The Pamir Frontal Thrust System: Rates, Style, and Controls on Deformation

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This project focuses on the structural corridor that lies at the interface between the Pamirs and the Tian Shan in westernmost China. These two, oppositely facing orogens are progressively impinging on each other, and between them, have trapped the largest river in the region, the Kezilesu. Across a spatially compact zone, a diverse array of structures and contrasting deformation mechanisms accommodate rapid convergence, including low-angle thrust faults, reverse faults, fold scarps, folds, and flexural slip faults. Representing the leading edge of the Pamir orogenic wedge, the Pamir Frontal Thrust system is in places immediately adjacent to the Kezilesu River and at others the primary fault lies many kilometers from the river. This along-strike variability provides an opportunity to assess the concept that efficient fluvial erosion can focus deformation. Faster deformation rates farther from the axial river would tend to negate the erosion-deformation hypothesis. Accelerated rates on structures across the southern margin of the Tian Shan that are proximal to the Kezilesu compared to more distal sites would support the erosion-deformation hypothesis. To determine deformation rates, the research team will: delineate regional patterns of deformation at decadal time scales using InSAR; date active surface-rupturing faults using optically stimulated luminescence methods; date deformation of terraces and fans using optically stimulated luminescence, cosmogenic radionuclide, and radiocarbon methods; determine long term slip-rates using magnetostratigraphy and (U-Th)/He dates; and use seismic sections to constrain subsurface structure.The role of active erosion in modulating deformation is still actively debated Whereas the conceptually attractive idea that focused erosion promotes localized and accelerated deformation is predicted by many numerical models very few unequivocal case studies exist that demonstrate such a linkage. This study in the Pamir-Tian Shan may provide unequivocal field evidence for a linkage between erosion and deformation because the region has many favorable attributes that should permit a clear assessment of the pattern and rate of deformation with respect to the river system. In addition to providing insight on the dynamics of mountain belts and assessing a popular tectonic geomorphology paradigm, paleoseismic analysis of several large active faults will improve understanding of the seismic hazards posed by these faults, some of which have produced deadly, recent earthquakes. Finally, the project will involve substantial collaboration with Chinese scientists, research opportunities for graduate and undergraduate students, and outreach to schools and museums.