Fluvial response to differential activity of the Litang fault system: Implications for fault kinematics and geodynamics in the southeastern Tibetan Plateau

Abstract

Understanding how active faults in the southeastern Tibetan Plateau accommodate the India-Asia collision is crucial for comprehending plateau growth and associated dynamic mechanisms. Previous studies mainly focused on major faults like the Xianshuihe-Xiaojiang and Red River faults bounding the Chuan-Dian crustal block. However, the evolution of secondary faults within this block remains largely unknown. This study examines the NW-trending Litang fault, the largest secondary sinistral-slip fault with a normal component in the Chuan-Dian block, to evaluate its variations in tectonic activity and kinematics through fluvial geomorphic analyses. Results from hypsometric integral, channel steepness, and knickpoint analyses reveal varying activity across four segments of the Litang fault (Cuopu, Maoya, Litang, and Jiawa, from northwest to southeast), with Maoya being the most active at the center. River profile modeling suggests that faulting-perturbed river incision began at 0.3–0.4 and 0.6–0.7 Ma in the Cuopu and Maoya segments, respectively; while those in the Jiawa segment in the southeast started at 1.8–2.2 Ma, much earlier than those in the northwest. These findings suggest the northwestward younging or propagation of oblique-slip faulting on the Litang fault. Incorporating the Litang fault's geometry as one branch of the Batang-Litang V-shaped conjugate strike-slip fault system, along with previous interpretations of regional geodynamics, our results suggest that the Litang fault remains immature. Its Quaternary kinematic pattern is likely associated with horizontal shearing at the base of the upper crust or lithosphere.