By studying the Mengshan section in Pujiang County, Zhejiang Province, this paper established two unit-stratotypes: Mengshan Formation and Chentangwu Formation. These two formations can be united into Pingshui Group, which is a former used lithostratigraphic unit and has been revised the meanings in this research. The lower part of Pingshui Group is Mengshan Formation (spilite-keratophyre formation) and the upper is Chentangwu Formation (marine facies sand-mudstone formation). Pingshui Group, representing the oldest basement in northwest Zhejiang Province, is conformably overlain by Shuangxiwu Group. Through study and argumentation of microflora and isotope age in the stratotype section, the authors proposed that the geologic age of Pingshui Group belongs to the Meso-Neoproterozoic.
