Large-scale topography of the north Tibetan ranges as a proxy for contrasted crustal-scale deformation modes

Forming the northern margin of the Cenozoic Himalayan-Tibetan orogen, the area surrounding the Qaidam Basin is a key region to study the mechanisms that govern the long-term evolution of intracontinental orogenic processes. Indeed, tectonic deformation in this region involves newly formed and inherited crustal and lithospheric structures, partition between horizontal and vertical movements, and a strong influence from external factors such as climate and erosion. This study proposes a description of the topography and crustal structure of the north Tibet ranges as an insight into their tectonic deformation characteristics. The topographic study includes the integrated analysis of regional topographic profiles, river profiles, slope maps and thermochronology data. The available geophysical, geological and structural data are used to draw regional, crustal-scale geological sections across northern Tibet to describe the regional crustal structure. We show that three deformation modes are expressed (block uplift, distributed shortening and crustal buckling) in structural compartments that involve either complete mountain ranges or some specific regions inside those ranges. We propose that anew crustal structure may develop parallel to the Altyn Tagh fault, connecting the eastern tip of the Qimen Tagh with the Haiyuan fault, across the Qaidam Basin.