Collaborative Research: Calibrating the end-Ediacaran Extinction with U-Pb Geochronology & Chemostratigraphy at a New Precambrian-Cambrian Boundary Site in Namibia & South

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The first appearance and rapid diversification of complex, multicellular animals at the dawn of the Cambrian (~540 million years ago) is conceivably the single most significant episode in the evolution of life on Earth, as it laid out the initial blueprints for the vast majority of life forms that exist today. Understanding the driving mechanisms of the Cambrian 'explosion' have been challenging because life forms that dominated the preceding period, the Ediacaran, have a sparse fossil record. In addition, the marine sedimentary rocks that preserve the Ediacaran-Cambrian transition are now scattered across the continents, hampering an unequivocal reconstruction of life and the environment at this crucial junction of the geologic history. This study focuses on key outcrops of the Ediacaran-Cambrian marine deposits with spectacular fossils and high potential for precise isotopic dating in a previously unexplored region near the Namibia-South Africa border. The results will provide new insights into the rates of paleoenvironmental and ocean chemical change during this critical time interval. In addition to public presentations and scholarly publications, a comprehensive program of educational, training, and outreach activities are planned.This project employs an integrated program of field mapping, sedimentology, chemo- and bio-stratigraphy on newly discovered marine carbonate-rich and fossiliferous Ediacaran-Cambrian sections on either side of the Orange River in Namibia and South Africa with abundant intercalated ash beds suitable to U-Pb geochronology. It will provide a high-resolution record that will help to unravel the mode and rates of biotic and coeval environmental changes at the close of the Proterozoic. The results will be a major step forward in testing the hypothesis that there were globally synchronous environmental perturbations that were genetically associated with biotic turnover across the Ediacaran-Cambrian boundary, and will lead to a better understanding of the driving mechanisms of the Cambrian radiation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.