苏北盆地高邮凹陷边界断裂带构造特征及成因

真武、吴堡断裂带是高邮凹陷的边界断裂带,具有复杂的结构和演化特征。通过三维地震资料解释以及断层平均活动速率的计算,分析了两断裂带在晚白垩世-新生代时期的几何学和运动学特征,将两断裂带作为一个整体,建立了凹陷边界主断裂发育的时空关系,对比探讨了两断裂带内各级断层的发育顺序和模式,并探讨了断层发育的成因。研究表明:一级断裂真①、吴①断层形成于泰州组沉积时期,阜四段沉积时期达到活动顶峰。二级断裂真②、吴②断层形成于阜四段沉积时期,戴南组沉积时期达到活动的顶峰。二级断裂主要形成于一级断裂沿走向的转折处,其延伸方向受控于区域早期NW-SE向伸展应力以及曲折边界条件;两断裂带内部断层发育模式有很大不同,认为其分别形成于伸展机制与斜滑机制下,与区域后期EW向挤压导致的郯庐断裂带右旋走滑作用有关。

Structural Characteristics and Origin of Boundary Fault Belts of the Gaoyou Sag in the Subei Basin

As the boundary of the Gaoyou Sag, the Zhenwu and Wubao Fault Belts show complicated geometry and evolution history. Based on 3D seismic interpretation and calculation of mean fault active rate, we analyze the geometric and kinematic characteristics of the two fault belts during Late Cretaceous-Quaternary and establish the temporal-spatial relationship of development of the main faults as a whole. We also investigate the development patterns and the formation processes of the two fault belts respectively. Our results show that the main boundary faults of the Gaoyou Sag were formed during the deposition of the Funing and Dainan Formations and might have been related to the NW-trending subduction of the paleo-Pacific Plate, which caused the NW-SE trending regional extension in East China. In particular, the trends and the formation patterns of the Zhen②、Wu② and Ji3 Faults are related to the boundary conditions. We also infer that the Zhenwu and Wubao Fault Belts are formed through different mechanism. The Zhenwu Fault Belt was formed by stretching while the Wubao Fault Belt was formed via an oblique slip mechanism which maybe related to the dextral strike-slip of the Tanlu Fault. The dextral strike-slip of the Tanlu Fault maybe connected with the regional EW-trending compression induced by orthogonal subduction of the paleo-Pacific Plate.