Formation and segmentation of the East Rise,Liaodong Bay Depression controlled by the Yingkou-Weifang fault zone:Evidence from physical modeling and structural geometry
Cao Zhongxiang1, Ren Fenglou2, Song Guoqi1, Qi Jiafu3
1. Exploration Item Management Department, Shengli Oilfield Branch Company, China Petroleum and Chemical Corp., Dongying, Shandong 257015; 2. Instititute of Geological Science, Shengli Oilfield Branch Company, China Petroleum and Chemical Corp., Dongying, Shandong 257015; 3. Key Laboratory for Hydrocarbon Accumulation Mechanism, Ministry of Education, China University of Petroleum. Beijing 102249
The Cenozoic development of the Liaodong Bay Depression, located in northern part of the Bohai Bay Basin, was controlled by the Yingkou-Weifang fault zone. The East Rise, its suborder tectonic unit, was sandwiched in between two branch faults. Based on structural interpretation of several seismic profiles across the Liaodong Bay Depression, the structural geometry characters of the faults on both sides of the East Rise were systematically analysed. The East Rise of Liaodong Bay Depression might come into being on a lower uplift during Oligocene (sedimentary period of the Dongying Formation), resulted from dextral strike-slipping of the Yingkou-Weifang fault zone.The rise could be divided into two segments, with the seismic lines of Lz205 and Lz185 being a boundary. Each segment showed a change, with their northward stretching, from dextral transextension to shearing, then became a dextral transcompression. The structural segmentation should be caused by varied orientations of the basement fault (NE-striking) and the induced Cenozoic fault (NNE-striking). In the southern segment, the both of faults converged near the seismic line Lz151, where the transextention fault to the south of the line changed to shearing then became a transcompression fault. In the southern terminal of the northern segment, the both of faults diverged again and the dextral transextention dominated again. At the seismic line Lz255, the NE-striking fault zigzaged, and corespondingly, the fault changed to strike-slipping and then became a transcompression fault. Our physical modeling experiments repeated the changing of dextral transextention-shearing-dextral transcompression, which confirmed that the mechanical variation and structural segmentation should be resulted from variation of local stress fields induced by dextral strike-slipping of the Yingkou-Weifang fault zone since Oligocene.
Cao Zhongxiang,Ren Fenglou,Song Guoqi et al. Formation and segmentation of the East Rise,Liaodong Bay Depression controlled by the Yingkou-Weifang fault zone:Evidence from physical modeling and structural geometry[J]. Chinese Journal of Geology, 2008, (2): 238-250.