Chishanwu Fm
Type Locality and Naming
It was named by Chen Qishi in 1991. The naming section is located in the area of Chishanwu about 5 km south of the Changshan County town, Zhejiang Province.
Synonym: （赤山坞组）
Lithology and Thickness
Lower part of it is composed of grey-white quartz-conglomerate, sandy conglomerate, sandstone, siltstone, grey-black mudstone, carbonaceous mudstone and lenticular coal layers, with a thickness of about 150 m. Upper part is grey-white medium-, and fine-grained quartz-sandstone, siltstone, carbonaceous shale and lenticular coal layers, with a thickness of about 150 m; while its upper part is composed of multiple alternation of grey-white, medium-, and fine-grained quartz-sandstone, siltstone, carbonaceous shale and coal beds, with a thickness of about 401 m.
Relationships and Distribution
Lower contact
Its basal part overlies unconformably the Changwu Fm of the Upper Ordovician.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Majian Fm
Regional extent
The formation is distributed essentially in the Chishanwu area of Changshan County till Tongtou of Quzhou City, as well as in the Tanshi area of Jiangshan County till Dazhou of Quzhou City. Its lithology varies from place to place. The amount of quartz grains in the composition of the rocks is greater in the former, while in the latter it is the feldspar and quartz that play the predominant role in the composition of the rocks. The distribution of quartz-conglomerate and pebble-bearing coarse-grained sandstone in the basal part of the formation is consistent.
GeoJSON
Fossils
It yields plant fossils as represented by the Marattiopsis-Otozamites assemblage key members of which in the lower part are: Phlebopteris cf. polypodioides, P. woodwardi, Otozamites hsiang chiensis, O. cf. giganteus, O. indosinensis, O. molinianus, and in the upper part there are Coniptexis sp., Otozamites mixomorphus, Ptilophyllum spp., Nilssonia polymorpha. There are found occasionally bivalves.
Age
Depositional setting
The formation represents peri-lacustrine to lake-swamp facies coal-bearing deposits.
Additional Information