反向断阶构造样式与砂质沉积体发育

孤南洼陷是一个复合的半地堑盆地 ,洼陷斜坡发育由断层和断块构成的断阶构造样式 ,其中一种为反断阶。反断阶的发育使得盆地斜坡的沉积地形复杂化 ,因此发育其上的砂质沉积体具有特殊的分布型式 ,包括展布方向、几何形态和水流特征。孤南凸起东南斜坡的反向断阶是由一正断层和倾向相反的斜坡构成。斜坡总体向盆内倾斜 ,但在断层处形成一个次级隆起。沙河街组二段的砂体是在这样的复合地形上沉积并赋存下来。在平面上该砂体一方面沿沉积斜坡方向延伸至断层 ,一方面沿断层走向延伸或越过断层 ,呈不规则的丁字形。砂体在越过孤南洼陷与孤岛凸起的分界断层后在远端发散 ,形成扇体。

THE STRUCTURAL STYLE OF ANTITHETIC FAULT TERRACE AND THE DEVELOPMENT OF SAND BODIES

Gunan trough is a complex half graben basin, where the structural styles of fault terrace developed on the slops, one of them is antithetic fault terrace .The development of this kind of fault terrace made the sedimentary surface on the slop complicated. So the sand sediments depositing on the fault terrace had a special pattern of distribution, including orientation, geometry and water flow.The antithetic fault terrace developed on the southeast slop of Gunan uplift is composed of a normal fault and the slop with an opposite trend. The slop tilted basinward and a sub-uplift occurred on the footwall of the fault. The sand bodies of Mum.2, Shahejie formation deposited and reserved on this complex topographic surface. The sand bodies extended to the fault on the slop and turn direction along the fault toward basin or crossed the fault, showing an irregular "J" type. The sand bodies scattered to form fans at far end when they crossed the boundary faults between Gunan trough and Gudao uplift.