LATE CENOZOIC – RECENT EXHUMATION HISTORY OF THE KASHMIR HIMALAYA FROM THE SIWALIK-MURREE BELT TO THE HIGH HIMALAYA USING (U-TH/HE) THERMOCHRONOMETRY

Apatite and zircon (U‐Th)/He cooling ages are used to quantify the recent exhumation pattern associated with fault activity across the Kashmir Himalaya. Here we present thermochronological data from 30 samples, totaling of 74 individual single-grain apatite and zircon (U-Th)/He dated aliquots. Cooling age data were collected from (1) molasse deformed foreland sediments (Murree and Siwalik Formations) exhumed by active structures in the Sub-Himalayan belt and from (2) metasediments and plutonic rocks exhumed in hinterland thrust sheets south of the Pir Panjal Range. Apatite (U-Th)/He (AHe) cooling ages for the molasses sediments are consistently younger than the sediment age indicating that Sub-Himalayan belt samples are reset. Single grain and mean age probability density plots reveal a period of rapid cooling and exhumation between 1.8–2.75 Ma throughout the Sub-Himalaya belt. AHe cooling ages in hinterland thrust sheets generally record older fault-related exhumation. Samples exhumed by the Main Central thrust (MCT) and Main Boundary thrust (MBT) yield single grain and mean ages between ~5–21 Ma. A nearby study further north in the hinterland, however, indicates young cooling (<3 Ma) across the Kishtwar Window. For Zircon (U‐Th)/He (ZHe) samples, most sample ages from the Sub-Himalaya are older or the same to the depositional age and are therefore detrital (unreset). Probability density plots of both Sub-Himalayan molasses and hinterland samples data show a pronounced spike in ZHe cooling between 16–21 Ma, a period where MCT motion is well documented throughout the Himalaya. Cooling patterns across the Kashmir Himalayas do not correlate with monsoon precipitation gradients, suggesting climate forcing is decoupled from erosion and exhumation. Distributed rather than localized break-forward deformation characterizes fault related exhumation for the orogenic wedge development in the Sub-Himalayan belt since at least ~2.75 Ma. In the hinterland, coeval young cooling across the Kishtwar Window, >100 km north of the deformation front, suggests in-sync tectonic-driven rapid exhumation across the orogenic wedge, coinciding with localities of predicted changing ramp geometry and/or active orogenic growth.