渤海湾盆地冀中坳陷高阳低凸起构造特征及成因机制

Structural characteristics and genetic mechanism of Gaoyang low uplift in Jizhong Depression, Bohai Bay Basin

高阳低凸起位于渤海湾盆地冀中坳陷中部,其形成演化与相邻的保定、饶阳等凹陷的发育密切相关。剖析高阳低凸起的构造特征,将为整体研究冀中坳陷中部伸展变形系统提供重要依据。基于丰富的地震资料,运用构造解析方法,厘定高阳低凸起的构造发育特征;根据钻井分层,并结合区域地层对比,明确同构造期地层的时代及构造发育时间;通过编制平衡剖面,开展区域构造演化分析,探讨高阳低凸起成因机制。研究表明,高阳低凸起整体表现为由南向北逐渐变窄的宽缓背斜,并且西翼陡、东翼缓;凸起东侧发育有多条规模较大的NW—SE向断层,西侧发育的断层数量少且规模小;研究区南部发育的断陷期地层时代最老为晚中生代,北部为古新世。高阳低凸起为发育于冀中坳陷中区两侧边界断层共同上盘的“双向旋转型”滚动背斜,其形成演化主要受控于两侧边界断层的伸展活动,凸起南部开始发育的时间早于北部。

As a secondary structural unit locating in the central Jizhong Depression of the Bohai Bay Basin, the formation and evolution of Gaoyang low uplift is closely related to the development of the adjacent Baoding and Raoyang sags. The understanding for the structural characteristics of the Gaoyang low uplift is valuable for the overall study of the extensional deformation system in the central Jizhong Depression. Based on abundant seismic data, the structural characteristics of the Gaoyang low uplift were determined by using structural analysis method. According to drilling data and regional stratigraphic correlation, the age of syndepositional formation and the time of tectonic activity were determined. By compiling balanced sections and analyzing regional tectonic evolution, the genetic mechanism of the Gaoyang low uplift was discussed in this paper. The Gaoyang low uplift is featured by a gentle anticline which narrows from the south to the north, and the west limb of the anticline is steeper than the east counnterpart. Several NW-SE trending faults with large heave and long plane extension distance developed in the east flank of the Gaoyang low uplift, while only a few small-scale faults were developed in the west flank. The age of the oldest syndepositional strata in the southern part of the studied area is the Late Mesozoic, while that in the north is Paleocene. The Gaoyang low uplift is a compound rollover anticline developed in the common hanging wall of the boundary faults on both sides of the central Jizhong Depression, and its formation was mainly controlled by the extension of the boundary faults. The southern Gaoyang low uplift began to develop earlier than the northern part.