Caotangou Gr

The type section is at Caoliangyi in Danfeng County, Shaanxi. The Caotangou Gr was named by Shaanxi Party of Regional Geological Survey in 1967, and was published by Shaanxi Compiling Group for Regional Stratigraphic Scale (1978).

On the basis of the 1:200 000 scale geological survey in Xiangquan Sheet and the volcanic rock exposed in the vicinity of Caotangou, Shaanxi Regional Geological Survey (1967) renamed the Huang's and Chao's (1931) “Caoliangyi Coal Measures" the Caotangou Fm and the volcanic rock series underlying the coal measures the Caoliangyi Fm. Considering the fact that the Caoliangyi Coal Measures or Caoliangyi Fm has been widely accepted for long time, Shaanxi Compiling Group for Regional Stratigraphic Scale (1977) suggested that the previously defined “Caoliangyi Coal Measures" should be maintained, and renamed the underlying strata the Caotangou Gr (Shaanxi Bureau of Geology and Mineral Resources, 1989).

Synonym: (草滩沟群）

The group is composed of metamorphosed intermediate acid volcanic rock and normal sedimentary clastic rock intercalated with carbonate rock. In the type area, the group is 1000-2400 m thick.

The Caotangou Gr yields brachiopods Orthis cf. serica, O. cf. chinensis, Sinorthis cf. typica, Mimella cf. formosa and trilobite Basiliella sp. Corals Plasmoporella cf. granulosa, Heliolites aff. waicunensis, Amssia sp. and Reuschia sp. have been found from the crystalline limestone in the upper part of the Caotangou Gr at Liangdang.