Abstract: The middle part of the Bohai Sea is called Bozhong Depression and situated in the east of the northern North China rifting basin(Bohai Bay Basin) of the Cenozoic time.Since Oligocene time,this area has subsided more than ten thousands meters and become a rich-hydrocarbon area in China.The major part of the Bozhong Depression is located in the northwest quadrant of the intersection area between the north-west trending Beijing-Ponglai fault zone and the north-north-east trending Tanlu fault zone.Meanwhile,it is also the pull-apart section of the extension-pull apart system in the eastern basin.There exists a north-west mantle swell striking in deep zone.The crust thickness ranges from 27 to 28 kilometers,and there is a complex and exclusive tectonic setting.Since Oligocene time,the middle Bohai Sea has experienced intensive subsidence,because of the superimposition of local tensional stresses produced by the left-lateral strike-slip on the Beijing- Ponglai fault zone,the right lateral strike-slip on the Yingkou-Weifang fault zone and the activity of the pull-apart structural system in the eastern basin as well as the affection of the uplift of the deep mantle.

Key words: middle Bohai Sea, Bozhong Depression, Cenozoic time, Bohai Bay Basin, extension-pull apart structural system, Beijing-Penglai fault zone, Oligocene, intensive subsidence

摘要： 渤海中部属于北华北新生代裂陷盆地(渤海湾盆地)东部的渤中坳陷,渐新世以来沉降深达10000余m,是我国少有的富生烃地区.渤中坳陷的主体部分位于北西向的北京—蓬莱和北北东向的郯庐2条区域性断裂带交汇区的西北象限,同时也是盆地东部伸展—拉分构造系统的拉分构造部位.深部存在北东向地幔隆起,地壳厚度为27～28km,构造背景复杂而独特.渐新世以来,北京—蓬莱断裂带左旋走滑、营口—潍坊断裂带右旋走滑和盆地东部伸展拉分构造系统活动各自产生的局部拉张应力作用的叠加,以及深部地幔上隆的联合作用,致使渤海中部自渐新世以来发生强烈沉降.

关键词: 渤海中部, 渤中坳陷, 新生代, 渤海湾盆地, 伸展拉分构造系统, 北京—蓬莱断裂带, 渐新世, 强烈沉陷