渤海湾盆地东营凹陷中央背斜带构造特征和演化机理

渤海湾盆地东营凹陷沙四段盐膏层和沙三段超压泥岩层等塑性物质的存在,为弹性基础悬臂梁理论在该区的应用提供了必要的物质基础.自沙四段沉积晚期开始,东营凹陷东段的受力以及变形状态就类似于以下伏盐膏层为弹性基础,以南部广饶凸起为固定端,以北部陈南断层为自由端的弹性基础悬臂梁,在自身重力以及上覆沉积物载荷不断增大的情况下,自由端的沉降幅度逐渐增大,使得盆地整体呈箕状产出,在这个沉降过程中,塑性物质不断流动聚集,对上覆地层造成拱升,从而形成中央背斜带.此后悬臂梁又一分为二,单独作用,继续推动着整个凹陷的演化进程.

Tectonic feature and evolution mechanism of central anticline belt of Dongying Sag, Bohai Bay Basin

The present of plastic substances such as evaporate beds in the 4th member (Es4) of the Shahejie Formation and the over-pressured mudstone layers in the 3rd member (Es3) of the Shahejie Formation in the Dongying Sag provides the necessary material foundation for the application of Cantilever theory in this area.Since the late Es4 period,the loading state in the east of the Dongying Sag as well as its deformation resembled a plastically-founded cantilever which was based on the underlying cream salt layer,fixed on the southern Guangrao Uplift and free on the northern Chennan Fault.With its own gravity and the growing load of overburden sediments,the amplitude of sinking in the free end was gradually increasing,making the basin look like a dustpan.During the sinking,plastic substances kept flowing and aggregating,forcing the overburden layer to arch and finally forming the central anticline belt.Then the cantilever split into two parts which performed individually and continued to drive the evolution of the Dongying Sag.