Sedimentary facies of the Paleogene Ganchaigou Formation in the North-West Qaidam Basin, Western China

Le Li, Ping Guan, Wentao Zhang, Binbin Du, and Guoyuan He

The Qaidam Basin in the western China is a major Meso-Cenozoic petroleum basin. This paper deals with the recovery of the sedimentary evolution history and distribution of the Paleogene Ganchaigou Formation in the North-West Qaidam basin on the basis of analysis of single-well and multi-crosswell profile sedimentary facies analysis. The result shows that period of E1+2 were the occurrence of Lake Basin stage. Most of the region was braided-river and over-bank deposit. There was a small-scale orogeny in early E31, and the deposition system can be summarized as alluvial fan, braided river delta and shore-shallow lacus sedimentary system. After the orogeny, the lake area began to expand. During period of E32, the climate turned into semi-arid from arid. Freshwater recharge capacity increased, the lake expanded and the water level rose. The lake basin developed into its flourishing period. Fluvial facies and delta facies retrograded to the northeast. The area of lacustrine sedimentation turned into its maximum in period of E32, the lake area further expanded and the depth of water further increased. The deposition center was located in the Nanyishan and Xiaoliangshan region.