Decoding the southeastern Tibetan Plateau growth: a 3D numerical simulation of Cenozoic crustal deformation

The southeastern Tibetan Plateau, an intracontinental deformation archetype recording oblique Indian-Eurasian convergence, has long been used to test geodynamic models of plateau growth. Driven by India's northward indentation, it has undergone multiphase deformation with kinematic and structural transitions. To explore its evolutionary dynamics, we developed 3D visco-elasto-plastic thermomechanical models reconstructing three tectonic stages: (i) crustal shortening; (ii) block lateral extrusion; and (iii) 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 has promoted decoupling, in which potential energy-driven ductile lower crustal flow affects 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 debate of geodynamics during continental collision.