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.