Cenozoic Crustal Shortening and Structural Transition in the NW Yunnan Basin Region, SE Tibetan Plateau

Abstract Striking changes in kinematics and deformation styles often occur in convergent orogens in the later stages of their tectonic evolution, such as in the southeastern Tibetan Plateau, which transitioned from transpression to transtension and experienced kinematic reversal on regional fault systems since the Miocene, approximately 40 Ma after the initial collision. This shift has long been identified, but the spatial patterns of onset and driving mechanisms are controversial, hindering an understanding of the processes and dynamics of intracontinental orogeny. This issue is addressed for the NW Yunnan basin region in the SE Tibetan Plateau, by an integrative study of apatite (U‐Th)/He and fission track thermochronology along with structural and sedimentary analysis. Late Eocene to Oligocene/early Miocene approximately E‐W shortening resulted in thrust and fold systems, widespread exhumation, and topographic uplift. Combined with existing data, this region underwent a transition to transtension during the late Miocene‐Pliocene, forming basin‐and‐range style landscapes. The crustal deformation and kinematics of major active faults based on newly processed geophysical data indicates crustal thickening in a hyper‐oblique convergent zone may have raised the crustal temperature at depth and weakened the long‐term strength of the lower crust and upper mantle, especially in the presence of water. Such lithospheric conditions are more prone to localized tectonics and can cause late‐stage orogenic gravitational collapse, driving striking structural transition in the NW Yunnan basin region.