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

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.