Northeastward thrust propagation accommodated by the Minle oblique ramp at the northern edge of the Qilian Shan in the northeastern Tibetan Plateau

Abstract

The different segments of thrust faults are typically connected by linking faults (e.g., lateral ramps, tear faults, or oblique ramps) that accommodate the differential movement and transfer stress in step-over zones. However, the activities and deep structures of linking faults on the Tibetan Plateau have received limited attention in previous studies. The Minle Fault, a strike-varying oblique ramp on the northeastern margin of the Tibetan Plateau, offsets multiple terraces of the Yudai and Hongshui Rivers and accommodates the deformation in the step-over zone between two thrust faults. In this study, 132 vertical offsets and partial strike-slip offsets along the Minle Fault were measured based on high-precision DEM, a terrace chronology framework was established using AMS ¹⁴C dating, and a 2D kinematic model was constructed based on the surface fault offsets. The results indicate linear increasing vertical offsets along strike on each terrace, a listric deep structure with a flat detachment depth of ∼2.5 km, and a late Quaternary dip-slip rate of ∼1.1 mm/a for the Minle Fault. The Minle Fault, a thin-skinned oblique ramp formed during the Quaternary following the protrusion of the Yumu Shan, poses a potential earthquake hazard. On the actively growing Tibetan Plateau dominated by large strike-slip and thrust faults, the linking faults between them serve as critical adjusted structures, constituting an essential component in the evolution of the orogenic belt.