When Life Got Big - Ediacaran evolution in a period of profound global change

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The Neoproterozoic was a time of massive changes in the Earth System that included breakup of supercontinent Rodinia, several 'snowball Earth' ice ages of global extent, marked fluctuations in the isotopic composition of seawater, and increased but fluctuating levels of oxygen in the oceans and atmosphere. Against this backdrop of Neoproterozoic global change we see an equally profound change in the evolution of life, the late Ediacaran (571 million years ago) appearance of abundant specimens and multiple taxa of large and architecturally complex life-forms after three billion years of mostly microbial evolution. The Ediacara biota is a global assemblage of soft-bodied marine creatures, now preserved as fossil impressions under event beds of sandstone or volcanic ash, that underlie the abundant shelly fossils and complex burrows of the Cambrian. Ediacaran life was a mixture of biotic groups that did not survive the end of the Ediacaran Period (e.g. rangeomorphs), alongside stem-group animals that diversified during the Cambrian explosion and were the ancestors of all animal life in our modern world. The oldest Ediacara-type fossil impressions known anywhere are rangeomorph fossils up to 2 meters long that occur in the upper part of the Drook Formation within the newly inscribed Mistaken Point UNESCO World Heritage Site; broadly coeval Avalonian assemblages also occur in central England and NW Canada. Over the next five years, I will assess the inter-relationship between Ediacaran global change and biotic evolution through studies of the oldest Ediacara-type fossils in Avalonian Newfoundland, NW Canada, and Australia and a synthesis extending through the entire period worldwide. Our field studies are stratigraphic, sedimentological, and paleontological and will also utilize international collaborators in isotope and redox geochemistry. In Newfoundland we will analyse a superbly exposed succession of Mall Bay-Drook strata, previously known only at a reconnaissance level, that predate most of the fossiliferous succession at Mistaken Point and thus can provide information on environmental conditions that immediately preceded the appearance of biological complexity in Avalonian Newfoundland. Work in NW Canada will focus on fossils in the deep-water Nadaleen Formation to enhance the data set and interpretation of this recent extension of the Avalonian assemblage into Laurentia. All known occurrences of the Avalon assemblage are from deep-water settings. Our study of the Wonoka Formation, which contains sparse specimens of the oldest Ediacara-type fossils in Australia that may be coeval with the youngest fossils at Mistaken Point, will document the fossils and environmental conditions of these shallower-water carbonate environments. Collectively, these studies will elucidate the early development of large size and biological complexity in the context of Ediacaran global change and will provide training for 2 PhD, 3 MSc and 5 BSc HQP.