Collaborative Research: Refinement of the Late Permian and Early Triassic Time Scale through Integrated Ar/Ar and U/Pb Radioisotopic Dating and Magnetostratigraphy

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9614512 Steiner Environmental extrema at the end of the Paleozoic are manifest in evidence for profound marine regression, severe faunal and floral extinctions, and geochemical and isotopic anomalies (e.g. Holser and Magaritz, 1987; Erwin, 1993; Veevers et al., 1994). The search for a cause or causes, as well as establishing genetic links between the observed phenomena, is hindered by a paucity of reliable geochronologic data. Though the Permian-Triassic (P-T) boundary is now reasonably well dated, much work remains to test whether the boundary events were globally isochronous and to establish the time scale of events before and after the boundary. Whether the extinctions were protracted or rapid, or occurred in pulses, relies on better calibration of the time scale. The research proposed herein would provide high-precision Ar/Ar and U/Pb dates for tephras combined with magnetostratigraphic data, which would vastly improve the resolution of the time scale. Establishing a well-calibrated magnetic polarity time scale will facilitate global correlations and help obviate problems arising from faunal provincialism and possible diachronism of biostratigraphic boundaries. The proposed research would concentrate on sections in the western interior U.S. for which many data and samples already been obtained. The project will also include geochronologic work and paleomagnetic feasibility studies are proposed which would help determine whether sections in Argentina, Australia, China, Greenland, New Zealand, and South Africa merit future research towards the goals of this project.