关键词: 库车坳陷, 晚第四纪, 地壳缩短, 南天山

Abstract: The Kuqa depression is located in the middle segment of the southern Tianshan Mountains. There are four E-W extending rows of reverse fault and anticline zones in the depression. From the south Tianshan Mountains towards the Tarim basin, they are the mountain piedmont, the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. After a month field working, we find the crustal shortening of the Kuqa depression in late Quaternary is almost caused by the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. The reverse fault and anticline zones in the Kuqa depression are very different in tectonic feature. We accurately surveyed these tectonics with total station and differential GPS in order to get a new cognition of the deformation characteristic and the slip rate. Based on the deformation characteristics of conceptual fault-propagation fold and field investigation, we think the deformation of the fault-propagation fold in the Kuqa depression is caused by faulting rather than folding. The crustal shortening rate caused by the fault is approximately near to the actual rate. So we only surveyed the deformation near the fault. The Kasangtuokai anticline is a fault-propagation fold. From late Quaternary, the deformation of Kasangtuokai anticline is mainly caused by total-uplift of the hanging wall. The deformation rate is about 1.0～2.0mm/a. The deformation feature of the Dongqiulitag anticline is similar to that of the Kasangtuokai, while the crustal shortening rate is little more than that of Kasangtuokai, about 2.5mm/a. The Qiulitag anticline is a very complicated tectonic. It is a fault-bend fold. There are two reverse faults on the core and the north limb of the Qiulitag anticline. Its tectonic deformation includes two parts: the fold rise and the uplift of the hanging wall of the fault. By surveying and dating, we get the crustal shortening rate of the Qiulitag anticline limb of about 1.06～2.0mm/a. Considering the shortening of the core fault and southern limb, the total rate is possibly more than 3.0mm/a. The Yaken anticline is a blind thrust fault-anticline fold. Its shortening rate is 1.5～2.0mm/a. So the total crustal shortening rate of the Kuqa depression is more than 5.0～7.0mm/a from late Quaternary.

Key words: Kuqa depression, late Quaternary, crustal shortening, southern Tianshan