Cenozoic structural evolution and prototype basin ofthe Great Qikou sag, the Bohai Bay Basin
Suo Yanhui1,2, Li Sanzhong1,2, Xu Liqing1,2, Dai Liming1,2, Liu Xin1,2, Guo Lingli1,2, Cao Huahua1,2, Дмитриенко Людмила Валерьевна1,2, Roya Nadiri1,2, Wang Pengcheng1,2, Zhou Lihong3, Lou Da3
1. Institute of Marine Geodynamics, College of Marine Geosciences, Ocean University of China, Qingdao, Shandong 266100;
2. Key Lab of Submarine Geosciences and Prospecting Technique, Ministry of Education, Qingdao, Shandong 266100;
3. Dagang Oilfield Company, CNPC, Tianjin 300280
The Great Qikou sag is located at the north-central of the Huanghua depression of the Bohai Bay Basin, being a Cenozoic basin superimposed on top of the Mesozoic basin. Based on a large number of 2D, 3D seismic profiles and drilling data, this paper focuses on the structural framework, characteristics of faults, and migration of depocenters and subsidence centers to analyze the tectonic evotion and prototype basin of the Great Qikou sag. Conlusions are as follows: 1)The Great Qikou sag includes four orders of tectonic units, resulting in the zonation in E-W direction and blocking in S-N direction in plane view and half-graben architecthure in profile. 2)The Great Qikou sag includes four orders of faults. The major faults are characterized by multiple-stage evolution and spatial migration in the sizes and activity, and the activity of major tectonic belts migrated from north to south. 3)The Cenozoic depocenters and subsidence centers were located at the eastern part of the Great Qikou sag, and the whole sag shows a trend of southern migration. 4)The structural evolution of the Great Qikou sag can be divided into four stages: Eocene propagating rifting, Early Oligocene pull-apart graben, Late Oligocene half-graben, and Miocene-Pleistocene thermal subsidence under dish-like bukling. Late Oligocene property is obvious during the rift stage. The Great Qikou sag is considered to be an "intraplate pull-apart basin" in such geological settings.