Late Cenozoic Foreland‐to‐Hinterland Low‐Temperature Exhumation History of the Kashmir Himalaya

Abstract

AbstractNew apatite and zircon (U‐Th)/He cooling ages quantify late Cenozoic exhumation patterns associated with fault activity across the Kashmir Himalaya. Apatite (U‐Th)/He (AHe) cooling ages of detrital grains from the Sub‐Himalayan foreland sediments indicate significant resetting. AHe data and thermal modeling reveal cooling and exhumation initiated by 4 Ma at the deformation front and by 2–4 Ma throughout other Sub‐Himalayan structures. Exhumation rates for Sub‐Himalayan structures are ≥1 mm/year. In the hinterland, thrust sheet samples from the Main Boundary thrust and Main Central thrust yield AHe cooling ages between 5.1 and 21.1 Ma. Published apatite fission track cooling ages (<3 Ma) and high exhumation rates (3.6–3.2 mm/year) across the Kishtwar window further to the north are consistent with AHe data from the Sub‐Himalayan structures. The pattern of cooling ages and rates indicates that exhumation occurs in association with changes in the Himalayan basal décollement ramp geometry. Hinterland zircon (U‐Th)/He (ZHe) data show a pronounced abundance and probability spike in cooling ages between 14 and 21 Ma, a period when Main Central thrust motion is well documented throughout the Himalaya. ZHe single‐grain ages from Sub‐Himalayan samples contain a nearly identical cluster from 16 to 23 Ma. Cooling patterns across the Kashmir Himalayas do not correlate spatially with modern monsoon precipitation, suggesting that climate‐related precipitation and exhumation are decoupled. Coeval translation over the basal décollement and distributed imbricate thrust deformation of the foreland in the upper plate characterizes fault‐related exhumation of the Sub‐Himalayan orogenic belt after 4 Ma.