Rivers in the Himalayas: investigating links between tectonics, climate and topography

地球地形的形状反映了构造、气候和沉积物输送过程之间的相互作用。因此，分析和量化景观形态提供了从地形数据中提取构造信息的可能性，如断层运动速率和高地震活动区域。在过去的几十年里，地球仪上可用的高分辨率地形数据数量呈指数级增长，这为我们识别整个地貌和造山带范围内的地貌过程的能力带来了一场革命。喜马拉雅山脉是构造对地形影响的最显著例子之一，几个世纪以来，它一直吸引着地球科学家。许多研究表明，喜马拉雅山脉的地形对活动构造有反应，这一点通过对河流网络的分析（例如Seeber和Gornitz，1983年）和剥露模式的分析（例如King等人，2016年，货车der比克等人，2016）。相比之下，其他工作者认为，气候，通过引起集中侵蚀，可以控制变形和构造过程的模式（例如Finlayson等人，2002年，Thiede等人，2004年）。最近的研究表明，喜马拉雅山的冰川引起的侵蚀可能控制了地形的形状和模糊了构造的特征（亚当斯等人，2020年）。气候、构造和地表过程之间的联系和反馈尚未得到充分了解。探索这些反馈的一个潜在方法是通过检查河流阶地，这是地质时期气候和构造的丰富沉积档案。例如，Lavé和Avouac（2000年）指出，西瓦利克山麓的阶地记录了沿喜马拉雅主锋面逆冲带沿着的活跃褶皱。Sinclair等人（2017）将结构测绘与阶地沉积物的年代测定相结合，测量了喜马拉雅山脉西北部印度河流域的构造缩短，证明了阶地重建构造的潜力。然而，以前的研究受到我们绘制河流阶地并在大空间尺度上量化其几何形状的能力的限制。本项目将探索喜马拉雅山前构造和地形之间的联系。学生将使用新技术从地形自动绘制梯田，以汇编整个喜马拉雅山前的梯田表面，并探索对梯田海拔和几何形状的控制。将利用阶地的分布来限制主要断层在山前的运动，同时将利用阶地沉积学来探索流域规模的过程，如河流流量、滑坡和冰川作用的过去记录。有针对性的实地工作将有助于确定阶地沉积物的特征和地表年代，以验证地形分析的结果。这些数据将与现代的构造观测数据相结合，如国际合成孔径雷达产生的应变率和地震数据集，沿着卫星产生的气候观测数据。

The shape of Earth's topography reflects the interplay between tectonics, climate, and sediment transport processes. Analysing and quantifying landscape morphology therefore provides the potential for extracting tectonic information, such as rates of fault motion and regions of high seismicity, from topographic data alone. In the past few decades, the amount of high-resolution topographic data available throughout the globe has increased exponentially, providing a revolution in our ability to identify geomorphic processes across the scale of whole landscapes and orogens.One of the most striking examples of the impact of tectonics on topography is the Himalayan mountain range, which has fascinated geoscientists for centuries. Many studies have suggested that topography in the Himalayas is responding to active tectonics, shown by analysis of river networks (e.g. Seeber and Gornitz, 1983) and exhumation patterns (e.g. King et al., 2016, van der Beek et al., 2016). In contrast, other workers argue that climate, by causing focused erosion, can instead control the pattern of deformation and tectonic processes (e.g. Finlayson et al., 2002, Thiede et al., 2004). Recent work has suggested that rainfall-induced erosion in the Himalayas may control topographic form and obscure signatures of tectonics (Adams et al., 2020). Links and feedbacks between climate, tectonics and surface processes have yet to be fully understood. One potential way to explore these feedbacks is through the examination of fluvial terraces, a rich sedimentary archive of climate and tectonics through geological time. For example, Lavé and Avouac (2000) showed that terraces in the Siwalik foothills recorded active folding along the Himalayan Main Frontal thrust. Sinclair et al. (2017) combined structural mapping with dating of terrace sediments to measure tectonic shortening across the Indus River Valley in the NW Himalayas, demonstrating the potential that terraces hold for reconstructing tectonics. However, previous studies have been limited by our ability to map fluvial terraces and quantify their geometry over large spatial scales.This project will explore the links between tectonics and topography across the Himalayan mountain front. The student will use new techniques for mapping terraces automatically from topography to conduct a compilation of terrace surfaces across the entire Himalayan mountain front and explore controls on terrace elevations and geometry. The distribution of terraces will be used to constrain the motion of major faults across the mountain front, while terrace sedimentology will be used to explore catchment-scale processes such as the past records of fluvial discharge, landsliding and glaciation. Targeted field work will allow the characterisation of terrace deposits and surface dating, to validate the results of the topographic analysis. These data will be integrated with modern observations of tectonics such as InSAR-derived strain rates and seismic datasets, along with satellite-derived climate observations.