Low‐Temperature Thermochronology of the Indus Basin in Central Ladakh, Northwest India: Implications of Miocene‐Pliocene Cooling in the India‐Asia Collision Zone

Abstract

AbstractThe India‐Asia collision zone in Ladakh, northwest India, records a sequence of tectono‐thermal events in the interior of the Himalayan orogen following the intercontinental collision between India and Asia in early Cenozoic time. We present zircon fission track, and zircon and apatite (U‐Th)/He thermochronometric data from the Indus Basin sedimentary rocks that are exposed along the strike of the collision zone in central Ladakh. These data reveal a postdepositional Miocene‐Pliocene (~22–4 Ma) cooling signal along the India‐Asia collision zone in northwest India. Our zircon fission track cooling ages indicate that maximum basin temperatures exceeded 200°C but stayed below 280–300°C in the stratigraphically deeper marine and continental strata. Thermal modeling of zircon and apatite (U‐Th)/He cooling ages suggests postdepositional basin cooling initiated in Early Miocene time by ~22–20 Ma, occurred throughout the basin across zircon (U‐Th)/He partial retention temperatures from ~20–10 Ma, and continued in the Pliocene time until at least ~4 Ma. We attribute the burial of the Indus Basin to sedimentation and movement along the regional Great Counter thrust. The ensuing Miocene‐Pliocene cooling resulted from erosion by the Indus River that transects the basin. An approximately coeval cooling signal is well documented east of the study area, along the collision zone in south Tibet. Our new data provide a regional framework upon which future studies can explore the possible interrelationships between tectonic, geodynamic, and geomorphologic factors contributing to Miocene‐Pliocene cooling along the India‐Asia collision zone from NW India to south Tibet.