Multi-stage growth of Southeast Tibet since the Late Cretaceous: Insights from the Jinsha suture zone in the Three Rivers region

[1]¿p#1 Reconstructing the deformation and growth history of Southeast Tibet is critical for understanding continental lithospheric dynamics and its far-reaching impacts on the East Asian monsoon, biodiversity hotspots, and river network evolution. However, the spatiotemporal pattern of plateau growth and underlying mechanisms remain debated. Here, we investigate the northern Jinsha River fold-and-thrust belt, an inherited structure of the Jinsha suture zone, using low-temperature thermochronology and thermal modeling to constrain its deformation and exhumation history. Our results reveal three accelerated exhumation episodes: Late Cretaceous (ca. 80–68 Ma), Late Eocene (ca. 40–34 Ma), and Early Miocene (>19 Ma) to present. The Late-Cretaceous phase correlates with syn-tectonic sedimentation in the Gonjo Basin, suggesting a coupled tectono-sedimentary system. Regional synthesis reveals widespread Late Cretaceous to Early Cenozoic rapid exhumation in eastern and central Tibet, highlighting the role of Neo-Tethyan subduction and initial India-Asia collision in shaping early topographic relief. The Late-Eocene pulse coincides with magmatism along the reactivated Jinsha suture zone and regional uplift, reflecting a major compressional deformation event. Early-Miocene exhumation (150–300 m/Myr) is linked to Jinsha River incision. Integrating our new constraints with published deformation records, we identify a pattern of southeastward propagation of compressional deformation since the Late Eocene in northern SE Tibet, supporting stepwise plateau growth through crustal shortening. We also observe a potential second phase of southeastward-propagating deformation since the Early Miocene, consistent with an eastward-younging trend in river incision, although this inference carries considerable uncertainties. Overall, this work provides valuable insights into the expansion pattern of southeast Tibet.