新疆南天山库车坳陷晚第四纪以来地壳缩短速率的初步研究

PRELIMINARY STUDY OF LATE QUATERNARY CRUSTAL SHORTENING RATE ALONG KUQA DEPRESSION IN SOUTH TIANSHAN, XINJIANG

库车坳陷是南天山中段新构造运动异常强烈的地区，发育4排近EW向展布的逆断裂-背斜带。通过野外实地考察及前人资料分析，认为该区晚第四纪以来的构造变形主要集中于喀桑托开逆断裂-背斜带、秋里塔格逆断裂-背斜带和最南缘的亚肯逆断裂-背斜带之上，而且不同构造带之间的变形方式存在较大差异。作者利用全站仪（totalstation）对上述构造带的变形地貌进行了精确测量，并结合年代学分析，得到喀桑托开逆断裂一背斜的地壳缩短速率为1．0—2．0mm／a，秋里塔格逆断裂一背斜带的地壳缩短速率为2．5—3．0mm／a，亚肯盲逆断裂一背斜的地壳缩短速率为1．5—2．0mm／a。晚第四纪以来，库车坳陷SN向总的地壳缩短速率不＜5．0—7．0mm／a。

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 character/stic and the slip rate. Based on the deformation characteristics of conceptual fauh-propagation fold and field investigation, we think the deformation of the faultpropagation 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.