东营凹陷断裂活动特征及其对沉积的控制作用

应用断层落差法,对东营凹陷沙河街—东营期的断裂活动特征进行了研究.研究表明:东营凹陷古近纪在近南北向的伸展方向上,断裂活动强弱交替,在沙三—沙二早期,东营凹陷断层活动强烈,沙二晚期—东营期断层活动明显减弱.东营凹陷的断层在平面上、剖面上有多种不同的几何形态,组成了半地堑、半地垒和地堑—地垒多种形式的断块体,其组合的分布使整个东营凹陷具有南北分区块断的构造特征;断裂活动时空分布具有不均一性,在北西—南东向和南北向的双向伸展作用下,东营凹陷的断裂活动在空间上具有分段性特点.东营凹陷的断裂活动不仅控制着构造演化,而且控制着凹陷内的沉积演化.同一时刻,同一条断层,断层落差较大的中央部位发育了扇三角洲,而两翼落差较小的部位发育有湖相泥岩沉积;一级断层控制了凹陷沉积体系的地层厚度,二级断层控制了扇体的类型及规模,而三级断层控制了砂体的分布.

Characteristics of the fault activities in Dongying Depression and their controling effects on sediment

The characteristics of the fault activities of Dongying Depression in Shahejie—Dongying period are researched by using fault drop method.The research results show that the strong and weak fault activities are alternate in the extension direction of S—N during the Paleogene,the fault activities are strong in Es_3 and early Es_2 periods,and they obviously weaken in later Es_2 and Ed periods.The faults have manifold geometrical forms in plane and profile,which forms manifold faulted blocks—— half graben,half horst and graben-horst faults,and the distribution of the faulted blocks makes Dongying Depression segmented into north and south blocks.The distributions of the fault activities in space and time are unbalanced.Under the effects of the double-directional extension in NW—SE and S—N,the fault activities present sections in space.The fault activities control not only the structural evolution,but also the depositional evolution of Dongying Depression.Fan delta develops in the central part of a fault where there is greater fault drop,and limnic mudstone develops in its two limbs where there is less fault drop.The first-order faults control the stratum thickness of depositional system,the second-order faults control the types and scales of fan bodies,and the third-order faults control the distribution of sand bodies.