The Emu Bay Shale Konservat-Lagerstätte:
A view of Cambrian life from East Gondwana
Prof. John Paterson
School of Environmental and Rural Science, University of New England
The Cambrian Period (541 to 485 million years ago) is arguably the most important phase in the evolution of multicellular life. The event known as the Cambrian ‘explosion’ embodies the proliferation of marine organisms and the first appearance of most animal groups familiar to us today (e.g., arthropods and molluscs). Animals with preservable hard parts (e.g., shells), and those that could burrow into the sediment became increasingly abundant and forever changed the marine biosphere. This interval also heralds the Cambrian arms race, a period that amplified ecological complexity, including the advent of predator-prey relationships that completely re-shaped food webs within marine ecosystems. The early Cambrian (515 million-year-old) Emu Bay Shale on Kangaroo Island (South Australia) represents a site of exceptional fossil preservation, including soft tissues such as muscle and digestive glands. It provides a critical window into the Cambrian world by giving a glimpse of complete organisms and their communities, rather than the more common preferential preservation of hard parts in the fossil record. Excavations over the past 10 years have revealed that the Emu Bay Shale biota comprises over 50 species (to date), many of which are new to science and await documentation. This talk will focus on these exciting new discoveries.
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Speaker bio...
John R. Paterson is a Professor of Earth Sciences and currently an Australian Research Council Future Fellow at the University of New England (UNE) in Armidale, New South Wales. He graduated with a BSc (Hons) (2001) and PhD (2005) from Macquarie University in Sydney. He completed postdoctoral studies at the South Australian Museum, Adelaide (2005) and Macquarie University (2006) before his appointment as a Lecturer at UNE in 2007. His main research interests include Cambrian faunas from East Gondwana, especially the Emu Bay Shale Konservat-Lagerstätte of South Australia.
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He has served as Secretary of the Association of Australasian Palaeontologists (AAP; 2006-2010), is currently a corresponding member of the International Subcommission on Cambrian Stratigraphy, and serves on the editorial boards of the peer-reviewed journals Alcheringa, AAP Memoirs and Zootaxa. He was recently awarded the 2016 Anton Hales Medal by the Australian Academy of Science.
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Overview of the 2016 Selwyn Symposium
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An audience of over seventy local and interstate geologists attended this year’s one day Selwyn Symposium at Melbourne University to hear new, diverse evidence from eleven speakers on the assembly, fragmentation and breakup of East Gondwana.
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George Gibson from the ANU made a persuasive argument that gravity and aeromagnetic data shows that the Gondwana margin was strongly segmented and included hyperextended section bounded by transform faults. These features had an influence on the subsequent geometry of folding and thrusting in the Delamarian and Lachlan orogens. Andrew Merdith from the Earthbyte Group showed his deep time plate reconstructions to create a kinematically feasible model of the Rodinia-Gondwana transition. He has created a number of scenarios in order to gain insight into India’s position during 650-550Ma as there is no paleomagnetic data to help constrain the rifting time, angular rotation, spreading and convergence rates suggested by geological evidence. Steven Boger followed by taking us on an entertaining journey of his extensive fieldwork from Arabia to Antarctica. He argues that there is evidence, revealed by Sm-Nd isotope analysis, for a continuous north-south belt of juvenile intra-oceanic terranes which formed and coalesced within the Mozambique Ocean prior to the suturing of Gondwana.
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Alan Collins presenting his research on the tectonic geography of Gondwana
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After a short break we returned to hear Nick Rawlinson give us an update on results from the WOMBAT passive high density seismic data project to image the lithospheric structure beneath eastern Australia. This edge of the Australian plate has extensive Mesozoic and Cainozoic cover which masks the Palaeozoic basement and complicates the task of unravelling the tectonic evolution. Of particular interest were the latest results from ambient noise tomography which extends Nick’s earlier crustal azimuthal anisotropy model south across Bass Strait into Tasmania. He has discovered that in Bass Strait the fast axis of anisotropy is not aligned parallel to the rift zone as it would be in contemporary rifts but lies parallel to the palaeo-fracturing trend of the crust, which was created by Cretaceous extensional forces. This contrasts with the dominant N-S orientation of the anisotropy pattern of the mainland and Tasmania that correlates closely with the dominant geological fabric of the Palaeozoic orogens (a close match to the magnetic fabric), and is consistent with a prevailing direction of compression that was perpendicular to the proto-Pacific margin of Gondwana. Alan Collins from TRaX then gave us a broad view of the tectonic geography of Gondwana pieced together from evidence gathered from the chemistry of the detrital products of volcanic arcs now preserved, metamorphosed and deformed in the orogens of Madagascar, southern India and Arabia. Alan argues that to have a more precise understanding of the formation of Gondwana we need to understand the orogens along which it formed. These talks ignited some energetic discussion at lunch.
In the afternoon we heard from David Moore as he presented an aspect of his PhD thesis, the ribbon tectonics of Vandieland. Continental ribbons drifted north from East Antarctica until they began to interact with the subduction system outboard of east Gondwana around 520 Ma. These rocks are preserved in western Tasmania and David showed that rather than being subducted there is evidence of shortening found along the Bernie-Pedder boundary. Paul Green from Geotrack followed with a passionate argument for geologists to consider the importance of the ‘missing section’. He said ‘the gaps are more important than the record!’. Paul has spent over 30 years studying thermochronological data and has observed that episodes of exhumation during the breakup of Gondwana were proceeded by periods of subsidence and burial during which several kilometres of section were deposited before being removed. He has integrated AFTA and geological data of South Africa, Namibia, Angola, Gabon and Equatorial Guinea and has discovered that the continental margins of southern Africa underwent several episodes of pre-breakup exhumation. He has also observed multiple synchronous cooling events from 200Ma to 21Ma that occur along the West African margin to Brazil which show remarkable synchronicity. In particular, he has noted that a Late Cretaceous Campanian cooling event has affected much (onshore as well as offshore), if not all, of the region. He suggests that the presence of multiple discrete events may be caused by changes in external stresses – perhaps changes in plate motions, or more complex mantle dynamics. Finally we heard Hamish Campbell from GNS New Zealand make a humourous plea for the recognition of the continent of Zealandia. This continent formed during rifting in the Late Cretaceous. He made a case for the many ways Zealandia fits the definition of a continent (higher elevation of continental crust, thicker and lower seismic velocity, distinctive continental geology, large enough to be distinguished from a continental fragment and mostly surrounded by oceanic crust) and illustrated how this has had a useful outcome as it has helped to increase New Zealand’s maritime boundary. He also showed how orogenic belts, such as an early Palaeozoic greywacke belt, can be traced through Zealandia to both Australia and West Antarctica.
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Hamish Campbell with GSAV committee members, David Cantrill, Michelle Grosser, Barbara Wagstaff and Susan White, enjoying a break between sessions.
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The final session met after coffee,cake and rowdy discussion to examine Gondwana breakup. Simon Holford from the University of Adelaide presented on seismic through the basins of the southern Australian margin and provided an overview of the distribution, age and characteristics of the subsurface volcanic and intrusive features. He noted that evidence of Cretaceous volcanism has not been found west of the Bass Basin. He then discussed how these observations fit with proposed geodynamic models such as intraplate magmatism or edge driven convection. Milo Barham from Curtin University presented a provocative paper proposing that significant ash fall from the distal explosive super-eruptions during the Zealandia rifting event supplied the unique Albian detrital zircon population found in the Madura Formation. This population is identical in Hf-isotopic character to volcanic crystals from the Whitsunday siliceous large igneous province. He argues that a disconnect existed between the sediment routing systems operating in the eastern and western Bight Basin, with little or no sediment from the east being supplied from the west. Finally we heard from Ian Duddy who gave us a detailed argument of why passive margin development is much more complex than the simple subsidence model envisaged by the McKenzie (1978). He showed how the interior and continental margins of Australia have undergone multiple episodes of exhumation. Ian argues that the Late Jurassic Gondwana unconformity in Australia is being exposed by exhumation now and that any Gondwana surface that may have existed in the SE Highlands (even on the high summits of Kosciuszko) was removed by kilometre scale mid-Cretaceous exhumation. The massive scale of the Mid-Cretaceous exhumation has provided the sediment to the rapidly subsiding Late Cretaceous depocentres in the Gippsland, Otway and Bight Basins. Mid Cretaceous exhumation also extends northwards to Cobar-Milparinka, and beyond, with km-scale uplift and erosion recorded in wells along the Morney, Pepita, Jackson anticlines within the Eromanga Basin.
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John Webb receiving the Selwyn Medal from Ingrid Campbell.
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2016 Selwyn Medalist, John Webb, with a collection of former students.
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November Meeting Social Event
Monash Earth Sciences Garden
Thursday the 24th of November
The first of its kind in Australia and the most comprehensive worldwide, the Monash Earth Sciences Garden is inspired by the geology and geomorphology of Victoria, Australia. A textbook brought to life. The Monash Earth Sciences Garden comprises a stunning arrangement of nearly 500 rock specimens, weighing up to 14 tons, laid out to represent a pattern of rock outcrops and set amongst beautiful native plants representing each geographical region. Head of School, Earth, Atmosphere and Environment, Professor Sandy Cruden, who was part of the team of Earth Scientists who developed the Monash Earth Sciences Garden concept, said the Monash Earth Sciences Garden establishes a brand new, hands-on approach to teaching geology, physical geography and atmospheric sciences.
The final meeting of 2016 will be a tour of this wonderful garden including a lecture by their outreach geologists. Afterwards we will have drinks with the postgraduate students and then go on to a yum cha restaurant in Springvale to celebrate the end of the year.
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Student sponsorship
Maxwell Lechte
The University of Melbourne
William Smith was a 19th Century English geologist best known for his landmark geological map of the British Isles. The Geological Society of London inaugurated the William Smith Meeting in honour of his life and works, and these annual meetings cover all facets of geological research. The 2016 William Smith Meeting took place in June and covered ‘Glaciated Margins: The Sedimentary & Geophysical Archive’. I was lucky enough to be invited to speak at this meeting at the impressive and historic Burlington House building of the Geological Society of London, and to be granted the Student Research Scholarship from the GSAV in order to assist with funding my attendance at this conference.
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My research focuses on the glacial sedimentology of the ~700 Ma Sturtian glaciation, the older of the two archetypal ‘Snowball Earth’ glaciations, which potentially covered the entire planet and lasted for over 50 million years. The particular focus of my research pertains to unique and puzzling iron formations associated with the Sturtian glacial deposits. Since this is a global phenomenon, study of the Sturtian glaciation lends itself to wide-reaching field studies. My talk at the William Smith Meeting presented the results of field work conducted in South Australia and Namibia, including geological and geochemical evidence for a potential sub-ice setting for the deposition of iron formation during the Sturtian glacial event. Attendance at this meeting was important and insightful not only because it was attended by experts in the field of glacial sedimentology, offering a unique opportunity for networking, but also because it actively promoted a forum of constructive scientific discussion. I was able to meet with researchers who were knowledgeable on the issues surrounding the Sturtian glaciation, and who have worked on the exact same deposits in South Australia and Namibia, and whose insights were invaluable to my work. As such, I am extremely grateful for my chance to attend and present my work at the William Smith Meeting, and for the support of the GSAV.
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The internationally renowned monthly social get-together
for explorers, miners & other geoscientists
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Fellow Geoscientists,
Welcome to the inaugural GeoPub Melbourne. This monthly event provides an opportunity for members of the Melbourne exploration community to catch up on the industry “goss”, have a few drinks, talk technical, reminisce, and/or generally socialise. Occurring on the second Friday of the month, GeoPub Melbourne aims to become a regular event on any Geologist’s social calendar.
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INVITATION TO GEOPUB MELBOURNE
Join Us: At 5:30pm, every 2nd Friday of the month as your work-spouse-budget-health allows.
Why: Meet other people working / interested in geology, mining & exploration.
And Do? Catch up on "goss", have a few drinks, talk technical, reminisce, and/or generally socialise.
Where: P.J. O’Brien’s, Shop G12-16, Southgate, Southbank.
Contact: geopubmelb@gmail.com
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Forthcoming events
Unless otherwise noted, all 2016 talks will be held at the Fritz Loewe Theatre, School of Earth Sciences, University of Melbourne.
October 27th: Monthly meeting:
Associate Professor John Paterson:
The Emu Bay Shale Konservat-Lagerstätte: A view of Cambrian Life from East Gondwana
November 24th: Monthly meeting:
Social Night: Includes a tour of the Monash University Earth Science Garden, 500 rock specimens and Chinese feast in Springvale. Details above.
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Student Scholarships
The GSAV are pleased to offer scholarships for honours and postgraduate students in geological sciences for assistance with travel costs associated with attending conferences (fieldwork excluded). The number and value of the scholarships awarded each year is made at the discretion of the GSA Victoria committee. Up to $500 for travel within Australia and between Australia and New Zealand and $700 for travel elsewhere is available, paid half before and half after the conference. More information, including the eligibility criteria and application form, is available at http://www.gsavic.org/scholarship.html.
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Contributions to The Victorian Geologist
If there are any events, happenings, news, or views that would be of interest to the membership, please send your details and information to Kieran Iles at kiles@student.unimelb.edu.au
Newsletter deadline: First Friday of the month, except for December and January.
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Contribute to TAG
It is member contributions which make TAG (The Australian Geologist) a member magazine – please keep the contributions coming and assist with informing all of the membership (not just your Division) about your activities.
Please send your news to: tag@gsa.org.au
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About the GSA Victoria Division
General information about the Geological Society of Australia and GSA Victoria Division can be found at www.gsa.org.au and www.gsavic.org.
Contact details for the GSAV Committee can be found at www.gsavic.org/committee.html.
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