Late Miocene extension of the Dali fault system in Southeast Tibet: Coupled tectonic inversion and landscape evolution

Abstract Tectonic inversion is often a dramatic event with significant implications, yet pinpointing its timing is challenging. The Red River fault, one of the most important high-strain structures in Southeast Tibet, experienced a kinematic reversal, but the exact timing remains debatable. The Dali normal fault system, situated at the northwestern end of the Red River fault, is kinematically linked to the right-lateral Red River fault. This linkage provides an excellent opportunity to unravel the timing of tectonic inversion. The Dali fault system also cuts across the hairpin-shaped reach of the Jinsha River, and its impact on river development would shed light on the landscape evolution influenced by normal faults. This study focuses on the Daju-Lijiang and Chenghai faults, two major branches of the Dali fault system, using zircon fission-track, apatite (U-Th)/He dating, and thermal modeling to reveal rapid exhumation in the footwalls starting at ca. 11–8 Ma and ca. 9–8 Ma, respectively. This shift indicates a tectonic transition from near east–west compression to east–west extension at the end of the Red River fault around the late Miocene (ca. 11–7 Ma), which is also supported by available data in the region. Furthermore, the normal faulting activity along the Daju-Lijiang fault since ca. 11–8 Ma neatly explains spatial and temporal variations in river incision between Tiger Leap Gorge and First Bend, which were influenced by oroclinal bending on the footwall. Tributary river profile analyses and geomorphic features show significant differences along the two sides of the Chenghai fault, which confirms the impact of normal faulting on differential incision of the Jinsha River. The mid–late Miocene transition in faulting styles appears widespread around the Chuan-Dian Block in Southeast Tibet, encompassing enhanced/weakened thrusting, the onset of strike-slip movements, and tectonic inversion. We propose that block translation relative to India’s northward advance and block rotation collectively induced stress field changes, leading to nearly synchronous tectonic adjustments in the Chuan-Dian Block during the mid–late Miocene. Overall, the Dali fault system exemplifies the coupled interplay between extensional deformation and fluvial landscape evolution.