Tectonic Processes in Upper Crustal Normal Fault Systems

南维珍山脉，内华达州，占据了高度延伸的米德湖地区的最东端。我们请求资金用于完成内华达州南维珍山脉的详细地质测绘和地质年代学研究。就暴露程度、地层分辨率、地形起伏度和重建的区域基准而言，南维尔京山脉是世界上上地壳叠瓦状正断层构造的最佳范例之一。迄今为止，由PI和研究生Robert Brady绘制的地图表明，多米诺骨牌式、“滚动铰链”和滚动运动学都可能在系统中活跃，但可能在不同的时间和地点在裂谷走向中起作用。因此，该地区提供了测试这些模型适用性的潜力，并可能确定一系列倾斜区块内的结构位置如何影响其发展。除了地质填图外，我们建议完成选定样品的Ar/Ar和U-Th/He定年，分别确定盆地形成和块体拆顶的绝对年龄。后一种方法在磷灰石矿物中具有独特的低闭合温度，约为70℃，该项目将是He定年法首次应用于伸展构造问题。

9628262 Wernicke The South Virgin Mountains, Nevada, occupy the easternmost portion of the highly extended Lake Mead region. We request funds for completion of detailed geologic mapping and geochronologic studies in the South Virgin Mountains Nevada. In terms of exposure, stratigraphic resolution, topographic relief and a regional datum for reconstruction, the South Virgin Mountains are among the best examples of upper crustal imbricate normal fault structure in the world. Mapping to date by the PI and graduate student Robert Brady suggests that domino-style, "rolling-hinge," and rollover kinematics are all probably active within the system, but may be operative at different times and places across strike of the rift. Hence the area offers the potential to test the applicability of these models, and possibly determine how structural position within a series of tilted blocks influences their development. In addition to geologic mapping, we propose to complete Ar/Ar and U-Th/He dating of selected samples to establish absolute ages of basin formation and unroofing of the blocks, respectively. In the case of the latter method, which has a uniquely low closure temperature of about 70oC in the mineral apatite, this project will be the first application of He dating to the problem of extensional tectonics.