Subdivision of the Nanhuan System in Guizhou-Hu'nan-Guangxi border area based on the well-reserved Nanhuan System section in Lijiapo, Congjiang County, Guizhou Province

Previous researchers failed to specify the stratotype section of 'Nanhuan System', and its internal division still has many divergences. China Geological Survey began to look for Nanhuan stratotype boundary system through 1:50000 regional geological survey. Through this work, the authors found a section in Lijiapo area, Congjiang County, Guizhou Province, which is characterized by well-reserved sequence, sedimentary succession, huge sedimentary thickness, clear layer and clear top to bottom line. Based on investigation of the section, field work in this aspect conducted in Guizhou-Hu'nan-Guangxi border area, northwestern Hu'nan and eastern Sanxia and other research results obtained recent years, and guided by complete development process of Nanhuan Great Ice Age, the authors have divided tentatively the interior of the Nanhuan System. According to sedimentary record of Lijiapo Nanhuan section, the Nanhuan great ice age is divided upward into Chang'an ice age, Fulu interglacial age and Nantuo ice age. The Nanhuan System can be further divided into three series:lower series corresponding to Chang'an ice age sedimentary sequence, middle series corresponding to Fulu ice age sedimentary sequence, and upper series corresponding to the Nantuo ice age sedimentary sequence. The results obtained by the authors have provided a more logical plan for dividing the internal Nanhuan System.