Determination of the Timing of Active Structures in Haiyuan-Liupan Shan Area: Constraints from OSL Dating

Haiyuan-Liupan Shan area is located in the northeastern margin of present Tibetan plateau.The study of the active structures in this area will provide constraints not only for the seismic evaluation but also for the northeastward growth of the plateau.Based on the geological survey and optically stimulated luminescence(OSL) dating,the timing of the active structures has been determined.The results indicate that active structures occurred in Late Quaternary along the Haiyuan-Liupan Shan and Xiangshan-Tianjing Shan faults,forming the structures such as angular unconformity(planation surface),fold and fault.This suggests that Haiyuan-Liupan Shan area should be considered as a focus of seismic evaluation,and also that the Tibetan plateau grew in its northeast margin in Late Quaternary.