Silurian System in the Three Gorges Areas of Hubei

This is the Silurian System in the Three Gorges areas of Hubei. This system is located in the Dazhongba area of Yichang City, Hubei Province, and it includes two stage stratotype sections, namely, the ‘Longmaxi Stage’ and the ‘Dazhong Stage’ at the base of the Silurian. The ‘Longmaxi Stage’ section is mainly composed of black graptolitic shale that is rich in graptolite fossils, and the first appearance of Akidograpus ascensus is considered the standard indicator. There are four graptolite zones, which are equivalent to the ‘Rhuddanian Stage’ on the International Stratigraphic Chart. The lower part of the ‘Dazhong Stage’ section is composed of black graptolitic shale that gradually transitions into a thin layer of yellowish green shale in the upper part, which is signified by the first appearance of the graptolite Demirastrites tragulatus as a standard indicator and is equivalent to the ‘Aeroian Stage’ on the International Stratigraphic Chart.