Baizhaoshan Fm

North Hubei. The Baizhaoshan Formation was named by Party of Regional Geological Survey, Hebei Bureau of Geology and Mineral Resources in 1982. The typical section is located at Baizhaoshan 3 km east of Anlu County, Hubei Province.

Synonym: （白兆山组）

In the typical area, the Baizhaoshan Fm is limestone and dolomite which is subdivided into two members. Lower member is composed of light gray, gray to dark gray limestone, dolomite and dolomite-limestone intercalations bearing siliceous bandings and nodules, and thin intercalations of chert. Upper member is composed of black gray to brown, medium-bedded chert with intercalations of dolomite and limestone, which bears siliceous nodules and bandings. The total thickness is 419 m, and from east to west and north, the lower member carbonate rock gradually thins to thins out: in Liulin of Suixian County with thickness of 196 m, in Dongqingmiao of Suixian only 6 m thick, and to the north of Dabeidian, 32 m thick. The chert in the upper member is an indicator horizon for boundary with Cambrian, whose outcrop is persistent but its thickness is unstable, in Liulin of Suixian it is 161 m, in Baizhaoshan it is only 20 m, in ShuangjianShan (Songhe) it is 42 m, and northward to Dabeidian-Shipansi it varies from 1 to 29 m.

The chert in Fuyinchong of Jingshan County was reported to have Praechrococus sp. and the Baizhaoshan Formation is referred to the late stage of the Sinian. The chert in the upper member is an indicator horizon for boundary with Cambrian.