According to lithologic characters, sedimentary structures, and biological  assemblages and their preserved states, Hirnantian can be mainly classified as tidal flat facies and neritic shelf facies. There are several subfacies and microfacies in this study area. The results show that the Hirnantian, in succession of the paleogeographic framework in the late Katian stage, also has the characteristics of the semi-restricted shallow sea. Regionally, it succeeds the environment of the neritic shelf facies in the late Katian stage in the north of the upper Yangtze and the most part of the middle Yangtze region, as well as the tidal flat facies among the middle Sichuan uplift, middle Guizhou uplift and Kangdian old land.