Late Cretaceous-Paleogene Exhumation History and Evolution of Paleotopography in the Gaize Basin, Central Tibet.

A series of terrestrial sedimentary basins along the Bangong-Nujiang Suture Zone (BNSZ) record a wealth of information regarding the uplift and geomorphological evolution of the central Tibetan Plateau. The uplift, exhumation, and sedimentation processes in these basins and the surrounding orogenic belts are of significant scientific importance for understanding the tectonic evolution of the central Tibetan Plateau. Taking the Gaize Basin as the research focus, low-temperature thermochronology and thermal history modeling were conducted on sandstone samples to analyze their exhumation history and driving mechanisms during the Late Cretaceous to Paleogene. Based on stratigraphy and the youngest detrital zircon ages, the samples were collected from the Upper Jurassic to Lower Cretaceous Shamuluo Formation; thermal history modeling using apatite and zircon (U-Th)/He (AHe/ZHe) results reveals two significant exhumation events: 87-70 and 56-26 Ma. The rapid cooling-exhumation event during the Late Cretaceous is associated with crustal shortening and thickening caused by the collision of the Lhasa-Qiangtang terrane; the Paleogene exhumation event is linked to tectonic uplift driven by the India-Asia collision and the continued northward subduction of the Indian continent. Continuous thrusting and uplift on both sides of the basin strengthened river cutting and erosion and gradually converted the external drainage system to an internal drainage system, and the high-relief terrain was progressively leveled and filled. The height of the surface uplift brought on by sediment accumulation was approximately 0.4 km. After Oligocene, high-altitude, low-relief terrain had already been established.