An analysis of the Cambrian sedimentary environment in southern Hunan Province

The Cambrian strata in southern Hunan can be divided from bottom to top into Xiangnan Formation, Chayuantou Formation and Xiaozijing Formation. The rock types are mainly clastic rock and subordinately carbonate rock and siliceous rock, in which sandstone and mudstone(shale)often form typical flysch rhythms. Based on a comprehensive study of such facies indicators such as lithologic character, palaeobiologic fossils and sedimentary structure, the authors hold that the Cambrian sedimentary environment of the study area was a deep-water slope to basin environment. The sedimentary environment evolution was analyzed and the sedimentary model was set up. The area experienced three transgression events during Cambrian. The first transgression began in the Jinning stage and ended in the Nangao stage. The second transgression began in the Duyun stage and ended in the Wangcun stage. The third transgression began in the Guzhang stage and lasted until the Niuchehe Age.