Topographic Evolution of the Sierra Nevada - A Stable Isotope Approach

[00:20 . 08]张伯伦在造山运动期间，大量的构造驱动的岩石隆起与侵蚀作用相结合，形成了高地形。对于许多造山动力学模型来说，隆升时间的知识是至关重要的，但古地形史很难确定。该项目将尝试利用已知火山时代和起源的蒙脱石的氧同位素数据，开发内华达山脉的古地形记录。该方法假设蒙脱石从火山灰中迅速就地形成，与成岩时期雨水的同位素组成保持平衡，此后未发生变化，并且测量的同位素比率忠实地代表了山地地形的雨影效应，因为天气模式垂直穿过山脉，从而为所需的古地形提供了强有力的雨影效应代表。一个成功的结果将为科迪勒拉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，以便在其他地方的古代造山带中使用。

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.