Chengchao Fm
Type Locality and Naming
It was named as the “Chengchao Member” by Chen Gongxin in 1983, and was first cited publicly and was renamed as “Chengchao Formation” by the Hubei Geological Bureau in 1990. The naming section is located in the vicinity of the Chengchao area, Ercheng County, Hubei Province.
Synonym: （程潮组）
Lithology and Thickness
It begins with a large set of feldspar-quartz sandstone, and is gradating upwards into siltstone and mudstone, intercalated with coal layers, constituting three-sedimentary rhythms, with the quartz-sandstone at its base being consistent all over the region, and being possessed of large-scale monoclinal beddings. In parts of the areas there occur 1-3 layers of conglomerate, with a thickness of 172 m.
Relationships and Distribution
Lower contact
The basal part of the formation is in a disconformable contact with the underlying Jigongshan Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Dawangchong Fm
Regional extent
It is distributed essentially in the Chengchao and Bishidu areas of Ercheng County, Jinshandian and Damashan areas of Dayie County, and Tuditang area of Wuchang County. It has its exposures also in the areas of Ma’anshan and Qiujia of Wuchang County, in the suburbs of Puqi County Town, Caojia of Ercheng County, and in Hekou area of Huangshi City. Its lithology is commonly more or less consistent, and a good development of it can be seen in a zone stretching form Dayie in the central part of its distribution region to Ercheng, with a thickness varying from 60 m to 170 m, and being thinning towards both the east and west of the region.
GeoJSON
Fossils
It yields bivalves as represented by Apseudocardinia cf. dazuensis, Pseudocardinia cf. letragonalis, and Tutuella cf. rotunda; represented insects fossils as represented by Hubeia tenuis, Wuchangia lalilimbata, Wuchangicavabus latus and Cavicaranus lucersus. The plant fossils contained there belong to the Codites princeps-Ptilophyllum assemblage of the Dictyophyllum-Clathropteris flora, important members of which are Coniopteris hymenophylloides, Ptilophyllum pectin, P. contiguum, Otozamites indosinensis and Nilssonia innuyei.
Age
Depositional setting
The Chengchao Formation belongs mainly to fluvial deposits, forming swamp facies locally.
Additional Information
The term “Wuchang Coal Series” or “Wuchang Group” represents a larger substance of a lithostratigraphic unit, and has long been used in the practice. And it is unreasonable to use the term “Wuchang Formation”; besides, various authors tend to give it different implications when using it. So, in order to avoid confusion in its application, it is advisable to keep the term “Wuchang Group” unchanged, and to create a new formation instead.