Chouniugou Fm

The type section lies on the north bank of the Chouniugou River, 35 km southwest of Wuwei, Gansu, within Tianzhu County. It was named by Yuan Fuli in 1925.

Claystone and Limestone. The Bottom consists of fine-grained conglomerate. Lower member is composed of littoral-neritic sediments, dominated by gray-black silty shale and siltstone, intercalated with thin-bedded limestone and thin coal seams; containing brachiopods, corals, fusulinids, spore-pollen, etc., 18−120 m thick. Upper member of sediments of neritic facies is dominated by thick-bedded limestone, intercalated with bioclastic limestone and sandy shale, 34−140 m thick.

In the eastern areas of Jingtai and Jingyuan, siliceous limestone occurs in the top, and siltstone increases in the lower part, yielding abundant fossil plants, 300 m thick. In the western Daqinggou of southern Gansu, limestone interbeds have reduced, with only 67 m exposed.

Corals Aulina rotiformis, Yuanophyllum kansuense, Kueichouphyllum sp., etc.; Brachiopods Gigantoproductus edelburgensis, Kansuella kansuensis, etc.; Fusulinid Eostaffella mosquensis zone. The Conodonts consist of two zones, i.e. the Gnathodus girtyi-G. bilineatus zone in the Lower part and the G. bilineatus-bollandensis zone in the Upper part. Spore-pollen (Gao Lianda, 1985) comprises 4 assemblage zones, which are ascending the Lycospora, Perotriletes-Schulzospora and Raistrickia-Triquitrites and Tripartites zones.

At places such as Hongshuibao, Jingtai, Gansu, Ammonoids are found, e.g. Goniatites cf. orientalis, Girtyoceras sp., Beyrichoceras sp., etc.

It is interpreted as littoral-neritic and neritic sediments.