Abstract The southeastern Tibetan Plateau, an intracontinental deformation archetype recording oblique Indian-Eurasian convergence, has long tested the end-member models of block extrusion and lower crustal flow. Driven by India’s northward indentation, it has undergone multi-phase deformation with kinematic and structural shifts. To explore its evolutionary dynamics, we developed 3D visco-elasto-plastic thermomechanical models reconstructing three tectonic stages: (1) crustal shortening, (2) block lateral extrusion, and (3) kinematic reversal in the southeastern Tibetan Plateau. Simulations show that strain localization along large-scale shear zones is initially controlled by lithospheric heterogeneities enabling rigid block extrusion. Since the mid-late Miocene, vertically stratified crustal rheology promotes decoupling, in which potential energy-driven ductile lower crustal flow modulates upper crustal deformation and triggers kinematic reversal. This transition reconciles block extrusion and lower crustal flow, which operate sequentially rather than exclusively and are modulated by temporal variations in crustal rheology and boundary conditions, resolving the long-lasting debates of geodynamics during continental collision.
Wang et al. (2026) studied this question.