In this paper, it is shown that the “Jiangkou Formation” includes the redefined Jiangkou Group and the interglacial Datangpo Formation. The Jiangkou Group in turn includes the Chang’an Formation and Fulu formations, the latter consisting of the Liangjiehe and Gucheng members. However, the Nanhuan stratigraphy of this area is characterized by several interesting features. First, contrary to the general belief that the Gucheng Member is widely distributed, this unit is missing in many places. Second, unlike elsewhere in South China where the Datangpo Formation consists mostly of black or carbonaceous shale and manganese-rich deposits (e.g., in Hunan, Guizhou, and Northern Guangxi provinces), this unit in the study area is composed of grey-green slate, with little carbonaceous or manganese-bearing shale, highlighting the unusual sedimentary environment of the study area.