渤海湾盆地西部保定凹陷构造一地层层序与盆地演化

Tectono-stratigraphic sequence and basin evolution of Baoding sag in the western Bohai Bay Basin

保定凹陷位于渤海湾盆地内冀中坳陷的西部，西侧以太行山山前断层为界与太行山隆起相隔。凹陷内构造一地层层序的划分，对研究其构造演化和油气勘探有着重要的意义，对探讨太行山山前断层的发育特征也有一定的帮助。按照井、震结合的思路，利用最新的钻井和地震资料，并结合周缘的地质填图成果，建立了保定凹陷的地层系统；根据区域性不整合面的发育特征，对保定凹陷构造一地层层序进行了划分；利用平衡剖面技术，分析了保定凹陷的构造演化。研究发现，保定凹陷内发育了古近系孔店组底部和新近系馆陶组底部两个区域性角度不整合面，据此将保定凹陷在纵向上划分为3个构造层：基底构造层、断陷期构造层和拗陷期构造层。保定凹陷的形成演化经历了基底形成、古近纪断陷、渐新世末反转和新近纪一第四纪拗陷4个阶段，其中，古近纪断陷期又可以分为强烈断陷期、持续断陷期和断陷末期。

Baoding sag is located in the west of the Jizhong depression in the Bohai Bay Basin, separated with Taihang Mountains uplift by the Taihang Mountains piedmont fault. The dividing of tectono-stratigraphic sequences plays an important role in the determination of tectonic evolution stages and the exploration of petroleum resources in this area, and it can also provide significant clues to constrain the evolution of the Taihang Mountains piedmont fault. This paperdocuments the stratigraphic framework of the Baoding sag in using the latest seismic profiles, drilling data integrate with regional geological mapping results. The tectono-stratigraphic sequences are eonstrained by the regional unconformities, and the tectonic evolution of the study area is discussed based on the balanced section technique. Two regional unconformities including the bottom of the Paleogene Kongdian Formation and the bottom of the Neogene Guantao Formation are revealed, according to which three structural layers are recognized basement structural layer, rift structural layer, and depression structural layer. The tectonic evolution of the Baoding sag experienced basement formation period, Paleogene rift period, Late Oligocene inversion period, and Neogene-Quaternary depression period. The Paleogene rift period can be subdivided into three stages as well as strong rift stage, continuous rift stage and late rift stage.