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

摘要

We determined vertical components of slipnrates of 0.22 ± 0.03 mm a–1 for the Jiayuguannfault and 0.11 ± 0.03 mm a–1 for the JintanannShan fault, which lie along the northeasternnedge of the Tibetan Plateau and in the westernnHexi Corridor (Northern Qilian Shan,nChina). We used structural investigations,nair-photo imagery analysis, topographicnprofi ling, optically stimulated luminescencen(OSL) dating, and 10Be exposure dating. Tonquantify the slip rates along the faults, wenidentifi ed and surveyed the well-preservednfault scarps, and we sampled quartz-richnpebbles and cobbles on fan surfaces andnwithin ~2-m-deep pits to determine surfacenexposure ages and pre-depositional inheritance.nOur slip rates pertain to the pastn~115 ka. They are consistent with previousngeological and GPS constraints that suggestnthat NNE–SSW shortening across the northeasternnTibetan Plateau has been distributednonto several active faults and that shorteningnis partitioned into low slip rates of 1 mm a–1non each fault. We infer that the decreasingnslip rate from 95 E eastward to the easternnend of the Altyn Tagh fault and the low slipnrates of these thrust faults are related. Thentotal shortening in the direction parallel tonthe Altyn Tagh fault in the Yumen Basinnof 0.90–1.43 mm a–1 attests that left-lateralnstrike slip at the eastern end of the fault hasnindeed been absorbed by deformation withinnthe Yumen Basin. We infer that the TibetannPlateau continues to grow northeastwardnby thrust faulting at low rates and by foldingnon the northeastern edge of the HexinCorridor basin.