Collaborative Research: Investigating Early Triassic Ocean Chemistry, Stratigraphy, and Paleobiology During the Protracted Biotic Recovery from the Permo-Triassic Mass Extinction

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ABSTRACTThe most devastating mass extinction since the origin of animals occurred at the end of the Permian Period (c. 251 million years ago) when over 80% of all marine species went extinct. The marine realm remained perturbed into the subsequent Triassic Period for several million years after the extinction events, but the details are poorly known and may help us more completely understand the extinction. Unusual geologic features reminiscent of earlier times in Earth's history, such as seafloor precipitated aragonite fans, subtidal stromatolites, and remarkable excursions in seawater d13C and d34S, indicate that atypical ocean chemistries and environments persisted into the Early Triassic, but their exact nature is not well-understood, given the boundary-centric nature of previous studies. We will investigate connections between unusual biotas, anachronistic lithofacies, strong isotopic shifts (d13C, d34S) and the protracted animal recovery in the Early Triassic (the geologic period following the mass extinctions). The western U.S., our proposed study area, resided on the eastern margin of the giant Panthalassic Ocean during this geologic time and thus provides a global comparison with ongoing research elsewhere (China, Europe, etc.). Our preliminary 87Sr/86Sr work in the western US demonstrates that samples are well preserved and that 87Sr/86Sr provides sub-stage time correlation potential. Sulfur-rich deposits that reflect seawater conditions are rare in the rock record. We will surmount this problem by using a new technique to extract sulfur isotopic information from normal marine limestones (the so-called "carbonate associated sulfate" or CAS), which are common around the world. The assembled dataset will likely be the first of its kind and reveal features that may give insight into the mass extinction not previously recognized.