Active Tectonics and Erosional Unloading at the Eastern Margin of the Tibetan Plateau

The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography, coupled with abundant Mesozoic thrusts within the margin, explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually, it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere; the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening.