鄂尔多斯盆地三叠系延长组地震层序地层研究

Seismic sequence of Triassic Yanchang Formation in Ordos Basin

依据Cross的高分辨率层序地层学理论,将鄂尔多斯盆地三叠系延长组地层划分为1个二级层序,5个三级层序。二级层序的顶界面为侏罗系与三叠系之间的不整合面,底界面为延长组的底,最大湖泛面为盆地内部广泛发育的张家滩页岩。在二级层序内部,依据沉积间断面、湖泛面、冲刷面、沉积转换面及岩性转换面,可识别出三级层序,并总结了层序界面在地震剖面上的特征,依此特征对地震大剖面进行了层序解释,分析了延长组地层纵向上的演化规律。

According to Cross theory on high resolution sequence stratigraphy, Triassic Yanchang Formation is divided into one second-order sequence and five third-order sequences. The top boundary of the second-order sequence is the unconformity between Jurassic and Triassic, the bottom boundary is the bottom of Yanchang Formation, and the maximum flooding surface is Zhangjiatan shale which distributes broadly in the basin. The third-order sequences can be identified by the surface of interrupted deposition, flooding surface, scour surface, sedimentary transformation surface and lithology transformation surface. The characteristics of sequence boundary surface in seismic profile are concluded. According to these characteristics, the seismic profile is interpreted and the evolution of Yanchang Formation in vertical direction is analyzed.