新近纪鄂尔多斯盆地东西部的构造反转及其意义

对鄂尔多斯盆地东、西部中生界顶面上、下分布地层的综合分析表明,鄂尔多斯盆地东部中生界之上接受的新生代最老的地层为新近纪的红粘土,这种红粘土分布广泛,厚度较大,自西向东分别覆盖于下白垩统、中侏罗统安定组及直罗组、下-中侏罗统延安组和上三叠统延长组之上。由此推断,盆地东部由晚侏罗世以来的持续隆起转变为坳陷接受沉积的时间为新近纪红粘土开始沉积的时间。由其底部的磁性地层测年可知,其反转时间约为距今8Ma。而裂变径迹测试分析资料表明,盆地西部在距今8Ma左右发生了逆冲抬升,由中生代以来的持续坳陷反转为逆冲抬升并遭受剥蚀。故鄂尔多斯盆地东、西部在新近纪均发生了构造反转。此次的构造反转对盆地内油、气流体矿产产生了重要的影响。

Structural reverse and its significance to oil and gas in the east and west parts of Ordos Basin in the Neogene

The analysis on the strata distribution upper and under the top surface of the Mesozoic showed that the Neogene red clay was widely distributed in the oldest Cenozoic strata deposited in the east part of Ordos Basin.The red clay had a great thickness and overlapped on the Lower Cretaceous,Anding Formation and Zhiluo Formation in the Middle Jurassic,Early-Mid Jurassic Yan'an Formation and Late Triassic Yanchang Formation,respectively.The magnetostratigraphy dating showed that there existed a reverse event in the east part of Ordos Basin at about 8 million years before present,and the east part of Ordos Basin turned from the continuous uplift to thrust in the deposition stage of red clay.The fission track dating data indicated that the west part of Ordos Basin also experienced a structural uplift.It is supposed that the reverse time is also about 8 million years before present.The structural reverse times of the east and west parts of the basin in the Neogene are synchronous,which has a great significance to the fluid deposits of oil and gas in Ordos Basin.