Correlation, Dating, and Geologic Significance of Late Teriary Tephra-Rich Strata in the Basin and Range Province

晚第三纪，在美国西部盆地和山脉省广泛分布的富含泥页岩的沉积地层明显比更古老的丰富。第三系沉积地层，并在全省形成的断界伸展盆地中聚集。为了更好地了解这些富铅矿地层及其伴生盆地的性质和区域意义，需要更好地控制它们的年龄和地理分布。为此，pi将在盆地和山脉北部这些稀疏化石的晚第三纪地层中建立硅质层序，并将对选定的样品进行定年。将使用玻璃相的痕量/微量元素化学，以及玻璃颗粒的大小和形状分析来表征tephra。为了确定地层的年代，pi将使用40Ar/39Ar激光聚变技术对白晶石和黑云母进行测定，这是白晶石中常见的斑晶。研究结果还将有助于了解该地区晚第三纪硅酸火山活动的时间、频率和强度，并为今后这些地层的构造、地层学和古生物学研究提供基本的参考框架。

Late Tertiary, tephra-rich sedimentary strata widespread in the Basin and Range Province of the Western United States are markedly more abundant than older. Tertiary sedimentary strata, and have accumulated in fault- bounded extensional basins formed province-wide. As a step towards better understanding the nature and regional significance of these tephra-rich strata and their associated basin, better control is needed on their age and geographical distribution. Towards this end PIs will establish the sequence of silicic tephra layers in these sparsely fossiliferous Late Tertiary strata in the northern Basin and Range, and will date selected samples. The tephra will be characterized using trace/minor element chemistry of the glass phase, and size, and shape analysis of the glass particles. For dating the layers PIs will use the 40Ar/39Ar laser fusion technique on sanidine and biotite, common phenocrysts in the tephra. The results will also add to the understanding of time, frequency, and magnitude of silicic volcanism in the Late Tertiary of the region, and the tephrochronology will provide a fundamental reference framework for future structural, stratigraphic, and paleontologic studies of these strata.