Baizuo Fm

The type section is located at Baizuo, Pingfa (Yunwu), 43 km south of Guiding, Guizhou Province. It was named by Yang Senwu and Jiang Chaoyang in their manuscript in 1963.

Dolomite. The lower and middle parts are composed of dolomite and dolomitic limestone; the upper part, of limestone (“three-layered”) or limestone intercalated with dolomite (“five-layered”). The intercalated dolomite is regionally unstable, while the upper and lower two suites of dolomite are relatively stable. However, dolomites of this formation are epigenetic dolomites, so that they are mainly stratiform and bedded, but some are lenticular and lumpy, or dolomites intercalated with limestone lenses. In the sections such as Baijin of Huishui, Baizuo of Guiding, Dewu of Shuicheng, Bainilanba and Zhijin courtyard, we can see dolomites that are exposed at different locations, have different layers, and vary greatly in thickness (from several meters to over a hundred meters). The thickness is generally less than 100 m. The lithology varies greatly, including the pure limestone zone (de-dolomitization), dolomite and limestone zone, and the whole dolomite zone. The formation is as thick as 300−500 m in areas from Dushan to Weining, and several meters to tens of meters thick near the upwarped area in central Guizhou.

Brachiopods include Gondolina sp., Striatifera sp., etc. Coral fossils are distributed around Weining, Huishui and Dushan, mainly Yuanophyllum sp., Heterocaninia sp., Palaeosmilia sp., Aulina sp., etc. There are also Fusulinids Eostaffella sp., Millerella sp. and Pseudostaffella sp. At Dewu, Shuicheng, Ammonoids Homoceras, etc. are also found. Most of the elements in brachiopods and corals are continued from the underlying strata.

It is interpreted as platform-neritic sediments