PALAEOCLIMATESMelbourne University, October 31, 2024
From 2pm onwards
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Registration (Symposium Registration and Dinner RSVP)
Symposium Registration
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Selwyn Dinner Registration
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Participants can also register on site on the day. Cash payment only. Detailed Program
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13.30 - 14.00
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Registration (coffee and tea available)
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14.00 - 14.05
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Dr. Anne-Marie Tosolini (GSAV Chair)
Symposium Opening |
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14.05 - 14.30
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Dr. Ashleigh Hood, Sedimentology (University of Melbourne)
The Cryogenian glaciations: A snowball Earth or a dynamic ice age? AbSTRACT
The early Cryogenian Sturtian glaciation is likely the most extreme ice age in Earth’s history. Over 55 million years in duration, this extensive glaciation poses a challenge for the survival of the life. The Sturtian succession of the Flinders Ranges, South Australia, is exceptionally preserved and hosts several kilometres of glacial stratigraphy, providing a window into Cryogenian glacio-marine environments. Newly measured sections record several intervals of glaciation, and at least one significant unconformity. Our research shows that the sedimentology and geochemistry of these glacial units show evidence for less severe glacial conditions than previously emphasized. Authigenic dolomite is present through the Sturtian glacial stratigraphy in many locations, and has sedimentological and geochemical characteristics of precipitation from syn-glacial seawater. Through modelling work, the presence of carbonate precipitates in the glacial units implies that continental weathering and the hydrological cycle did continue through the ice age, though they were severely dampened. Further, we use ASTER imagery combined with stratigraphy and geochemistry to show that the Sturtian glaciation in the northern and central Flinders Ranges can be divided into at least two distinct glacial intervals separated by unconformities, and in some areas includes an interglacial period. This boundary can be marked by the Warcowie Dolomite Member of the Wilyerpa Formation, a laminated dolomite or dropstone-rich dolomite unit which may be up to 20m thick and strongly resembles a post-glacial ‘cap carbonate’. Where preserved, the sediments which overlie this unit may include several hundred metres of siltstones with no evidence for glaciation, and may onlap structures in the underlying glacial sediments. This research improves regional stratigraphic correlations and adds to growing evidence for a more dynamic and complex Sturtian glaciation than previously recognised, with a significant mid-glacial ice-free interval. bIO
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14.30 - 14.55
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Dr. Vera Korasidis, Palynology (University of Melbourne)
New palynological insights on the Paleocene Eocene Thermal Maximum AbSTRACT
To better understand the effect of the Paleocene-Eocene Thermal Maximum (PETM) on continental ecosystems, we studied new palynological samples from the Bighorn Basin (BHB), northwestern Wyoming, USA. We see palm and fern abundances increase in the last 20–40 ka of the Paleocene, then dramatically with the onset of the carbon isotope excursion (CIE) defining the base of the PETM. Palynomorphs of plant groups with modern temperate climate distributions are absent from the CIE body, and this is when tropical plants are most diverse and abundant. During the CIE recovery, pollen of mesophytic/wetland plants become more common while tropical taxa persist. In the post-CIE early Eocene tropical taxa are rare and temperate forms abundant, similar to the late but not latest Paleocene. We interpret palynofloral changes to indicate warming in the latest Paleocene, rapid warming and drying with the CIE onset, dry tropical climates through the CIE body, a return to wetter floodplains during a very warm CIE recovery, and cooler wet conditions in the post-PETM early Eocene. These rapid, climatically forced changes in floral composition occurred without major extinction, perhaps indicating nearby refugia in which plants adapted to cooler and wetter climates persisted through the PETM. We also examined possible changes in pollination mode during the PETM as inferred from three lines of evidence: the prevalence of fossil pollen preserved as clumps, the pollination mode of nearest living relatives (NLR) and angiosperm pollen morphological diversity. All three suggest animal pollination became more common and wind pollination less common during the PETM. The decrease in wind pollination during the PETM reflects the basin-scale extirpation of wind-pollinated lineages, and their replacement by dominantly animal-pollinated lineages due to rapid warming and drying. The hotter and more seasonally dry climates not only facilitated the northward range shift of plant taxa, but also their insect and/or vertebrate pollinators. bIO
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14.55 - 15.20
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Dr. Andrew Gunn, Geomorphology (Monash University)
Climate memory in giant dunes AbSTRACT
Dune morphology and stratigraphy typically expresses local wind climate. As dunes grow, however, the time it would take for morphology to adjust and represent a new wind climate grows. Climate changes on timescales similar to this dune readjustment timescale on Earth. This overlap in timescales may mean that some dunes on Earth’s surface have morphologies which are consistent with modern climate, and others don’t. Here we employ topography and climate data to quantify the timescales of dune readjustment and climate persistence for the Rub' al Khali. We find a diversity of cases: some where climate has been remarkably consistent through the glacial cycles, some where climate has changed but dune morphology has equilibrated to modern climate, and some where dune morphology represents an old climate and not modern climate. These results are synthesized in a framework that allows us to delineate the size below which dune morphology represents modern climate, and above which it still remembers a different past climate. bIO
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15.20 - 15.45
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Afternoon tea break (coffee, tea and snacks available)
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15.45 - 16.10
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Tim Ziegler, Vertebrate Palaeontology (Collections Manager - Melbourne Museum)
A new Pleistocene vertebrate fossil locality informing palaeoenvironment and ecology in subaerial Naarm (Port Phillip) AbSTRACT
The Werribee Fan is a newly recognised, diverse vertebrate fossil deposit from an outcropping of the Pleistocene Deutgam Silt near Cocoroc, Victoria. This local fauna differs markedly in its patterns of abundance and correlation from proximal fossil localities at Keilor, Lancefield, and the Western District Lakes. The dominance of browsing marsupials, particularly among the largest taxa, is suggestive of a heretofore unobserved habitat or depositional context for a southern Victorian fossil site. Taphonomic evidence supports a model of deposition within an oxygenated, low-energy terrestrial subaquatic environment. The Werribee Fan Local Fauna potentially represents the fauna and ecosystem that occupied an unflooded Naarm (Port Phillip) during a Late Pleistocene glacial interval. It can inform palaeoecological reconstructions of faunal dispersal across the newly emergent Bassian land-bridge and illustrate subaerial Naarm’s ecosystem immediately prior to, or coincident with First Peoples’ presence in south-eastern Australia. Avenues for further research on chronology, habitat, climate, and landscape geomorphology are presented. To date, the following taxa are recognised from the site: Palorchestes azael; Palorchestes cf. parvus; Diprotodontidae cf. Diprotodon optatum; Macropus giganteus; M. g. titan; Notamacropus rufogriseus; Protemnodon anak; Protemnodon cf. mamkurra; Procoptodon rapha; Sthenurus andersoni; Sthenurinae cf. Simosthenurus, Vombatus ursinus; Lasiorhinus krefftii; Thylacoleo carnifex; Sarcophilus laniarius and Aves cf. Megapodiidae. Other small to medium (critical weight range) marsupials represented are yet indeterminate to species. bIO
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16.10 - 16.35
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NEW TIME - Dr. Josephine Brown, Atmospheric Science (University of Melbourne)
What past climates can tell us about the future: a modelling perspective AbSTRACT
Climate models can be used to simulate a range of past climates as well as providing projections of future climate. Simulations of past warm climates such as the Pliocene can be compared with reconstructions to evaluate changes in rainfall and atmospheric circulation, providing detailed information about the last time that greenhouse gases were at current levels. We can also use simulations of Holocene and glacial climates to examine changes in regional climate features such as the Australian monsoon in response to altered seasonal and annual average temperatures. Model results from the Australian ACCESS-ESM1.5 model are compared with results from the Paleoclimate Modelling Intercomparison Project to identify common model responses to past changes, including shifts in tropical and subtropical climates over the Australian region. bIO
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16:35 - 18.00
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Drinks and nibbles
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18.00 - 19.00
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Professor Kliti Grice, Geochemistry (Curtin University)
Selwyn Keynote, Public Lecture Role of anaerobic & aerobic microbial communities during severe mass extinctions & in soft tissue preservation AbSTRACT
The largest mass extinction ‘event’ of life (end-Permian) occurred when atmospheric O2 levels were low & CO2& H2S rising under severe hothouse conditions. In contrast to the meteor induced end-Cretaceous extinction event that wiped out non-avian dinosaurs, climate forces of the end-Permian event came from the aggregation of Pangea and its volcanism. Green sulfur bacteria (GSB) were globally plentiful in the Late Permian seas implying abundant H2S, used by GSB in photosynthesis. Similar conditions have been invoked during all past global warming & biotic crises. However, recent molecular data showed conflated global carbon cycle disruptions for the end-Triassic extinction were related to an abrupt drop in relative sea level, and transition from marine to non-marine conditions with an emergence of microbial mats (MMs). The existence of MMs in the ‘extinction zone’ of the Chicxulub asteroid crater show that photosynthesis in the seas recovered within 200 kyrs. Detection of perylene (a fungal wood biomarker) in the crater tracked tsunami which flooded the crater within days after the impact - the first molecular days to week’s resolution of a tsunami. Some exceptionally preserved fossils inside concretions often show soft tissues or articulated skeletal remains. This unique preservation of biomass is likely due to sequestration, and protection from degradation, for tens to hundreds of Ma by a rapid (days) microbial-induced carbonate deposition within days to months. Fossil concretions are a previously untapped biochemical record - providing many unique insights: e.g. diet; role of MMs in fossilisation; and the unique chemical pathways of natural products into biomarkers. During this presentation, examples of different modes of preservation (importance of microbial oxidative-reductive processes) of biomarkers (biomolecules) and soft tissue will be presented with key examples from e.g. Devonian Gogo Formation (Canning Basin), Carboniferous Mazon Creek (Illinois, USA), Cretaceous Winton Formation (Queensland), Eocene Green River Formation (Utah, USA) and Cretaceous Santana Formation (Brazil). bIO
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19.30
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Symposium Dinner
Café Corretto, Lygon St, Carlton (registration required, additional cost) |
Convenors: Dr Anne-Marie Tosolini, Dr Vera Korasidis, Dr Ashleigh Hood
