Characteristics of the Mesozoic and Cenozoic Tectonic Stress Fields of the Urumqi‐Usu Region, Xinjiang

Abstract

Abstract Based on the study of folds and related conjugate shear joints, the tectonic stress fields of the Urumqi‐ Usu region to the north of the North Tianshan Mountains have been reconstructed. Furthermore the author discussed the tectonic movements and their dynamic features. The early tectonic movement in the investigated region occurred from the end of the Late Jurassic to the initial stage of the Early Cretaceous, with the maximum (tensile) and minimum (compressional) principal stress trajectories in the tectonic stress field being in E‐ W and S‐ N directions respectively; the late tectogenesis took place from the end of the Early Pleistocene to the initial Middle Pleistocene, with the maximum and minimum principal stress trajectories in the late stress field striking in WNW and NE‐NNE directions respectively. Through computer‐aided simulated calculation by the finite element method and analysis of geological structure, it has been ascertained that the early tectogenesis is a nearly N‐S compressive movement and the late one a NE to nearly N‐ S compressive movement with reverse shear. The dynamic force which caused the tectogeneses came from the movement of the southern major fault, i.e. the North Tianshan Mountains.