Slow exhumation of the Greater Himalaya in the Yadong region, the transition between the Central and Eastern Himalaya, during the Late Neogene

Abstract

The Yadong area, at the geographic boundary between the Central and Eastern Himalaya, contains the largest along-strike structural discontinuity in the Himalaya. We conducted zircon fission track (ZFT)and apatite (U–Th)/He (AHe) dating along a 50 km transect of the Greater Himalaya Sequence (GHS) to investigate the cooling and exhumation of this structural discontinuity. New ZFT (14.0–8.2\u2005Ma) and AHe (11.1–4.2\u2005Ma) data suggest fast tectonic exhumation of the GHS in the Middle Miocene. After this pulse of rapid exhumation, the area remained in a long-term slower and steady state of exhumation (c. 0.32\u2005km/Ma since c. 7.7\u2005Ma). New stream topographic analysis also confirms this slow surface erosion in the hinterlands whereas the frontal range underwent enhanced erosion, possibly due to southward upthrusting along the Main Boundary Thrust and Main Frontal Thrust. Our data underline distinctive exhumation patterns between the Eastern and Central Himalaya and suggest that exhumation of the Himalaya was primarily driven by tectonics associated with the underlying Main Himalaya Thrust (MHT). The long-term, slow and steady exhumation in the Yadong area and the Eastern Himalaya hinterland since the Late Neogene is consistent with the gentle dip of the MHT supporting a slab tear of the subducting Indian Plate.