Jiusi Fm

The type section is located at Jiusi, 12 km east of Xiguan (formerly Datang), Pingtang County, Guizhou. It was named by Ding Wenjiang in 1931.

Limestone. The formation can be divided into 3 members: Lower (Datian Member), dominated by limestone intercalated with shale and marl, with thickness varying greatly, reaching 257 m at the Xiangbai Timber Yard, and only 76 m at Bianjie Street of Huishui. Middle (Yashui Member), composed of dark-gray and gray-black moderately thick-bedded compact micrites, intercalated with marl, chert limestone and minor shale, 80−150 m thick. Upper (Liuzhai Member), light-gray moderately to thick-bedded fine-grained sandstone, intercalated with gray-black shale and moderately thick-bedded limestone and marl, reaching the thickest 80 m at Xiguan, thinning gradually toward the surroundings, and occurring intermittently as lenses in Guiyang et al. In areas where the Liuzhai Member disappears, the formation turns into gray-black moderately thick-bedded micrite intercalated with marl and minor shale, and cannot be divided into members. The thickness is generally several to tens of meters, rarely exceeding a hundred meters.

The Lower part yields Corals Thysanophylloides chui, Donophyllum (Polygonalia) carbonica, Michelinia datangensis, Siphonodendron curvatum, Kueichouphyllum sp., (minor) Syringopora sp., etc.; Brachiopods Pugilis hunanensis, Vitiliproductus groberi, Delepinea comaides, D. transversa, D. sinensis, Megachonetes sp., etc. The Middle and Upper parts yield Corals Kueichouphyllum sinense, K. heishihkuanense, Kusbassophyllum sp., Neoclisiophyllum sp., Heterocaninia tholusitabulata, Diphyphyllum convexum and Siphonodendron sp.; Brachiopods Delepinea extensa, D. subcarinata, Balakhonia yashuiensis, B. convexa, etc.

It is interpreted as an open sea-platform facies