冀中坳陷廊固凹陷古近纪断层活动特征

ACTIVITIES OF PALEOGENE FAULTS IN LANGGU SAG,JIZHONG DEPRESSION

采用断层落差法和生长指数法计算冀中坳陷廊固凹陷活动断层的古落差和生长指数,绘制了凹陷各地质历史时期的古落差和生长指数平面分布图,并详细分析了各时期断层活动特征。分析研究可知,一级控凹断层大兴断层的活动存在分段性,整体上表现为自南西到北东逐渐减弱;孔店—沙四期,三级活动性断层主要集中在凹陷的东南部,但活动都比较弱;沙三—沙二期,活动性断层的分布整体向凹陷北东方向扩展,三级以上断层活动比较强。研究结果表明,古近纪廊固凹陷断层活动主要受控于构造演化背景,大兴断层对次级断层活动具有重要的影响。

By calculating the fault throw index and growth index of the active faults in Langgu sag,Jizhong depression, the fault throw figures and fault growth index figures of this sag in eachgeological time were drawn out. Research showed that Daxing fault had different activities atdifferent locations. The activity was weakened gradually from the southwest to the northeast as awhole. During the sedimentary period of Ek to Es4 , the three-level active faults were mainly locatedin the southeastern part of the sag, and were active weakly. During the sedimentary period of Es3 toEs2 , the distribution of active faults was gradually extended to northeast from the southeastern part ofthe sag, with intense faults activity. The results suggested that the activity of active faults inPaleogene was mainly controlled by structural evolution background, and the activity of other activefaults was also influenced by Daxing Fault.