High-resolution geochronology is instrumental in testing proposed causal links between continental-scale, short-term volcanic events and environmental crises. This collaborative research proposal is aimed at unraveling the timing of the end-Guadalupian (ca 260 Ma) mass extinction and its temporal relation to the Emeishan volcanic province in W China. Geochronological research will be complemented with paleo-enviromental studies (delta13C stratigraphy) and biostratigraphy. Currently existing geochronological and paleo-environmental data suggest a causal link but are scarce and insufficient for testing this hypothesis with confidence, because age data constraining the Emeishan volcanism and the extinction event are imprecise and inaccurate (with several Ma uncertainties), and delta13C studies are restricted to short profiles from only a few sites. Therefore, fundamental questions remain unanswered. In addition to testing the hypothesis of a causal link PIs intend to study (1) to what extent the extinction event is diachronous among localities and environments (2) the rate of the biotic recovery in the Late Permian (3) the correlation of extrema in ocean chemistry (if present) with pulses of volcanism and with rates and modes of recovery. In detail, PIs will analyze minerals (zircon, sanidine) from ash-layers within marine and terrestrial sections recording the end-Guadalupian event in China and Australia, applying a zircon pre-treatment which is proven to dramatically improve the quality and reliability of high-resolution TIMS U-Pb zircon data by eliminating the effects of Pb loss. 40Ar/39Ar dating will be employed as a further constraint. In addition to the sedimentary sections they will target Emeishan volcanic products with both U-Pb and 40Ar/39Ar analyses applied to zircon and baddeleyite, and plagioclase, respectively. Through careful integration of U-Pb and 40Ar/39Ar geochronology with chemo- and biostratigraphy, the time scale of the Middle through Late Permian will be greatly improved and will lead to more realistic evaluation of potential causes for the biotic crisis and its aftermath. The research proposed herein is of fundamental importance to understanding first-order processes in Earth History. In particular the understanding of environmental anomalies has become a prime focus of research in Earth Sciences and other areas. PIs will make their findings accessible to a wider audience by collaborating with the University of California Museum of Paleontology and their public outreach program.
