断陷湖盆古地貌恢复方法——以濮卫洼陷沙河街组三段中亚段为例

对断陷湖盆古地貌进行恢复,并探讨古地貌对沉积体系的控制作用。首先利用厚层盐岩作为重要等时对比标志,确定地貌恢复单元,再根据沉积物填平补齐的原理,并通过压实校正、重力载荷沉降校正和断层缝合,以构造沉降量来反映古地貌。恢复结果表明:沙三中沉积初期,濮卫洼陷呈东高西低、两洼夹一隆的构造格局,濮城断层上升盘受淡水补给影响,不发育蒸发岩,下降盘的深湖区,间歇性的洪水补给,浓缩形成巨厚膏盐层。沙三中沉积中期,濮卫次洼向北迁移,次洼内发育湖底扇沉积。沙三中沉积晚期,卫东断裂带与濮城断裂带活动加剧,形成南北两个洼陷带,濮城断裂下降盘具备蒸发岩沉积地貌。

The paleomorphology of the faulted basin is restored and the control of the paleomorphology on the sedimentary system is discussed.Firstly,thick-layered salt rocks are used as important isochronous comparison markers to determine the geomorphic restoration unit,and then the paleomorphology is reflected by the amount of tectonic subsidence according to the principle of sediment filling and patching,and through compaction correction,gravity load settlement correction and fault suture.The recovery results show that,at the early stage of deposition in the middle segment of the third member of Shahejie Formation,the Puwei Depression is a tectonic pattern of high in the east and low in the west,with two depressions sandwiching one ridge,and the rising disk of Pu Cheng Fault is influenced by freshwater recharge,and no evaporite is developed;the deep lake area of the falling disk,intermittently recharged by floods,concentrates to form a giant thick gypsum.In the middle stage of the deposition in the middle segment of the third member of Shahejie Formation,the Puwei sub-depression migrated to the north,and the sublacustrine fan deposition developed in the sub-depression.In the late stage of the deposition in the middle segment of the third member of Shahejie Formation,the activity of Weidong Fracture Belt and Pucheng Fracture Belt intensified,forming two depressional zones in the north and south,and the downthrown side of Pucheng Fracture has evaporite sedimentary landforms.