Tectonic Control Over Shallow Crustal Exhumation Across the India‐Asia Convergent Margin

Abstract

AbstractUnderstanding the processes and mechanisms responsible for exhumation are essential for determining the evolution of landscapes. Our knowledge of these issues in continental convergent margins is still incomplete despite decades of research. Here, we present a record of exhumation rates obtained from thermochronology across the collision zone of the Himalayan‐Tibetan orogen, which has been carved by the dextral Karakoram fault (KF) along its western margin. Our thermochronology results across the KF suggest that transpression controlled exhumation from ∼10 to 8 Ma. Exhumation rates at the margin of the Tibetan plateau, in the SE Karakoram range, to the north of the KF are twice as high as the Ladakh range, to the south of the KF, since at least middle Miocene. We hypothesize that rapid exhumation of the Tibetan margin was in response to topographic uplift and subsequent erosion due to the convective removal of the lower lithosphere, triggered by the rollback of the subducting Indian lower crust during the Oligocene‐Miocene in an early phase. Our thermochronology results document an additional two‐fold increase in the exhumation rates of the Tibetan margin since the late Mio‐Pliocene. We propose that the underthrusting of the Indian Plate below Tibet during the late Mio‐Pliocene was responsible for this additional increase of exhumation rates of the Tibetan margin in the late phase. These exhumation rates are in good agreement with the topographic slope, relief, and channel steepness data of these regions. Thus, the coupling of tectonics and topography dictated the exhumation patterns since late Mio‐Pliocene.