渤海湾新生代盆地的两种构造系统及其成因解释

Two tectonic systems in the Cenozoic Bohai Bay basin and their genetic interpretation

渤海湾古近纪盆地可以划分为3个裂陷带和1个裂陷区,都分布在上地幔隆起部位。盆地构造变形可以分为伸展构造和走滑构造两个相对独立、相互关联的新生代构造系统。伸展构造由不同尺度的伸展断层和与伸展断层垂直或斜交的变换断层构成连锁断层系统,在盆地区具有分散的透入性特点,并控制着古近纪断陷的分布和演化。在伸展构造变形基础上叠加了3条北北东向—北东向右旋走滑断裂(带),后者及其伴生构造组成盆地中的呈带状展布的新生代走滑构造系统。伸展构造是一种“水平层状的”薄皮构造。正断层向深部收敛或终止于中地壳内的拆离断层面上。走滑构造是一种“垂直带状的”厚皮构造。浅层的走滑断层以多种方式并入到深断裂带中。这两种构造系统是盆地区新生代时期主动裂陷和被动裂陷两种作用机制的具体表现。

The Paleogene Bohai Bay basin may be divided into three rift zones and one rift area,which corre - spond to the updoming zone of the upper mantle.The tectonic deformation in the basin may be classified into two relatively independent and interconnected Cenozoic tectonic systems:the extensional tectonic system and strike-slip tectonic system.The extensional tectonic system is a linked fault system formed by extensional faults of different scales and transform faults perpendicular or oblique to the extensional faults.In the basin they are dis - persed and penetrate into the upper crust and control the distribution and evolution of the Paleogene rifting.Three NE-NNE right-lateral strike-slip faults are superposed on the extensional system.These strike-slip faults and their associated structural elements form the Cenozoic strike-slip tectonic system.The extensional system is a “ horizontal layered ” thin-skinned tectonics at the crustal scale.The normal faults converge toward great depths or terminate at the detachment fault surfaces within the mid-crust.The strike-slip system is a “ vertical belt-like “ thick-skinned tectonics at the crust scale.The strike-slip faults at the shallow level of the crust are merged into the deep fault zones in several ways.The two tectonic systems are concrete manifestations of the active rifting and passive rifting mechanisms in the basin during the Cenozoic.