The Time of Deformation on the Kuqa Fold-and-Thrust Belt in the Southern Tianshan-Based on the Kuqa River Area

The Tianshan is one of the largest and the most active intracontinental mountain ranges in the world. Ac-tive fold-and-thrust belts flank both sides of the mountain. This paper based on the data of seismic refection profiles, wells, remote sensing, detailed surface structural survey and magnetostrati graphy focuses on the Kuqa thrust system in the central part of the southern Tianshan. In the Kuqa River area, the 60 km wide fold-and-thrust belt is characterized by four east-west-trending folds. Near the mountain front, the Northern fold and the Keyi fold involve Mesozoic and Eogene strata and make two unconformities between the Meocene Jidike Formation and the Eogene Suweiyi Formation and in the Meocene Kangcun Formation. The unconformities im-ply that the beginning of deformation in the Kuqa thrust system is around Oligocene. Toward the Tarim basin, the more recent Miocene to Pleistocene sediment is folded along the Quilitake anticline. Further south, the Yaken anticline is involving the Holocene surface that is folded. The growth strata over the Yaken anticline and the Quilitake anticline are in the lower part of the Pliocene Kuqa Formation. Combining with the magne-tostratigraphic sections on the both sides of the Qiulitake anticline we suggest that the timing of deformation on the Yaken anticline and the Quilitake anticline is the early Pliocene (5. 5 ± 0. 2 Ma), and an average slip rate of 1. 5 mm/a since Pliocene is estimated on the Quilitake anticline.