A fluvial record of fault-propagation folding along the northern Qilian Shan front, NE Tibetan Plateau

Abstract

The kinematics of thrust fault is key to understand the deformation and uplift of mountain ranges. Along the northern front of the central Qilian Shan mountain range, the NE Tibet Plateau, a flight of terraces developed along the Red Sand River were deformed above a growing fault-propagation fold. Via luminescence and 10Be exposure dating, abandonment ages of the terrace surfaces were determined to be 100.9 ± 5.8 ka BP for T9, 88.7 ± 7.0 ka BP for T8, and 68.8 ± 7.6 ka BP for T7. Terrace profiles measured by differential GPS across the monocline were used to constrain the recent fold deformation, and the trishear model was applied to estimate the fault slip rate and thrust history. We thus derived an average slip rate of 1.3 ± 0.1 mm/a for the Heihekou (HHK) fault since ~90 ka BP. In addition, our results imply that the onset of the HHK fault occurred at 0.8–1.4 Ma, indicating a recent northeastward propagation of the active thrust faulting of the North Qilian Shan Fault (NQF). Our results also indicate uniformly distributed slip along the western, central, and eastern segments of the north Qilian Shan. Due to the different thrust kinematics along the NQF, the uplift rate is not uniformly distributed along the hanging wall of the thrust.