Sedimentary Setting of Mesozoic and Its Petroleum Geologic Features in Western Tarim Basin

The geophysical information and surface geologic data from Kashi sag in Tarim basin are comprehensively analyzed.The study shows that several sedimentary centers appear in Mesozoic of this area,characterized by that the thickness in the west is bigger than that in the east and pinch-out toward the east.There exist two sedimentary systems in Jurassic: one is the fault basin within Talas-Ferghana fracture belt;the other is the piedmont depressions in South Tianshan and West Kunlun mountains,with distinct differences between them in lithology.Accordingly,the source rocks in the two systems produce two petroleum systems,and the petroleum geologic feature of Mesozoic in Kashi sag is obviously different with Kuqa depression in the east and Afghanistan-Tajikistan basin in the west.It is believed that the reason for such differences is that the sedimentary settings in Mesozoic era are different among them.