Insights into topographic evolution and the timings of deformation phases in large mountain ranges

Geological studies show that the onset of E-W extension in southern Tibet significantly post-dates the onset of the India-Asia collision. I will present dynamic models of the evolution of large mountain ranges that provide insights into the timings of deformation episodes. The gravitationally-driven flow of mountain ranges over rigid underthrusting plates (e.g. southern Tibet over the Indian lithosphere) results in the formation of mountain ranges with curved margins. As curvature on range margins develops, so does the importance of arc-parallel extensional stresses within the range interior. The models show that for viscosities that are consistent with previous independent estimates, the curved southern margin of the Tibetan Plateau could form within the timespan of the India-Asia collision. Additionally, the time delay between collision and the onset of normal-faulting in southern Tibet is consistent with the time taken for the topographic curve, and the resulting extensional stresses, to develop.