SALT DIAPIRISM AND FAULTING OF THE CENTRAL UPLIFT BELT IN THE DONGYING SAG, BOHAI BAY BASIN, NORTH CHINA
Yu Jianguo1, Li Sanzhong2, Wang Jinduo1, Wang Xinhong3, Lu Shenqiang1
1. Institute of Geophysic Exploration, Shengli Oilfield Ltd. Corp., China Petroleum & Chemical Corp., Dongying, Shandong 257022; 2. College of Marine Geosciences, Ocean University of China, Qingdao, Shandong 266003; 3. Geophysic Exploration Company, Management Bureau of Shengli Oilfield, China Petroleum & Chemical Corp., Dongying, Shandong 257100
A lot of growth faults developed in the Dongying Sag of the Jiyang Depression, Bohai Bay Basin, North China. These normal faults made up some flower-like groups, and the grabens occurred in their hanging walls of the major faults accompanying with reverse dragging. On the other hand, the central uplift belt, an important structural unit in the Dongying Sag, was divided into a series of small blocks by these faults. In this paper, these faults and the related small blocks were divided into three main structural belts, namely the Xinzhen, the Dongying and the Haojia-Xianhezhuang(the Hao-Xian for short)structural belts. Our study showed that these complicate blocks and “negative flower-like” fault groups in the central uplift belt resulted from regional NNW—SSE extension accompanying with local salt diapirism as well as related reverse dragging, rather than strike-slip faulting. Based on the diapirism strength, diapirs in these areas could be divided into two types: lower uplift and blind piering structure. Diapirism started at sedimentary period of the 3rd Member of Shahejie Formation, and terminated at sedimentary period of the Guangtao Formation. Diapir was mainly composed of some salts, and minor soft mudstone or other plaster sediments.