渤海海域渤南地区新生代断裂体系与盆地演化

摘要

Abundant 3D seismic data were used, combined with the characteristics of seismic profile and time slices, the fault development and basin structure of Bonan area were researched. Furthermore, characteristics of the fault system and the structural evolution were delineated. The Cenozoic Tanlu fault in Bonan area was divided to eastern, middle and western branches. These branches interact with the EW-trending, NW-trending and NE-trending were associated with the strike-slip movement of the Tanlu fault, leading to the formation of the grid structural pattern in Bonan area due to changing stress field. There fore, changes in the relative importance between extension and strike-slip occurred in Bonan area. The Cenozoic structural evolution can be classified into three evolutionary stages, i.e., left lateral slip with strong extension, right lateral slip with strong extension and weak slip and weak extension. During the first stage of Ek-Es4, the Eastern Branch moved greatly but the Middle and the Western Branch weakly. The EW-trending, NW-trending controlled the basin pattern of the Huanghekou Sag and Laizhouwan Sag. During the second stage of Es3-Ed, three branches of the strike-slip fault and the main faults of other directions became activated. The secondary faults of the NE-trending and the near EW-trending faults began to develop. The two basins underwent persistent extension and rift. During the third stage of Ng-Nm, right-lateral strike-slip changed to weak, en-echelon faults of the NE-trending faults that appeared near the Middle and Western Branch, and secondary faults were increasingly developed. Two basins were transformed into initial rift.%利用现今丰富的三维地震资料，将地震剖面解释与相干切片分析相结合，对渤海海域渤南地区断裂发育与盆地结构进行研究，明确了断裂体系及构造演化特征。结果表明：新生代郯庐断裂渤南段可分为东、中、西三支，并与受郯庐走滑断裂影响的近EW向、NW向和NE向主干断裂体系共同组成了渤南地区网格状的构造格局；而区域应力背景的改变导致渤南地区走滑和伸展作用的强弱发生了变化，使得构造演化可划分为左旋走滑-强伸展、右旋走滑-强伸展和弱走滑-弱伸展三个阶段，第一阶段孔店组~沙四段郯庐断裂东支强烈活动，中支和西支活动微弱，NW向和近EW向大断裂活动形成了黄河口凹陷和莱州湾凹陷的盆地格局；第二阶段沙三段~东营组走滑断裂三支及其他方向主干断裂均活动，NE向和近EW向次级断裂开始发育，各盆地持续性伸展断陷；第三阶段馆陶组-明化镇组右旋走滑减弱，郯庐断裂中支和西支发育呈一系列NE向雁列断层，东支及其他方向主干断裂附近次级小断层继续增多，各盆地转为了整体的坳陷。