Introduction
Qaidam basin, located in Qinghai Province, is on the northern margin of Qinghai-Tibet Plateau. It has been known as one of the three major interior basins besides Tarim Basin and Junggar Basin. Qaidam Basin is a component of the Xiyu Plate, surrounded by the mountain ranges and discordogenic faults of Qilian, Kunlun and Altun. Qaidam Basin belongs to Tarim-Sino Korea Plate. With neighboring plates and crustal blocks, it experienced continental dispersion, ocean crust subduction, arc-arc or arc-continent collision accretion during Palaeozoic Era, and within-plate deformational supraposition in Meso-cenozoic. On the basis of partial fault subsidence in Mesozoic, the Cenozoic sedimentary structure evolvement experienced fault sag transition, fault sag and inverted fold. Previous research has made great contribution in exploring and researching the sedimentary facies of Tertiary in North-West Qaidam Basin (Dang, et al., 2004; Jin, et al., 2002; Yang, et al., 2003; Wu, et al., 2003; Gao, et al., 2003; Wang, et al., 2002). However, there were relatively few discussions about the classification of the sedimentary microfacies and subfacies (Tian, 1996; Huang, et al., 1993; Liu, et al., 2009; Li, et al., 2009). This paper aimed at the determination of plane distribution of facies and sedimentary evolution model.