Abstract:

The east-west trending overthrust belt along the southern margin of Jiuxi Basin,Gansu Province,extends 100km long and 10km wide.This belt is composed of the fault on the south margin of the basin and the one on the north side of Laojunmiao anticline.These listric faults dip to south,and their dip angles are usually ranging 20-60?.Anticlines such as Shiyougou,Laojun-miao,Yaerxia,and Qingcaowan are all on the upthrown wall of the fault on the north side of Laojunmiao anticline belt.It has been proved that commer-cial oil flows have been discovered in the above mentioned first three anticlines.The trap type of these anticlines are considered to be nappe-related drag folds and intermediat fault blocks.Qingxi depression on the north side of the over-thrust belt is the largest depression in oil generation within Jiuxi Basin.InUpper Jurassic-Lower Cretaceous,there are favourable source rocks.It is pre-dicted that new subtle oil pools could be discovered on the downthrown wallof the overthrust.