Sedimentary Facies Of The Paleogene In Western Segment Of Northern Margin Of Qaidam Basin

The western segment of northern margin of Qaidam Basin is one of first– order tectonic units in northern Qaidam Basin. Block the area has good prospects for hydrocarbon exploration. With the continuous progress in the field of petroleum exploration and production, the sedimentary facies analysis of the Paleogene in northern margin Qaidam Basin is of great significance for finding out lithologic oil– gas pools. Based on outcrop observation, core description, well logging and seismic data, facies mark of individual well and types of sedimentary facies are identified. The relationships between log facies and sedimentary facies have been established. The non- cores drills'sedimentary facies types and depositional system assemblages are discriminated by the method above. In the study area, the sedimentary facies are studied by using the corresponding relationship between the seismic facies and sedimentary facies and seismic reflections of each formation. The lithofacies change is analyzed in the isochronous stratigraphic frameworks and the sedimentary models were established.Based on the above researching, this paper has been gained some progresses:①Provenance analysis mainly includes com parison of debris com positions , heavy mineral assemblages, sedimentary facies , rare earth elements. The principle source of Erboliang-Lenghu zone of northwestern Qaidam Basin was derived from the Altyn Mountain. The principle source of Mahai- Nanbaxian zone of southeastern Qaidam Basin was derived from the Saishiteng Mountain.②five types of sedimentary facies are identified : alluvial fan facies, fan delta facies, braided stream facies, braided delta facies, lacustrine facies, of which the sedimentary characteristics are studied .③In the study area, the sedimentary facies are studied by using the corresponding relationship between the seismic facies and sedimentary facies and seismic reflections of each formation. The lithofacies change is analyzed in the isochronous stratigraphic frameworks and the sedimentary models were established. The formation units as the mapping unit have been selected. The lithofacies paleography map of northern margin in Qaidam Basin has been established.④the lithology and paleogeography in the Paleogene in western segment of northern margin in Qaidam Basin indicates that there mainly developed two sets of depositional system assemblages. Depositional environment attributes to alluvial fan- fan delta-lacustrine environment system in Erboliang-Lenghu zone of northwestern Qaidam Basin and alluvial fan– braided stream– braided delta– lacustrine environment system in Mahai- Nanbaxian zone of southeastern Qaidam Basin .