渤海盆地新生代构造演化特征

在渤海盆地8个主要凹陷各选取一口井,对每口井构造沉降史特征进行分析,结果表明渤海盆地的构造沉降特征各凹陷不统一,南部和北部先沉降,再逐渐向中部迁移,最后以中部沉降为主,沉降中心明显由周缘向盆地中心迁移,反映构造活动的阶段性和地区差异性。在辽东湾选取了一条地质剖面对其做平衡剖面分析,并结合构造沉降史分析,表明渤海盆地的新生代构造演化分为以下3个阶段:a.断陷期,孔店组—沙四段沉积时期为断陷早期,沙三段沉积时期为强烈断陷期;b.断拗期,沙二段—沙一段沉积时期为断拗早期,东三段—东二段沉积时期为强烈断拗期;c.坳陷期(东一段沉积时期—第四纪)。

Cenozoic Geotectonic Evolution of the Bohai Basin

Choosing one well separately in eight main sags of the Bohai basin and analysing the subsidence history of each well, we come to a conclusion that the subsidence characteristics of different sags were different.The southern part and the northern part of the basin subsided first,and the central part subsided at a later time.The subsidence center migrated from outside towards the basin center,which reflects the difference of tectonics in different parts of the basin.We made a balanced section analysis for the Liaodong Bay.Combining the subsidence history,we divided its Cenozoic tectonic history into three stages:(a)Rift stage. The time from the Kongdian Formation to the fourth member of the Shahejie Formation is the early rift stage,and the time of the third member of Shahejie Formation is the intensive rift stage;(b)Fault depression stage.The time from the second member of the Shahejie Formation to the first member of the Shahejie Formation is the early fault depression stage,and the period from the third member of the Dongying Formation to the second member of the Dongying Formation is the intensive fault depression stage;(c) Depression stage.This stage lasted from the first member of the Dongying Formation to the Quaternary.