Baizitian Fm

It was named by The Compiling Groug of Sichuan Regional Stratigraphical Scale in 1974. The type section is located at Baizitian, Qinghe Town in Yanbian County, Sichuan Province. Coordinate: 101°20′59″E, 27°03′51″N. The subdivision of the Silurian strata in Baizitian section, Yanbian County, is contradictory to each other in recent studies (Jin et al., 2005; Wang Chengyuan et al., 2009; Wang Yi et al., 2016; Wang Guangxu et al., 2020). The Baizitian Fm is subdivided into 2 lithostratigraphic units, the Upper Baizitian Fm and the Lower Baizitian Fm (Wang Yi et al., 2016; Wang Guangxu et al., 2020). However, it is not suitable to keep these two names according to the rule for the official nomenclature of lithostratigraphic units as Wang Guangxu et al. (2020) pointed out. Consequently, the authors inclined to the opinion of Gu and Liu (1997) and Lin et al., (1998) to use the name Baizitian Fm for the Upper Baizitian Fm and the Lower Baizitian Fm.

Synonym: （稗子田组）

It is dominated by grey, dark grey argillaceous limestone, marl intercalated with carbonaceous limestone, carbonate breccia. The thickness is over 300 m at Baizitian, and gets thinner northeastwards and southwestwards.

It yields brachiopod Camarotoechia sp., trilobite Latiproetus cf. latilimbatus and Coronocephalus sp., corals Palaeofavosites sp., Favosites sp. and Mesofavosites sp., graptolite Monograptus flemingii，conodonts Plectospathodus extensus, Neoprioniodus excavatus, N. latidentatus，Pterospathognathus amorphognathoides, Carnidus carnicus, etc.