Abstract: The Xiannüshan Fault zone,lying along the western margin of Huangling anticline,is one of the most important fault zones in Three Gorges reservoir area. The fault experienced strong activities during Cenozoic. Whether the fault zone crosses the Yangtze River is one of the key problems in previous studies,as it has significant influence on the assessment of geological hazards and earthquake stability in the reservoir area. Based on tectonic and geomorphic observations along this fault zone around Baixianchi in Changyang County,Huangkou in Zigui County,together with the comparisons between the geology in Guizhou and Quyuan Town in the north bank of Yangtze River and the Xiannüshan Fault zone,it is suggested that the north end of this fault zone locates around Huangkou village and doesnt traverse the Yangtze River northward.
The details are as follows: ① On the basis of field data collection,it is found that the Xiannüshan Fault zone,which stretches 80km,underwent thrust movement in Cenozoic,resulting in ravines and fault scarps,topographically. Whereas,on the northern bank of Yangtze River,faults are rarely found,and most of the faults are developed in the Jurassic strata,without topographical effects. Therefore,the Xiannüshan Fault zone has not stretched to the north bank of Yangtze River.②Fault gouge and tectonite zone were found developed on Xiannüshan Fault zone at Baixianchi village,but only tectonite zone was found at Zhouping village. There are also some branch faults close to the northern end of the fault zone. So,the activity of the fault zone weakened from south to north in Cenozoic. The fault zone extends northward and dies out at Huangkou. It doesnt stretch forward any longer as indicated by continuous strata,sparse joints,and small folds,etc.

Key words: Three Gorges area, Xiannüshan Fault, tectonic landform

摘要： 仙女山断裂是三峡库区重要的断裂带之一,该断裂在新生代有过明显的活动。因其对三峡库区的地质灾害、地震稳定性有着重要影响,因此断裂是否穿过长江成为备受关注的热点问题。通过对仙女山断裂从长阳县白咸池到秭归县荒口一带断裂构造的野外地质调查,长江两岸构造地貌的对比,结合前人已有资料的分析发现: 仙女山断裂长约80km,将古生代地层逆冲到中生代地层之上,在长江南岸荒口以南断层形迹清楚,地貌上表现为沟谷和断层崖,而在荒口以北地区,地层连续、未见断错地貌现象; 与长江南岸断裂相比,江北的断裂多为小型断层,仅错断侏罗纪地层内的砂岩、泥岩,在地形上也无明显表现,不是仙女山断裂的延伸部分。综合分析认为,仙女山断裂带由南向北延伸至长江南岸荒口一带尖灭,没有向北延伸穿过长江。

关键词: 长江三峡, 仙女山断裂, 构造地貌