COLLABORATIVE RESEARCH: Calibration of Late Cenozoic Incision, Uplift, and Erosion Along the Indus River, Northern Pakistan

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Understanding of the evolution of alpine topography in many mountain chains represents an unresolved problem. A region like the northwestern Himalaya provides a particularly intriguing site for the study of evolving topography, because it is characterized by rapid Quaternary denudation, differential uplift, rivers showing some of the highest gradients and largest sediments loads in the world, a breadth of climatic regimes, active tectonicsm, and extreme topographic relief. In the absence of knowledge of rates of denudation, bedrock uplift, and surface uplift, reconstructions or models of topographic development are forced to rely on untested assumptions concerning the absolute magnitude and relative importance of each of these factors. In the northwestern Himalaya and Karakoram, it appears possible however, to combine digital elevation data sets with chronologic and geomorphic data on timing and magnitude of incision, erosion, and uplift in order to provide a calibrated perspective on topographic evolution of this dynamic region. The goals of this study are to define the timing and rates of incision and bedrock cooling in this part of the Himalayan orogen; to make volumetric approximations of regional denudation, reconstruct base- level changes along this part of the Indus River; and to reconstruct the interactions among tectonically generated localized uplift, regional uplift (tectonic or isostatic), and erosion and denudation. The approaches that will be used include: exposure-age dating of strath surfaces using cosmogenic nuclides; development of cooling ages histories using multi-mineral dating of vertical relief sections; reconstruction of river profiles based on temporal and geometric constraints; and analysis of slopes, altitudinal distributions, gradients, and volumes based on digital elevation data set for the NW Himalaya.