Multi‐Stage Cenozoic Cooling and Exhumation of the Northern Jinsha Region, Eastern Tibet: Insights From Low‐Temperature Thermochronology

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Abstract
The timing and mechanisms of Cenozoic deformation and landscape evolution in the eastern Tibetan Plateau remain contentious, particularly the roles of crustal shortening, strike‐slip faulting, and fluvial erosion. Here we integrate low‐temperature thermochronological data, including apatite fission‐track, apatite (U–Th)/He, and zircon (U–Th)/He ages, from the northern Jinsha region of eastern Tibet, between the low‐relief plateau interior and the deeply incised eastern margin. Our results reveal two broad phases of rapid cooling/exhumation: an early phase at ca. 68–45 Ma, with cooling rates of 4–10°C/Myr, broadly compatible with early Cenozoic crustal shortening and thickening; and a later phase at ca. 20–0 Ma, with cooling rates of ≥5°C/Myr. The three profiles record similar late Cenozoic cooling histories; therefore, the post–20 Ma signal cannot be uniquely attributed to local activity on the Jinsha Fault or to simple local river incision. Combined with published thermochronological data from the Jinsha River corridor, the results suggest a segmented regional cooling/exhumation pattern more compatible with fault‐influenced drainage organization and focused incision than with a single upstream‐propagating river‐incision wave. Between the two cooling/exhumation phases, the study area experienced prolonged thermal stability, or near‐isothermal holding, from 45 to 20 Ma, with cooling rates of <1°C/Myr. This interval is consistent with development and/or preservation of a high‐elevation, low‐relief landscape by the late Eocene to Oligocene. Overall, our results provide new constraints on the multi‐stage Cenozoic cooling/exhumation history of the northern Jinsha region and offer insight into the coupled tectonic and surface‐process evolution of eastern Tibet.

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