Abstract:

The Bayanhot Basin is a Meso-Cenozoic faulted basin,which is superimposed on dis-tinct crystalline basement.With Chaxan fault as the boundary,the north of it is the stable Alxa Massif,and the south is the active Qilian folded belt.The structures within the basin are characterized by normal faults associated with rolling anticlines.A few thrusts and compressive folds are distributed mainly over thesouth part.The direction of the structures is NWW trending in the south part,NE in north-west and near SN in the east.In the Middle Proterozoic-Early Palaeozoic,the northwest Part of the basin wasrosen,the south part was the passive continental margin of Qilian trough,and east parta aulacogen.In the Late Palaeozoic,its south part was a foredeep and the east part wasa impactogen.The region was widely uplifted and magmations and faults occurred during the Permian-Triassic,marked the beginning of fragmentation of Alxa Massif.A lot of minor faulted basins separately occurred in the Jurassic.It became an unitary sedimentarybasin in the Early Cretaceous.At the end of Early Cretaceous,the basin uplifted again andthe activity diminished gradually.The Carboniferous source bed has so far been evidenced in the basin,discoveringmany oil-bearing formations in it.Therefore,the east and the south depressed zones withthick Carboniferous sediments are the most favourable region in oil and gas potential.