北山-阿拉善地区侏罗-白垩纪盆地的叠合演化

Evolution of superposed Jurassic and Cretaceous basins in Beishan-Alxa area

李明杰 郑孟林 曹春潮 张军勇

Li Mingjie Zheng Menglin Cao Chunchao Zhang Junyong

北山阿拉善地区的侏罗纪盆地受近东西向构造控制,划分为阿拉善沉积区和蒙古造山带沉积区。蒙古造山带内形成的侏罗纪盆地可划分为黑鹰山-额济纳旗沉积带,公婆泉-中口子-苏红图(尚丹)沉积带。蒙古造山带内发育的侏罗纪盆地较阿拉善地块内发育的盆地面积小,分布零星,后期改造强烈。早白垩世盆地受北东向构造控制,具有箕状或不对称断陷结构,为北东向展布的相互独立的断陷湖盆,也可分为阿拉善和蒙古造山带两大沉积区,在造山带内发育的盆地发育了一套优质烃源岩,而在阿拉善地块内发育的白垩纪盆地为一套杂色碎屑岩沉积,缺少烃源岩。白垩纪盆地与侏罗纪盆地为大角度叠合,存在交错叠合和披盖叠合两种型式,披盖叠合型式有利于早期盆地烃源岩的埋藏、成熟,是有利的勘探区。

The Jurassic basins in Beishan-Alxa area have been controlled by near EW-trending faults and can be divided into Alxa and Mongolia orogenic belt two sedimentary provinces.The Jurassic basins in Mongolia orogenic belt can be subdivided into Heiyingshan-Ejinaqi and Gongpoquan-Zhongkouzi-Suhongtu (Shangdan) sedimentary zones.They have smaller areas than those in Alxa sedimentary province and have experienced stronger epigenetic deformation.The Early Cretaceous basins,controlled by NE-trending faults,are faulted lake basins separately distributed in NE direction in the shape of half graben or asymmetric faulted basins. They can also be divided into two sedimentary provinces,Alaxa and Mongolia orogenic belt.A set of very good source rocks have been developed in Mongolia orogenic belt,and a set of clastic rocks rather than source rocks have been developed in Cretaceous basins in Alaxa block. The Jurassic and Cretaceous basins superpose in high angles. There exists two superposition patterns,cross superposition and drape superposition,and the latter is favorable for the early burial and maturation of source rocks in the basin.Therefore it is a favorable exploration area.

10.11743/ogg20040110