Abstract:

A compound basin superimposed on Alxa Massif,Bayanhot Basin can be divided into 5 first units and 12 second units of tectonics that form 5 tectono-stratigraphic assemblies in the basin.Faults are the main factor in the formation and evolution of the basin.With the features of listric fault,Bayanwula Shan Fault controls the formation of the western depression belts.with its active intensity declining from north to south.Yinan Fault Belt controls the formation of Yihe depression,with the most active intensity in its middle Part.Chahan Fault is astrike-sliP fault with an obvious sinistral movement.The struetural style found in the basin includes imbrieated thrust zone，trapdoor strueture，drag fold，listric fault，rollover antieline，horst-graben strueture and the like.As the main oil-bearing bed in the basin，the Carboniferous system in the eastern and southerrn depression zones is provided with good trap conditions，thus possessing afavourable oil and gas potential.

Key words: Alxa Mssif, Trapdoor structure, Rollover anticline, Structure style, Tectono-stratigraphic assembly