Late Quaternary slip rates of the thrust faults in western Hexi Corridor (Northern Qilian Shan, China) and their implications for northeastward growth of the Tibetan Plateau

Abstract

We determined vertical components of slip rates of 0.22 +/- 0.03 mm a(-1) for the Jiayuguan fault and 0.11 +/- 0.03 mm a(-1) for the Jintanan Shan fault, which lie along the northeastern edge of the Tibetan Plateau and in the western Hexi Corridor (Northern Qilian Shan, China). We used structural investigations, air-photo imagery analysis, topographic profiling, optically stimulated luminescence (OSL) dating, and Be-10 exposure dating. To quantify the slip rates along the faults, we identified and surveyed the well-preserved fault scarps, and we sampled quartz-rich pebbles and cobbles on fan surfaces and within similar to 2-m-deep pits to determine surface exposure ages and pre-depositional inheritance. Our slip rates pertain to the past similar to 115 ka. They are consistent with previous geological and GPS constraints that suggest that NNE-SSW shortening across the northeastern Tibetan Plateau has been distributed onto several active faults and that shortening is partitioned into low slip rates of <= 1 mm a(-1) on each fault. We infer that the decreasing slip rate from 95 degrees E eastward to the eastern end of the Altyn Tagh fault and the low slip rates of these thrust faults are related. The total shortening in the direction parallel to the Altyn Tagh fault in the Yumen Basin of 0.90-1.43 mm a(-1) attests that left-lateral strike slip at the eastern end of the fault has indeed been absorbed by deformation within the Yumen Basin. We infer that the Tibetan Plateau continues to grow northeastward by thrust faulting at low rates and by folding on the northeastern edge of the Hexi Corridor basin.