Late Quaternary thrust faulting along the NW-trending Heya fault in southwestern Tian Shan, NW China

Abstract

Along both the northern and southern flanks of the Tian Shan orogenic belt, a series of foreland thrust systems have been developed to accommodate N – S crustal shortening. The strikes of these foreland thrust systems are roughly parallel to the mountain range and have usually been viewed as a result of outward expansion of the Tian Shan orogenic belt. However, the NW-striking Heya fault (HYF) in the southern Tian Shan piedmont has been identified, but at present, its late Quaternary kinematics, deformation mechanism and role in regional tectonic deformation are still unclear. In this study, based on interpretations of detailed high-resolution remote sensing images, field investigations, surveys of displaced terraces with an unmanned drone, dating of late Quaternary sediments via optically stimulated luminescence (OSL) and trench excavation, we quantified the structural geometry and determined the ∼0.85 mm/yr crustal shortening rate of the HYF. A survey of the displaced geomorphic surfaces implies that the HYF obeys a characteristic slip model. We suggest that the low-angle thrust HYF is a contractional horsetail structure located near the easternmost end of the Maidan fault and accommodates its left-lateral strike-slip motion.