages. These shallow caves generally lack speleothems and are relict phreatic features as they lie above the current watertable; their entrances (blowholes) were opened as the land surface was lowered by relatively uniform denudation. The blowholes are distributed independently of the low relief bedrock ridge/swale pattern that characterises much of the surface of the Nullarbor. They are

mostly located on the slopes of the ridges, but only because the intervening swales are often covered with a thin layer of sediment. This band of blowholes and caves is located along the Late Miocene (~6 Ma) shoreline across the Nullarbor, when there was a eustatic stillstand. The caves formed in the zone of enhanced dissolution at the seaward margin of the freshwater lens along the coastline at this time, and can therefore be regarded as flank margin caves on a low gradient limestone platform; a flank margin setting relatively unknown prior to this study. The width of the band of flank margin caves, which is substantially greater than previously documented for this cave type, reflects the very low gradient of both the ground surface and water table, together with the influence of tidal fluctuations and regression of the shoreline. The Nullarbor flank margin caves lack the larger chambers that characterise some flank margin caves, particularly in the Caribbean, because cave development stopped when the sea retreated rapidly in the Late Miocene-Early Pliocene due to a period of tilting and uplift. The band of flank margin caves has high permeability and substantial porosity, and would therefore form an excellent, largely overlooked, type of palaeokarst petroleum reservoir.

References Burnett, S., Webb, J. A., & White, S. (2013). Shallow caves and blowholes on the Nullarbor Plain, Australia—Flank margin caves on a low gradient limestone platform. Geomorphology, 201, 246-253.

Key words: Nullarbor Plain, Mixing corrosion. Flank margin caves. Blowholes, Australia Email: s4burnett@students.latrobe.edu.au

Figure 1 Overall distribution of known shallow caves and blowholes across the entire Nullarbor Plain.

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

Number of blowhotes and slaMo* caves per 5km^ Approximate hmtt of area of Wgh corvcentration

Figure 2a Shallow cave and blowhole distribution within the systematically searched areas in South Australia.

Number of Wowhoies and shallow cavfes per 5krm Approximate limit of area of high concentration

N Figure 2b Shallow cave and blowhole distribution within the systematically searched areas in Western Australia.

Selwyn Symposium 2014 University of Melbourne, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

UNDERWATER GEOLOGY AND GEOMORPHOLOGY OF THE SOUTHERN NULLARBOR. L . R o g e r s ^ & 1. L e w i s ^ ' ^ ^'Cave Divers Association of Australia, ^Latrobe University The first substantial publication about scientific investigations of the Nullarbor Plain Karst Sheet - "Caves of the Nullarbor" - was compiled nearly 50 years ago in 1967 by speleologists John Dunkley and Tom Wigley. It remains the only such comprehensive publication of its kind even now. One paragraph stated: "The linear arrangement of certain features on the Plain, and the proven ramifications of Mullamullang do suggest the possibility of very long deep caves along a fault or major joint .... Access to any such caves would probably be by extension of known caves,,,,,,,, plans are being made for a concentrated attack on the lakes of the deep caves. Such diving attempts have been made before without great success (e.g.Anon. 1963), but a well organised properly equipped expedition may well spearhead a new era of exploration in the caves of the Nullarbor." (Dunkley, 1967) This statement has proved prescient. Up until then most lakes were known but suitable scuba equipment had not become available to descend into them. In 1972 Ian Lewis organised the first cave diving expedition to the Nullarbor with six cave divers and approximately 30 cavers, discovering and exploring the vast tunnels of Weebubbie and Cocklebiddy Caves. The initial simple underwater maps were of great interest to Professor Joe Jennings at the Australian National University as they added significant new knowledge of Nullarbor cave development at times of lower sea levels, lan's second expedition with Keith Dekkers in 1974 dived in every other cave known to contain water using only basic equipment and recorded initial underwater dimensions for each. In the 40 years since, many highly-skilled and well-equipped cave divers have explored, mapped and photographed extensive submerged systems. Mapping under the Nullarbor in dark enclosed water is still difficult and demanding - hauling heavy

equipment to the water, finite air times, the restricted visual fields of dive masks, limited communication, monitoring of companions' safety, handling lengthy lines/tapes and recording underwater data on 'wetnotes'. Under the circumstances, excellent maps have been generated. For the future, lowpower LED lighting, pressure-proof lasers and multi-directional data recorders are an emerging cave diving technology. Most challenging of all has been the valiant endeavours of the cave diving photographers. Liz Rogers' father, Dr Peter Rogers, produced a distinguished and excellent record of the major underwater expeditions while at the same time managing the rigours of being a cutting-edge exploration diver. Undertaking that photography under extreme conditions was priceless - we owe almost our entire early breakthrough expedition record history to him. However, Liz has taken underwater cave diving photography in these conditions to an art form of global standard using sophisticated underwater cameras, LED lighting, slave flashes and Go-Pro camera technology. Liz's outstanding cave diving skills, multiple lighting placements and strategic approach to composition and setups for filming have elevated our capacity to interpret Nullarbor geomorphology, hydrogeology and microbiology The real advantages are the ability to examine her imagery conveniently later at leisure and in detail and to place her visual imagery alongside the underwater maps which can only record limited information within time constraints. Cave diver-mappers are not karst geomorphologists so it is the photography that records the underwater science. Liz's work reveals solution processes, passage morphologies, strata details, collapse patterns, subaerial processes now submerged and microbiotic life in the Nullarbor cave lakes unsuspected until diving began there.

Liz and Ian have teamed together as photographer and geomorphologist on several occasions to provide media footage of the Nullarbor lakes and submerged passages for various documentaries. Today's presentation will cover the scientific discoveries of the early underwater photography and Liz's excellent and entertaining modern work, fulfilling the prediction of John Dunkley and Tom Wigley nearly half a century ago.

References Anon 1963 Possible extension to Weebubbie Cave, Western Australia Helictite 1 (2): 6-7 Dunkley, J.R., 1967 The Geographical and Historical Background IN Dunkley, J.R. and Wigley, T.M.L. (eds) 1967 Caves of the Nullarbor; a review of speleological investigations in the Nullarbor Plain, Southern Australia. The Speleological Research Council Ltd, Sydney, p 10.

Key words: Nullarbor Plain, underwater caves, diving Emails: liz@photographyunderpressure.com; ian.lewis2@sa.gov.au

Selwyn Symposium 2014 University of Melbourne, October 3, 2014

Geological Society of Australia Abstracts XX The Nullarbor Plain: Recent Advances

THE ROLE OF TECTONICS ON THE DEEP CAVES ARRAY - A TEMPLATE FOR LARGE GLOBAL TERTIARY KARST AREAS. I. Lewis 1 Yatrobe University The Nullarbor Plain is the largest continuous karst sheet in the world. The limestone has not been altered by metamorphism due to the near absence of significant compressive tectonic influences. The Australian continent has three such large karst sheets, all positioned along its southern passive margin, of Tertiary age and cool carbonate origins - the Nullarbor, Murray Basin and Gambier Karstfields. Several similar karst sheets are found in the northern hemisphere in the Caribbean region. The Nullarbor is so large that it can contain all the others within it. In Australia, karst science studies of aspects of these large regional karst sheets have tended to focus on the hydrogeological processes, which develop the cave systems and the subsequent micro-processes, which give the caves their individual characteristics. These approaches do not generally address the reasons for the inception of the initial karst features nor explain their location and orientation. An exception to this is the flank margin speleogenesis (Burnett et al 2013), which however does not really address the issues of the large caves. An insight into the inception of major caves may provide clues to likely extensions of the systems, location of others and a broader view of the tectonic influences across the entire karst sheet. The karst sheets themselves are broad, shallow and relatively brittle on a crustal scale. An analytical advantage of such sheets is that the karst features contained within them can reflect the regional tectonics beneath, rather in the manner of a template. This can provide insights that would otherwise be unexpected or unrecognised by non-karst geologists. Effectively, large cave alignments are a subsurface 'etching' of transmitted tectonic weaknesses which have been exploited by water and are observable by cave mapping, while nearinvisible on the surface. As such, arrays of

larger caves in such karst sheets can be used to predict deeper tectonic influences at a local scale and extrapolated regionally if applicable. It is proposed that such analyses may allow large unmodified karst sheets to be a tool for interpreting basement tectonics. Recent studies have been undertaken in of one of these sheets, the Gambier Karstfield in southeastern South Australia, through analyses of cave distributions, orientation and alignments of major cave features at Naracoorte (Lewis et al 2006) and subsequently for deep cenote features at Mount Gambier (Webb et al, 2010). Initially apparent relatively random distributions of major caves have become clarified to revealed tectonic imprints ('up-printing'). Applying a similar approach to the other karst sheets in both hemispheres would be revealing and instructive for each region. More broadly, as karst science has generally been developed initially from vadose inputs on non-horizontal metamorphosed limestones, sheet karst structural analysis could provide a form of 'First Principles' to the body of theory on karst feature inception with large real-world examples. In this presentation, these approaches and techniques are applied to the Nullarbor Karstfield with particular reference to the large deep cave systems. Gentle low-angle tilting of the Nullarbor Karst Sheet to the southeast has been previously recognised but it can be expected that fracturing across the karst region has occurred during this process. Tectonic/Structural information about this region is limited as (to date) the region has not been of economic interest to the mining or oil and gas industries, groundwater quality is marginal and usage is minimal. An initial integration of the limited available structural sources is attempted. Some surface imagery has provided clues but it is proposed that in a similar way to the Gambier Karstfield, the large cave patterns

can provide substantial additional insight into their origins. Some other important associated influences are also briefly considered. This presentation is initial only as a formal program of work to investigate these issues has not yet been commenced. References:

Lewis, I.D, Lawrence, R & Mott, K., 2006 Origin and Genesis of the Major Caves at Naracoorte, South Australia, Helictite 39(2): 62-64 (extended abstract) Webb, J.A., Grimes, K.G. & Lewis, I.D. 2010 Volcanogenic origin of cenotes near Mount Gambier, southeastern South Australia, Geomorphology (1-2): 23-35.

Burnett, S., Webb, J. A. & White, S. 2013. Shallow caves and blowholes on the Nullarbor Plain, Australia - Flank margin caves on a low gradient limestone platform. Geomorphology, 201. 246-253. Keywords: Nullarbor, tectonics, deep cave systems, karstfield. Email: ian.lewis2@sa.gov.au

Selwyn Symposium 2014 University of Melboume, October 3, 2014 The Nullarbor Plain: Recent Advances

Geological Society of Australia Abstracts 111

NHL, WHU AND THE NULLARBOR PLAIN'S NATURAL HERITAGE VALUES S.White^'^ & G . A W a k e l i n - K i n g ^ Environmental Geoscience Latrobe University, ^ Wakelin Associates Pty Ltd A place may be widely known for its amazing natural features and yet be unprotected if its heritage status has not been established. Formal recognition of a place's geological heritage values occurs at the end of a process that is both administrative and conceptual. Recognition requires 1) that a scheme be in place, with administrative structures to ensure that it is transparent and consistent and its information securely archived, 2) that geoheritage assessment occurs, in which the place is assessed against the scheme's defined criteria and found to pass the significance thresholds, 3) that the assessment is documented, and that other papenA/ork is undertaken so the place and its assessment is brought to the notice of the scheme's administrators. The World Heritage List (WHL) is administered by UNESCO, and registers sites of outstanding importance to the common heritage of humanity. Before a site can be considered for WHL, its heritage value must first be registered in its own country. In Australia, the National Heritage List (NHL) is the register of places of outstanding heritage value to Australia. It encompasses natural, historic, and indigenous places. It has a defined set of criteria (Table 1), and places, which aspire to a National Heritage Listing must pass a significance threshold in at least one criterion. A significance threshold can be expressed in terms of the geographic area over which a site is notable. For example, a site of local significance may be important to an area of km radius, while a site of national significance is something that might be used as a reference site by the Australian geological community. The NHL threshold is that something must be outstandingly significant (significant to a national level). Geoheritage assessment looks at criteria required by the site registration scheme, and also considers other factors. In comparison with other places of similar type, is the site under assessment unusual on a national or a world scale? Does it have integrity (its key attributes intact and uncompromised) and

authenticity (its heritage values unambiguous and undisputed)? Does the site have added value by virtue of close association with another, different site, or because the single site expresses heritage attributes in different fields of geology? In this presentation we explore the Nullarbor Plain's attributes with respect to the NHL criteria (Table 2). The Nullarbor Plain's heritage encompasses not only its karst features, but also its distinctive Southern Ocean rocky coastline, including the spectacular Bunda Cliffs. The Nullarbor Karst One of the largest single karst areas in the world and the largest karst area in Australia, the 200,000 km2 Nullarbor Plain, is a flat, mostly treeless limestone plain. Limited surface solutional features are present and the caves are concentrated in at least two bands within 110 km of the coast (Burnett, et al, 2013). The solutional features consist of about 100 larger caves, > 150 collapse dolines and over 4000 smaller features generally blowholes and small shallow caves. Most caves are characterised by collapse. Some 20 larger caves reach the water table and have extensive flooded passages. The caves are thought to have formed during the wetter climates that predate the present aridity (Webb and James, 2006). A series of major conduits developed during warm seasonally wet conditions of the Oligocene; they drained after the Nullarbor karst was uplifted in the late Miocene, and collapsed to form large passages and dome chambers that retain the general cave orientation. The inland band of shallow caves and blowholes formed under phreatic conditions (Doerr et al., 2011) and represents the most intensive period of karstification recorded. It is parallel to the Eocene-Pliocene shorelines and lies approximately where the late Miocene (~6Ma) coast formed during a eustatic still stand (Hou, et al., 2008; Haq et al., 1987,1988). The caves appear to have formed in the enhanced dissolution zone at

the seaward margin of the freshwater lens along the karstic coast. (Burnett et al., 2013). During the warm wet period of the late Pliocene (--5-3 Ma ago) shallow caves developed calcite speleothems but as the climate reached its present level of aridity million years ago, evaporite (gypsum and halite) speleothems have formed as stalactites, columns, crusts, curving crystal clusters and hair-like helictites. In addition, salt crystallisation along cracks and within the pore spaces of the limestone and speleothems has wedged grains of limestone from the cave walls and roof, depositing these as sand on the cave floor, and breaking calcite speleothems into shards. This process of crystal wedging has probably caused some cave collapse and assisted in the development of the collapse dolines (Webb and James, 2006). Some speleothems are composed of dark brown to black calcite, which are at present being overgrown and broken down by halite crystallising in cracks. Since the uplift of the Nullarbor Plain, surface-weathering rates have been exceptionally low (2 to 5 mm/kyr), inhibited by the indurated surface calcrete layer and the overall semi-arid to arid climate. Little surface solution sculpture, relatively few caves and no solution dolines formed over this time, and the Nullarbor karst largely retained its flat depositional surface. A continuous line of cliffs, bluffs and escarpments occurs along or as the southern margin of the Nullarbor Plain, including the Bunda and the Baxter Cliffs. The Bunda Cliffs are one of the longest continuous cliffed coastline in Australia, extending 210 km from Head of the Bight in the east to Eucia in the west. The cliffs vary in height from 40 to 90 m. A landwards extension of lower bluffs continue inland as the Hampton Escarpment for another 300 km before reaching the coast again as the Baxter Cliffs that run for another 160 km to Point Culver. From here the cliff line strikes inland again as the Wylie escarpment. In all, the cliff line is 790 km long; the Bunda Cliff section being the longest and most spectacular. In addition to their remarkable length, the Bunda Cliffs expose the geological units of the Nullarbor karst (limestone) showing the upper reddish brown Nullarbor and Abrakurrie limestones and the lower white Wilson Bluff limestone. Cliff recession itself isn't a rare process, but the absence of subaerial down wearing of

the hinterland, the relatively soft nature of the limestone, and the exposure to strong southerly swell and storm waves result in an excellent example of marine processes driving rapid cliff recession. Geoheritage Significance of the Nullarbor Plain and the Bunda Cliffs. The values of heritage are diverse and subjective. However, many studies of geodiversity identify the same characteristics as being valuable: intrinsic, aesthetic, cultural, economic, scientific, and educational. It is important to be clear about the role of aesthetics in the geoheritage assessment, particularly the heritage of landscape. Some places of very high significance with respect to their geology and geomorphology may not be at all aesthetic, whereas extremely beautiful views often do not correspond to geological significance. While aesthetics may have played a role in the creation of national parks, it is only one of the nine NHL criteria. The aesthetic appreciation of a landscape is not a direct function of its geological values but is related to cultural aesthetic concepts. The geoheritage values of the Nullarbor have been assessed against the NHL criteria (Table 1) then compared with other similar places, according to degree of unusualness, integrity, and authenticity using the Earth Science Comparative Matrix (ESCoM) (White and Wakelin-King, 2014). This robust and repeatable semiquantitative Australia-wide comparative process overcomes many of the problems of previous assessments. The overall values of a site are quantified, leading to a qualitative judgement on whether it achieves the threshold of outstanding heritage value. In NHL assessment, in order to establish whether a place is of outstanding value to Australia, its values must be compared with other Australian places with similar values, and comparative information for the whole continent ( - 7.7 million km2 ) is therefore required. The Nullarbor Plain exceeds the NHL significance threshold in at least 5 of the 9 criteria. For 4 of those 5 criteria, the Nullarbor Plain exceeds the threshold for its karst features and again, separately, for its coastal features (Table 2). It is indeed a landscape of national significance. The valuable attributes of the Nullarbor Plain have been researched and documented by many individuals and

organisations e.g. Davey et al., 1992. The information exists in the scientific literature, in reports, and in the corporate memories of the speleological and research communities. Geoheritage assessment using the ESCoM was most recently undertaken (Wakelin-King and White, 2011).

and cycles of sea-level change. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G.St C., Posamentier, H.W., Ross, C.A., van Wagoner, J.C. (Eds.), Sea-level Changes, an Integrated Approach. Society of Economic Paleontologists and Mineralogists Special Publication. 42: 71-108.

It only remains to have the Nullarbor Plain nominated for its place on the National Heritage List! *

Hou, B., Frakes, L.A., Sandiford, M., Worrall, L., Keeling, J., Alley, N.F., 2008. Cenozoic Eucia Basin and associated palaeovalleys, southern Australia — climatic and tectonic influences on landscape evolution, sedimentation and heavy mineral accumulation. Sedimentary Geology. 203: 112-130.

References Burnett S., Webb J.A, White S., 2013 Shallow caves and blowholes on the Nullarbor Plain, Australia - flank margin caves on a low gradient limestone platform. Geomorphology \ 246-253. Davey, A.G., Gray, M.R., Grimes, K.G., Hamilton-Smith, E., James, J.M. and Spate, A.P., 1992. World Heritage significance of karst and other landforms in the Nullarbor region. Report to the Commonwealth Department of Arts, Sport, The Environment and Territories, Applied Ecology Research Group, University of Canberra, Canberra. Doerr, S.H., Davies, R.R., Lewis, A., Pilkington, G., Webb, J.A., Ackroyd, P.J., Bodger, O., 2011. Origin and karst geomorphological significance of the enigmatic Australian Nullarbor Plain 'blowholes'. Earth Surface Processes and Landforms. 37: 253-261. Haq, B.U., Hardenbol, J., Vail, P.R., 1987. The chronology of fluctuating sea level since the Jurassic. Science. 235: 1156-1167.

Wakelin-King, G.A. and White, S., 2011: Potential Geoheritage Values of Australian Desert Landscapes, A report to the Commonwealth. Department of Sustainability, Environment, Water, Population and Communities, Canberra. Webb, J.A., James, J.M., 2006. Karst evolution of the Nullarbor Plain, Australia. In: Harmon, R.S., Wicks, C. (Eds.), Perspectives on karst geomorphology, hydrology, and geochemistry—a tribute volume to Derek C. Ford and William B. White: Geological Society of America Special Paper 404. Geological Society of America, Boulder, Colorado: 65-78. White, S. and Wakelin-King, G.A., 2014. Earth Sciences Comparative Matrix: A Comparative Method for Geoheritage Assessment. Geographical Research 52(2): 168-181.

Haq, B.U., Hardenbol, J., Vail, P.R., 1988. Mesozoic and Cenozoic chronostratigraphy •

Nomination information is available online through the Heritage section of the Australian Department of the Environment (http://www.environment.gov.au/heritage). To place the Nullarbor Plains on the National Heritage register, interested persons must obtain a nomination form from the Australian Department of the Environment (http://www.environment.gov.au/topics/heritage/heritage-places/nominating-heritage-place). The nomination and its supporting information are submitted to the Department. From there it will be assessed by the Australian Heritage Council in a process that includes a period of public consultation (http://www.environment.gov.au/node/19600). All webpage references in this paragraph were accessed 2 Sept. 2014.

Table 1: The National Heritage criteria (criterion keywords in italics)

The place has heritage value to the nation because of its: NHL criteria

Criteria as applied to Australian karst

Importance in the course, or pattern, of Australia's natural or cultural history {events and processes)-,

Demonstration of the processes of karst formation or maintenance, or possession of geomorphic relics of significant earth events;

Possession of uncommon, rare or endangered aspects of Australia's natural or cultural history (rarity)]

Possession of rare, unusual or endangered karst landforms or processes;

Potential to yield information that will contribute Potential to further understanding of Australia's development through geological to an understanding of Australia's natural or cultural history (research)] time, or of Australia's characteristic karst features;

Importance in demonstrating the principal characteristics of: i) a class of Australia's natural or cultural places; or ii) a class of Australia's natural or cultural environments (principal characteristics)]

Importance in demonstrating the principal characteristics of karst landforms or processes;

Importance in exhibiting particular aesthetic characteristics valued by a community or cultural group (aesthetic)]

Importance in exhibiting the aesthetic value of the landscape, especially in an Australian context;

Importance in demonstrating a high degree of creative or technical achievement at a particular period (creative or technical);

Association of the karst features with a particular human achievement;

Strong or special association with a particular community or cultural group for social, cultural or spiritual reasons (social);

A place's geomorphology has strong or special association with the scientific or educational community, or has been most intensively investigated, or has a particular cultural impact;

Special association with the life or works of a person, or group of persons, of importance in Australia's natural or cultural history (significant person)]

Special association of karst landforms or landscapes with the works of a pioneering geologist, or a fundamental component of an artist's oeuvre;

Importance as part of Indigenous tradition (indigenous).

Indigenous use of karst features

Table 2: Main Geoheritage attributes of the Nuliarbor Plain's karst and coastal features, listed against NHL and other criteria. Nuliarbor Plain (karst) Bunda Cliffs (rocky coastline) Criteria NHL - Events and Cave distribution in bands; surface has very Cliff recession driven by strong Processes low relief: cave formation related to lithology coastal energy. Sharp cliff edges and sea level, little influence from jointing or and vertical faces: despite soft surface topography; salt weathering (crystal lithotype, lack of surface drainage in wedging), halocline corrosion, flank margin karst hinterland preserves land's edge during uplift. speleogenesis Long single-cliff coastline, very Extent of the karst area. Low relief and NHL-Rarity distinctive vegetation. Unusual evaporite uniform in character. Most speleothems. spectacular section of a very long coastal cliff NHL - Research Megafauna in cave deposits. Cave Uplift history of southern Australia, distribution relevant to sea level change and evolution of Australian plate. continental evolution. Speleothem dating Sedimentology of the Eucia Basin. and linking to climatic conditions. Datable interactions between deposition, sea level change, and uplift. An outstanding example of karst modified by An outstanding example of a waveNHL - Principle and storm-dominated coastline. characteristics of a increasing aridity. The largest known Tertiary karst area worldwide. Solutional class features: --100 larger caves, > 150 collapse dolines, >4000 blowholes, small shallow caves, speleothems, cave decoration, collapse structures. Outstanding flooded caves with rare microbiological 'slime' organisms. Visually spectacular rugged NHL-Aesthetics A stark and iconic Australian landscape. coastline. NHL - Creative or technical achievement Hostile coastline and stormy ocean NHL-Social Speleological community: collective selfshaped exploration and settlement organised and largely unrecompensed exploration and documentation by groups of patterns along the southern Australian coastline. EucIa has been individuals; liaising with the academic the only sea access between Fowlers research community. Bay and Israelite Bay (now disused) NHL-Significant Australian karst pioneer Joe Jennings. people NHL - Indigenous Aboriginal use of caves (NB this information needs consultation with relevant sources). One of the largest single karst areas in the Unusual (world) world. One of the longest single-cliff Unusual (Australia) Largest karst area in Australia. coastlines. Part of a continuous 790km long line of cliffs, bluffs and escarpments: combined palaeo- and modern cliff-line. Unaltered by human activity. Some pressures along the main highway, Integrity but relatively unaltered in most places. Yes Yes Authenticity