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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9614324 Renne Environmental crises at the end of the Paleozoic are indicated by evidence for profound marine regression, severe faunal and floral extinctions, and geochemical and isotopic anomalies. 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 an U/Pb dates for sanidine and zircon from tephras combined with magnetostratigraphic data, which would vastly improve the resolution of the time scale. Establishing a well-calibrated magnetic polarity time scale for the "Illawara" reversals after the Kiaman Superchron will facilitate global correlations and help obviate problems arising from faunal provincialism and possible diachronism of biostratigraphic boundaries. The proposed research would concentrate on accessible, well-studied sections in the western U.S. (Texas, New Mexico, and Wyoming) for which many samples and some data have already been obtained. Additional feasibility studies are proposed, at little or no cost to this project, which would help determine whether sections in Antarctica, Argentina, China, and South Africa merit future research towards the goals of this project.