Cenozoic exhumation history and deformation mechanisms in eastern Tibet: Constraints from low-temperature thermochronology

Uplift, deformation, and denudation govern the topography and geomorphology of mountain belts. Because mountain ranges vary markedly in their tectonic setting and geology, they also exhibit distinct deformation styles and histories. The eastern Tibetan margin, located adjacent to the Sichuan Basin, offers critical insight into plateau growth and deformational behavior. The northern and south-central segments of the Longmen Shan along the eastern Tibetan margin differ substantially in geomorphology and deformation patterns, implying distinct evolutions and deformation mechanisms. To explore this, we employed systematic low-temperature thermochronology to reconstruct the uplift history of the northern and south-central segments of the eastern Tibetan margin. Our results show that the northeast-striking central Longmen Shan, located within the present-day Pengguan complex area, has experienced faster uplift and erosion since ca. 40 Ma than adjacent regions. This rock cooling and erosion pattern implies that channel flow−driven crustal deformation has dominated within the central Longmen Shan since that time. From ca. 40 Ma to 20 Ma, the northern Longmen Shan exhibited regional uplift and erosion, largely controlled by regional fault activity. Since ca. 10 Ma, the central Longmen Shan bounded by the Longriba and Guanxian-Anxian faults experienced pronounced cooling, implying episodes of rapid exhumation. By contrast, the northern segment during this time saw localized rapid exhumation adjacent to major faults. Together, these observations indicate a contractional regime in the central and southern Longmen Shan and a strike slip−dominated regime in the northern segment since at least ca. 10 Ma.