Shidengzi Fm

The type section is located at Shidengzi, about 2 km west of Qiziqiao Town, Xiangxiang, Hunan. It was named by Tian Qijun and Wang Xiaoqing in 1932.

Synonym:

Huangjin Fm (in Guangxi)

Limestone and Claystone. Dominated by limestone intercalated with shale, obviously divided into three parts around Shaoyang of central Hunan. The Lower part is composed of dark-gray thick-bedded limestone, partly containing siliceous nodules, 60−100 m; the Middle part is of gray-black thin- to medium-bedded limestone and clayey limestone intercalated with marl and shale, containing abundant brachiopods, ~30 m thick; the Upper part consists of dark-gray and gray-black thick- and extremely thick-bedded limestone rich in corals and brachiopods, ~100 m thick.

In the Xinhua and Anhua areas near the Oldland in northern central Hunan, the Lower part of the formation is often intercalated with siltstone layers of meters to more than ten meters thick.

In southern Hunan, the division of three parts gradually dies out with decreasing clayey matter and increasing dolomitic matter. The formation there is composed of gray and dark-gray thick- and extremely thick-bedded limestone and dolomitic limestone intercalated with minor limy dolomite, usually containing siliceous nodules in the lower part, and intercalated with clayey limestone and marl or shale at the boundary between its top and the Ceshui Fm, 200−300 m in thickness.

The upper part of the formation contains abundant Corals, the Thysanophyllum-Kueichouphyllum sinense zone. Brachiopods are enriched in the middle and upper parts: the Marginoproductus-Ovatia zone for the middle and the Vitiliproductus-Pugilis zone for the upper. Foraminifers are also abundant, with the Dainella chomatic assemblage zone at the bottom, the Eostaffella bigemmicula-Pseudoendothyra ovata assemblage zone in the lower-middle, and the Mediocris medicris-Eodiscus explanatus assemblage zone in the upper part.

It is interpreted as platform neritic deposits