涉县盆地控盆构造晚第四纪活动特征

Characteristics of Basin Controlling Structure of Late Quaternary Activity in Shexian Basin

摘要:

涉县断裂为太行山隆起区内涉县盆地的控盆构造，走向由NE转为近EW向，倾向NW/N，中部在井店东被EW向断裂错断，是控制涉县盆地的一组断裂。本文采用地质地貌调查、河流阶地分析和地质测年等方法，研究了涉县断裂晚第四纪活动特征。研究发现，涉县断裂带由多组断裂构成，带宽约200m，在清漳河两侧表现为山前的陡崖地貌、基岩破碎变形带，具有正断兼走滑特征，在基岩变形带上部发育走向NNE向和NWW向次级滑动面，次级滑动面错断第四系黄土，最新活动到晚更新世；断裂在盆地区通过，地表形成低缓陡坎，断裂错断Q_2-3地层，表现为上陡下缓的正断层。通过对涉县断裂两侧清漳河河流阶地、夷平面和地层年龄综合分析，估算涉县断裂晚更新世以来平均垂直滑动速率为0.06~0.08mm/a，中更新世以来平均垂直滑动速率为0.22~0.34mm/a，垂直差异活动主要发生于中更新世期间。

Abstract:

Shexian Fault is the basin controlling structure of Shexian Basin in the Taihang mountain uplift area. Its strike changes from NE to EW and tends to NW/N,the middle segment is staggered by the east-west fault in the east of Jingdian,with a bandwidth of about 200m. In this paper,the late Quaternary activity characteristics of Shexian Fault are studied by means of geological geomorphological survey,river terrace analysis and geological dating. It is found that when the Shexian fault passes through the bedrock area,it is characterized by steep landform in front of the mountain and broken deformation zone of the bedrock,with positive fault and strike slip characteristics. In the upper part of the deformation zone of the bedrock,there exist NNE and NWW trending secondary sliding surfaces,which offset the Quaternary loess as late as to late Pleistocene. When the fault passes through the basin area,there is a gentle-slope scarp on the surface. The late Pleistocene strata are cut by steep upper and gentle lower normal faults. Based on the comprehensive analysis of Qingzhanghe river terrace,planation plane and stratum age on the two sides of Shexian Fault,it is estimated that the average vertical slip rate of Shexian Fault is 0.06~0.08mm/a since the early Late Pleistocene,and 0.22~0.34mm/a since the Middle Pleistocene,respectivelly.