PhD: Empty waters? Explaining the absence of Ediacaran macro-organisms in shallow-marine Avalonian palaeoenvironments

Brief summary:
Use sedimentology and facies characterization to explain why certain late Ediacaran palaeoenvironments in the UK and Newfoundland are seemingly devoid of early animal fossils.

Importance of the area of research concerned:
Earth’s oldest animal fossils are found in the late Ediacaran Period, 574–539 million years ago. Global compilations of species occurrence reveal a substantial latest Ediacaran decline in fossil diversity. This pattern has been obtained almost entirely from coarse-grained siliciclastic, shallow marine sedimentary facies, and is increasingly interpreted as evidence for Earth’s first mass extinction event. However, a contemporaneously deposited suite of Ediacaran localities in Canada, Norway and the U.K. bearing fine-grained siliciclastics exhibit markedly different fossil assemblages, and a depauperate biota across the supposed ‘extinction’ interval. Without detailed characterization of these neglected depositional environments, assured evidence for a global mass extinction cannot be categorially refuted, with alternative preservational, ecological or environmental explanations for the latest Ediacaran fall in biodiversity remaining possible.

Project summary :
This project will characterize the sedimentology, petrology and palaeobiology of Ediacaran shallow marine sedimentary successions of Newfoundland (Canada) and Shropshire (U.K.) to characterise their depositional environments, and to determine the link between specific facies and fossil taxa. Past research in these regions has largely neglected detailed sedimentological study. Facies characterization and regional correlation will permit reconstruction of depositional environments. Findings will be measured against directly comparable datasets from other global localities of similar bathymetry and environmental setting, namely the Ediacara Member (South Australia), Vendian successions of the White Sea region (Russia), and Nama Group (Namibia), to investigate the causes of variation in fossil densities, and sedimentary facies, within these globally significant localities.

What will the student do?:
You will produce detailed sedimentological logs through key sections through the Musgravetown, St. John’s and Signal Hill Groups (Avalon and Bonavista peninsulas, Newfoundland), and the Longmyndian Supergroup (U.K.), documenting fossil occurrence within individual facies. Petrological study will investigate micro-scale variation in sedimentological structures, permitting refinement of environmental interpretation and sediment sources. Your data will yield robust interpretations of depositional environments for these regions, and will contribute towards a broader effort within our research group to establish the true environmental influence on fossil distribution and preservation in Ediacaran shallow marine settings.

References:
McMahon, W.J., Liu, A.G., Tindal, B.H. and Kleinhans, M.G. 2020. Ediacaran life close to land: coastal and shoreface habitats of the Ediacaran macrobiota in the central and southern Flinders Ranges, South Australia. Journal of Sedimentary Research (In Press)
Darroch, S.A., Smith, E.F., Laflamme, M., & Erwin, D.H. 2018. Ediacaran extinction and Cambrian explosion. Trends in Ecology & Evolution, vol. 33, pp. 653-663.
Normore, L.S. 2011. Preliminary findings on the geology of the Trinity map area (NTS 2C/06), Newfoundland. Current Research: Newfoundland and Labrador Department of Natural Resources, Geological Survey Report, vol. 11, p. 1.