Collaborative Research: The Permian-Triassic Transition in Antarctica: Evaluating the Rates and Variability of Carbon Isotope Fluctuations in Terrestrial Organic Matter

This investigation will examine proposed hypotheses for the cause(s) of the Permian- Triassic extinction, which is generally recognized as the largest biotic extinction of the past 550 million years. The proposed mechanisms for the Permian-Triassic climatic deterioration and its aftermath are predicted to act over a characteristic timescale and leave a unique ordering of global-scale markers in marine and terrestrial records. The PI's will examine the relative timing and duration of changes in terrestrial carbon cycling associated with extinctions in relatively thick and expanded Permian-Triassic successions of the Cumulus Hills region in the central Transantarctic Mountains of Antarctica. Our study of the Permian-Triassic Buckley and Fremouw formations in the Cumulus Hills will contribute uniquely to the debate by generating high-resolution 8l3C records of terrestrial organic matter that have been separated using densitygradient centrifugation. This will ensure that observed 013Cexcursions are compared using the same plant components and address the relative importance of primary changes in the oceanatmosphere system versus differences in organic matter preservation in a changing terrestrial ecosystem. Collection of zircons from multiple ash beds that have been found in these fluvial sequences will be used for high-precision U/Pb dating with Isotope Dilution Thermal Ionization Mass Spectrometry (ID-TIlMS) in collaboration with Dr. Sam Bowring at the Massachusetts Institute of Technology. By placing geochronometric constraints on the timing and duration of terrestrial 813Cexcursions and changes in carbon cycling that occur not only at the Permian- Triassic boundary but well into the early Triassic, the proposed research will examine the long term coupling of the marine and terrestrial carbon cycles via the atmosphere and riverine input. Broader Impacts: The proposed resE:archwill support graduate and undergraduate student theses at Ohio State University and the University of Kentucky, including those from underrepresented groups. Students will receive broad training in field and laboratory settings using a variety of geochemical and stratigraphic techniques. The researchers will also be involved in outreach activities beyond the standard dissemination of scientific information at meetings and in peer review publications. Secondary-school students will be involved through efforts to bring the Antarctic field experienc:e related to the study of the Permian-Triassic mass extinction to the classroom. The geochemical and sedimentologic database assembled will provide a key reference section for the Permian-Triassic boundary in high latitudes of Gondwana. It will promote a better understanding of carbon cycling on geological timescales and its relationship with past climates and ecosystems which will provide an important societal perspective in the context of the magnitude and impact of human-induced climate change.