LELAND STANFORD JUNIOR UNIVERSITY, THE

High-resolution geochronology is instrumental in providing evidence for a causal link between continental-scale, short-term volcanic events and environmental crises. We seek support for a three year collaborative research proposal aimed at unraveling the timing of the end-Guadalupian (ca 260 Ma) mass extinction and its temporal relation to the Emeishan volcanic province inW China. Geochronological research will be complemented with paleo-enviromental studies (?13C 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 ?13C 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 we intend to study (1) to what extent the extinction event is diachronous among localities, and how precisely it can be correlated by geochronologic, chemo- and biostratigraphic techniques (2) the temporal relation between terrestrial and marine records of the event (3) the rate of the biotic recovery in the Late Permian (4) the extent to which the end-Guadalupian and end-Permian extinctions are related in terms of causality, and (5) the correlation of extrema in ocean chemistry (if present) with pulses of volcanism and with rates and modes of recovery. In detail, we propose analyzing minerals (zircon, sanidine, biotite) from ash-layers within marine and terrestrial sections recording the end-Guadalupian event inChinaandAustralia, 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 we will target Emeishan volcanic products with both U-Pb and 40Ar/39Ar analyses applied to zircon (and baddelyite) 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. 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. Reliable, high-resolution radio-isotopic ages are of prime importance for the understanding of short-term processes and events in Earth's history, such as climate change, rapid biotic evolution, and globally catastrophic occurrences, as shown by the present demand by the Earth Science community in general for improvement in both quantity (in the sense of ease-of-access to) and quality of dating. Complementary and carefully integrated studies of paleo-environmental proxies and fossil records have the potential to provide a robust basis for a hypothesis about causes for biotic crises and the reconstruction of their aftermath. Our findings will be propagated into educational curricula through courses taught at UC Berkeley (by the PIs Renne and Mundil) and Stanford University (by PI Payne) and disseminated through publications and symposia. All aspects of the project will involve postdoctoral and graduate researchers from Berkeley and Stanford, enhancing their training as research scientists by collaborating in a team with specialists from different fields.

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