Quantifying Long-Term Variations in tectonic and Climate-Driven Exhumation: Northwest Himalaya, India

构造与气候侵蚀的相互作用和耦合是活动造山带长期演化的一级控制，并提出了解释造山带构造演化中由构造控制的折返过程向侵蚀控制的折返过程转变的概念。气候驱动的侵蚀在多大程度上控制了喜马拉雅南部前缘上新世/第四纪的发展，这是一个有争议的问题。喜马拉雅山脉形成了一个坡度很大的地形屏障。因此，量化气候、降水、侵蚀和变形模式随地质时间的变化是否相关，将为造山带的演化提供重要的见解。我们建议整合多个低温热计时仪和热运动学模型，以检验围绕喜马拉雅前缘气候、构造和侵蚀相互作用的两个有争议的假说：(1)我们将测试从约10 Ma到现在，南喜马拉雅前锋的折返是否从构造机制转变为气候控制机制，以及(2)现代降水和侵蚀速率之间的空间相关性是否在百万年时间尺度上持续存在。为了验证这些假设，我们将处理30个新的40Ar/39Ar白云母、锆石(U-Th)/He(Ze)和磷灰石裂变径迹(AFT)冷却年龄。数据集将延伸到一段约100公里宽的路段，与喜马拉雅锋面平行的强降水梯度。新的温度计时数据将限制侵蚀的空间和时间变化，以及几个主要结构上变形时间和幅度的走向变化。我们将把这些数据与3D热运动学模型相结合，以模拟西北喜马拉雅前缘的热、结构和侵蚀演化。将针对不同的侵蚀和断层历史对三个终端成员进行测试。

Interactions and coupling between tectonics and climate-driven erosion are a first order control on the long-term evolution of active orogens and concepts have been developed that explain the changeover from tectonically to erosionally controlled exhumation processes in the tectonic evolution of orogens. The degree to which climate-driven erosion controls the Pliocene/Quaternary development of the southern Himalayan front is a matter of debate. The Himalaya forms an orographic barrier with strong gradients. Thus quantifying weather or not precipitation, erosion, and deformation patterns are correlated over geologic time should provide important insights into evolution of the orogen. We propose an integration of multiple low-temperature thermochronometers and thermokinematic models to test two controversial hypotheses surrounding the interaction of climate, tectonics, and erosion across the Himalayan front: (1) We will test if exhumation of the southern Himalayan front switched from a tectonic to climate-controlled mechanism between ~10 Ma and present, and (2) if spatial correlations between present-day precipitation and erosion rates have been persistent over million year timescales. To test these hypotheses we will process thirty new 40Ar/39Ar muscovite, zircon (U-Th)/He (ZHe), and apatite fission track (AFT) cooling ages. The data sets will extend over a ~100-km-wide segment with strong precipitation gradients parallel to the Himalayan front. New thermochronometer data will constrain spatial and temporal variations in erosion and along strike variations in the timing and magnitude of deformation on several major structures. We will integrate the data with a 3D thermokinematic model to simulate the thermal, structural, and erosional evolution of the NW Himalayan front. Three end-member scenarios will be tested for different erosion and faulting histories.