文留盐构造成因与掩埋机制

STRUCTURAL EVOLUTION OF THE WENLIU SALT DIAPIR AND GRABEN,BOHAI BAY

文留盐构造位于东濮坳陷中央隆起带上，是中原油田重要油气圈闭构造之一。该构造形成于早第三纪沙三段早期，其演化完全受区域拉张、局部构造及同构造沉积的控制。在厚皮拉张过程中，塑性流动盐层使上覆层与基底的形变发生部分拆离，形成文留构造的三层式结构：下部基底地垒，中部盐核及上覆层强制褶皱背斜与拱顶地堑。区域拉张形成中部隆起垒块，同构造沉积将盐体从两凹挤向中隆，使早期的盐枕演化成次动盐刺穿。晚第三纪时，区域拉张减弱，盐构造运动随之减弱，文留构造被上第三系和第四系沉积物深埋。尺度物理模拟采用干石英砂及硅树脂胶为实验材料，模拟了文留构造的动力演化过程。

The Wenliu salt structure is localized above the central uplift in the northeast part of the Dongpu depression,Bohai Bay basin.The structure comprises downwards a simple crestal graben,a thickened salt core,and a basement horst.The structure was formed during the early of sha 3,stage of Eogene thick skinned extension.At an early stage,the salt layer partially decoupled deformation above and below the salt.The overburden formed forced fold that was cored with salt pillow above the central basement horst block.A graben formed at the crest of the forced anticline due to local arching.By the combination of regional extension and local stretching,the crestal graben widened and triggered reactive diapirism.Synkinematic sediments in the flank depressions caused salt to flow upward to the central basement uplift,which enhanced the rise of the Wenliu reactive salt diapir.As regional extension decreased,the reactive diapir ceased to rise and was buried by the Neogene and Quaternary sediments. We used scaled physical models of basement involved salt tectonics and salt dissolution to simulate the development of the Wenliu structure.The experiments reproduced the dynamic evolution of the Wenliu structure by regional,thick skinned extension.Conversely,salt dissolution had negligible influence on the formation of the simple Wenliu graben.