Late Quaternary crustal shortening rate of the Wensu fault-bend fold in the southern Tian Shan, NW China

Abstract

N‒S crustal shortening in the Tian Shan shows an obvious eastward decrease, which results in an eastward decrease in the width and uplift height of the topography. However, the highest peak in the Tian Shan region appears in its middle part (the Wensu area) instead of at the expected western end. At present, the kinematic information and N‒S crustal shortening rate of the Wensu foreland thrust system remain poorly constrained, which has led to controversy regarding the deformation characteristics and mechanism of geomorphic growth in this area. In this study, we focused on the kinematics and shortening rate of the Wensu fault-bend fold (WFBF), the frontal structural belt of the Wensu foreland thrust system. On the basis of interpretations of detailed high-resolution remote sensing images, field investigations, surveying of displaced terraces with an unmanned drone, the dating of late Quaternary sediments via OSL and trench excavation, we determined a relatively low N‒S crustal shortening rate of 1.31 ± 0.23 mm/yr over the past 24,000–40,000 years for the WFBF. We suggest that a listric thick-skinned fault geometry at depth results in more vertical uplift components, which is the key factor of significant topographic uplift amplitude in this region.