| Petroleum exploration has had a history of 50 years in the Qaidam Basin since 1954, whichmakes a framework-looking for oil in Jurassic and Tertiary strata in the western part of the basinand for gas in Quaternary sediments. Up to now, the western basin contains 90 percent of theproved reserves of the whole basin. Although much synthetical petroleum geology work has beendone on oil fields such as Youshashan, Shizigou and Huatugou in the west basin, the law of poolforming is still not fully understood, for strong structural movements in the region, which issurrounded by Altyn, Kunlun and Qilian Mountains, led to a complex distribution of reservoirrocks. So detailed studies on allocation between sedimentation and paleostructure in the mainaccumulation time and forecasting perspective plays, by way of many subjects such as basin andpetroleum system analysis, and sequence stratigraphy, will become more and more important inlowering the risk, and increasing the efficiency in the petroleum exploration and economicalbenefit by reducing risks. And they will give proves for selecting prospective plays. In this study we focus on Cenozoic formations, which are in stratigraphic order: PaleoceneLulehe Formation, early Eocene lower part of the Lower Ganchaigou Formation, middle Eoceneupper part of Lower Ganchaigou Formation, late Eocene-Oligocene Upper Ganchaigou Formation,early Miocene Lower Youshashan Formation, late Miocene Upper Youshashan Formation,Pliocene Shizigou Formation and Pleistocene Qigequan Formation. The paper addressespaleocurrent distribution, sedimentary paleogeomorphology and distribution of sedimentary faciesin different stages, which can likewise be separated into (shallow water) fan delta, alluvial fan,diluvial fan, coastal and shallow lake, half-deep lake, alluvial plain and coastal sedimentary facies. By reason of the complex structures in the Qaidam Basin it is not enough to converse the basin'sevolution history only by structure explanation. The research on paleostructures, geometric shapeof sediment filling and distribution of lithofacies in different stages may be a good approach torecognize processes and the dynamics during evolution. The characteristics of the western basinsedimentary response reveal that the region had undergone many different-dynamic crustmovements from the stage of Yanshan to the Himalayan stage, which can be divided into fourstages: 1) strike-slip and extensional rifting during Mesozoic, 2) extensional rifting-depressionduring Paleocene-Miocene, 3) strike-slip and extensional depression in late Eocene-Pleistoceneand 4) extrusion, deflection and strike-slip from the end of Pleistocene on. The Qaidam Basin wentthrough the above four basin-stages, and represent today a complex distorted basin. By analyzing four regional paleostructures which formed before the deposition of the lateEocene-Oligocene Upper Ganchaigou Formation, early Miocene Lower Youshashan Formation,late Miocene Upper Youshashan Formation and late Quaternary formation, we know that the widearea whose "axial cord" is located in Shizigou-Third Hongsanhan, which is concordantwith thedevelopment of the depression center since Paleocene, indicating large-scale and strongnorth-northeast shape changes such as extruding and deflecting folds, and thrust faults. However,the main dynamic mechanisms of the basin's evolution were extensional rifting-depression anddepression. The western basin displays many accumulation times. Distinct source rocks show inconsistentcharacteristics in extent and time of thermal degradation between the different structural units, dueto the differences of the conditions during deposition, and tectonic subsidence. In front of Altynand Kunlun Mountains source rock maturation occurred late, compared with eastern and westernbasin parts, such as the Third Hongsanhan. The earliest maturation stage of source rock in thewestern Qaidam Basin is believed to be late Eocene, while for the Third Hongsanhan's, it sh...
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