Neogene sedimentary facies and palaeogeography of western Qaidam Basin, Qinghai

In the light of lithology, sedimentary structures and textures and palaeontology, the Neogene sedimentary facies in western Qaidam Basin, Qinghai consist of fan delta, fluvial-flood plain, littoral lake, shallow lake and bathyal lake facies. From the central Mangnai and Dafengshan to the basin margins, there develop the bathyal lake, shallow lake and littoral lake facies. The fan delta and fluvial-flood plain facies appear in the foreland of the Kunlun and Altun Mountains. The palaeotopography displayed the patterns of being higher in the western and southern parts and lower in the eastern and northern parts of the Basin. The palaeoclimates were hot and dry. The principal sources of detritus lay to the Kunlun and Altun Mountains. The Lower Youshashan Formation is believed to contain good source rocks. The reservoir rocks consist of porosity clastic reservoirs and fractured reservoirs.