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

9614324古生代末期雷恩环境危机的证据表明，严重的海洋退化、严重的动植物灭绝以及地球化学和同位素异常。寻找一个或多个原因，以及在观察到的现象之间建立遗传联系，由于缺乏可靠的地质年代学数据而受到阻碍。尽管二叠系-三叠系(P-T)界线现在已经确定了合理的年代，但仍有许多工作要做，以检验边界事件是否在全球范围内同步，并建立边界前后事件的时间尺度。无论灭绝是持久的、迅速的，还是以脉冲形式发生的，都取决于对时间尺度的更好校准。本文提出的研究将结合磁性地层学数据为闪锌矿和锆石提供高精度的Ar/Ar和U/Pb年龄，这将大大提高时间尺度的分辨率。为Kiaman Superchron之后的“Illawara”反转建立一个校准良好的磁极时标，将促进全球对比，并有助于避免因动物群地方性和生物地层界线可能的历时性而产生的问题。拟议的研究将集中在美国西部(德克萨斯州、新墨西哥州和怀俄明州)可访问的、经过充分研究的部分，这些地区已经获得了许多样本和一些数据。建议进行更多的可行性研究，对该项目的成本很低或没有成本，这将有助于确定南极洲、阿根廷、中国和南非的路段是否值得进一步研究，以实现该项目的目标。

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.