Topographic Evolution of the Sierra Nevada - A Stable Isotope Approach

0001208张伯伦在造山过程中，大量构造驱动的岩石隆起与侵蚀过程相结合，产生了高地形。对于造山作用的许多动力学模型来说，对隆升时间的了解是至关重要的，但古地形历史很难确定。该项目将试图利用已知火山年龄和成因的蒙皂石的氧同位素数据，开发内华达山脉的古地形记录。该方法假定蒙皂石在成岩作用时与雨水的同位素组成在成岩作用时迅速、就地、与雨水的同位素组成相平衡，此后没有改变，并且所测得的同位素比值忠实地代表了山区地形的雨影效应，因为天气模式垂直于山脉，从而为所需的古地形提供了一个稳健的雨影效应替代品。一个成功的结果将为科迪勒构造模型提供急需的数据，并将有助于提供和测试这种方法在其他古代造山带中的使用。

0001208ChamberlainDuring orogenesis large amounts of tectonically driven rock uplift combined with erosional processes produces high topography. Knowledge of the timing of uplift is critical to many dynamic models of orogenesis, but paleotopographic history is difficult to determine. This project will attempt to develop a paleotopographic record for the Sierra Nevada by using oxygen isotopic data from smectite of known volcanic age and origin. The method assumes that the smectite developed from volcanic ash quickly, in situ, in equilibrium with the isotopic composition of rain water at the time of diagenesis, unaltered since, and that the measured isotopic ratios faithfully proxy the rain shadow effect of mountainous topography as weather patterns cross mountain ranges orthogonally thus providing a robust rain shadow effect proxy for the desired paleotopography. A successful outcome will provide critically needed data for cordilleran tectonic models, and will help provide and test this method for use in ancient orogens elsewhere.