Denudation pattern across the Longriba fault system and implications for the geomorphological evolution of the eastern Tibetan margin

- We document the denudation pattern across the Longriba fault system, east Tibet, with 10Be concentrations in river sediments
- A threefold increase in denudation rates across the LFS highlights its importance as a geomorphological boundary
- The LFS restrains the headward propagation of the drainage network into the low relief of the Tibetan Plateau

Following the 2008 Wenchuan earthquake (Sichuan, China), the dextral strike-slip Longriba fault system (LFS) has been recognized as a main intracontinental structural boundary within the eastern Tibetan Plateau. While numerous studies have focused on the Longmen Shan frontal range to constrain the dynamics of the eastern Tibetan margin, little is known on the LFS, particularly on its eventual influence on the geomorphological evolution of the latter. Here, we provide a new data set of denudation rates derived from beryllium-10 concentrations in river sediments from 33 medium-sized catchments. Our sampling area covers the frontier between the dissected margin and the low relief interior plateau. Our results reveal a sharp increase of denudation across the LFS, from < 0.1 mm/y in the Ruoergai basin to 0.3 mm/y toward the Longmen Shan range. Such denudation pattern indicates a major morphotectonic control of the fault system on the eastern Tibetan margin evolution. Additional topographic analysis confirms the role of the LFS as an important geomorphological boundary, restraining the westward propagation of river incision into the low-relief areas, thus partly preventing the dismantling of the eastern Tibetan Plateau.