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

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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.