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

古生代末期的极端环境表现为海洋的严重退化、严重的动物和植物灭绝以及地球化学和同位素异常（如Holser和Magaritz, 1987; Erwin, 1993； Veevers等，1994）。由于缺乏可靠的地质年代学数据，寻找一个或多个原因以及确定观测到的现象之间的遗传联系受到阻碍。虽然二叠纪-三叠纪（P-T）界线的年代已经相当清楚，但仍有许多工作要做，以检验界线事件是否在全球等时，并建立界线前后事件的时间尺度。灭绝是持续的还是快速的，或者是脉冲式的，这取决于对时间尺度更好的校准。结合磁地层资料，提供高精度的tephras Ar/Ar和U/Pb测年，将大大提高时间尺度的分辨率。建立一个校准良好的磁极时间尺度将促进全球相关性，并有助于避免因动物地方性和生物地层边界可能的历时性而产生的问题。拟议中的研究将集中在美国西部内陆地区，那里已经获得了许多数据和样本。该项目还将包括地质年代学工作和古地磁可行性研究，这将有助于确定阿根廷、澳大利亚、中国、格陵兰岛、新西兰和南非的剖面是否值得进一步研究，以实现该项目的目标。

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.