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

地球地形的形状反映了构造、气候和沉积物运输过程之间的相互作用。因此，分析和量化景观形态提供了仅从地形数据提取构造信息的可能性，例如断层运动速率和高地震活动性区域。在过去的几十年里，全球范围内可用的高分辨率地形数据的数量呈指数级增长，为我们在整个景观和造山带范围内识别地貌过程的能力提供了一场革命。喜马拉雅山脉是构造对地形影响最显著的例子之一，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正在响应活动构造，这可以通过对河流网络的分析（例如Seeber和Gornitz， 1983）和挖掘模式（例如King等人，2016年，van der Beek等人，2016年）来证明。相反，其他研究者认为，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，喜马拉雅地区降雨引起的侵蚀可能控制地形形态并模糊构造特征（Adams et al., 2020）。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对河流阶地的研究，这是一个丰富的地质时期气候和构造的沉积档案。例如，lav<s:1>和Avouac（2000）表明，Siwalik山麓的阶地沿着喜马拉雅主前缘逆冲记录了活跃的褶皱。Sinclair等人（2017）将构造制图与阶地沉积物定年相结合，测量了喜马拉雅西北部印度河流域的构造缩短，证明了阶地在重建构造方面的潜力。然而，以前的研究受到我们在大空间尺度上绘制河流阶地和量化其几何形状的能力的限制。这个项目将探索喜马拉雅山前构造和地形之间的联系。该学生将使用新技术从地形自动绘制梯田，对整个喜马拉雅山前的梯田表面进行汇编，并探索对梯田高度和几何形状的控制。阶地的分布将被用来约束主要断层在山前的运动，而阶地沉积学将被用来探索流域尺度的过程，如河流流量、滑坡和冰川作用的过去记录。有针对性的野外工作将使阶地沉积物的特征和表面测年成为可能，以验证地形分析的结果。这些数据将与现代构造观测相结合，如insar衍生的应变率和地震数据集，以及卫星衍生的气候观测。

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.