The Kuqa late Cenozoic fold–thrust belt on the southern flank of the Tian Shan Mountains

The Kuqa fold–thrust belt (KFTB), a late Cenozoic fold–thrust belt on the southern flank of the Tian Shan Mountains, consists of several deformation zones trending nearly W–E. The main décollement fault of the KFTB gradually rises southwards. There are three regional main décollement faults in the Triassic dark mudstone, Paleogene gypsum salt (Kumugeliemu Formation), and Neogene gypsum salt (Jidike Formation), respectively, and possibly a fourth in the Jurassic coalbed. Laterally, thin-skinned structures are developed in the main segments of the KFTB, whereas thick-skinned structures are in the root zone. Vertically, the structural deformation above the Cenozoic gypsum-salt layers (Paleogene gypsum salt in the middle segment of the KFTB and Neogene gypsum salt in the eastern segment) is characterized by décollement folding, whereas that below is characterized by thrusting. The KFTB was resulted from the late Cenozoic intra-continental orogeny in the Tian Shan area under the far-field effect of the India–Asia collision. The deformation of KFTB began (folding and thrusting) ca. 23 Ma, when the far-field effect of the India–Asia collision reached the Tian Shan area. The deformation of KFTB accelerated ca. 10, 5–2, and 1–0 Ma. In general, the evolution of the KFTB is forward propagating, and the hinter parts of the KFTB continue to deform, while its front propagates southwards.