Dongma'anshan Fm
Type Locality and Naming
Wang Guixiang was named in 1979. The named profile is located in East Ma'an Mountain (= Dong Ma'an Shan"), 2 km southeast of Yueshan Town, Huaining County, Anhui. Uppermost formation in Qinglong Gr.
Synonym: Dongmaanshan Fm
Lithology and Thickness
The lower section is gray-white thin to thick silt crystal dolomite and dolomitic limestone, mixed with gray thin to middle stratified stratiform or stratolite silt crystal dolomite, containing oolitic sandy dolomite, oolitic dolomite, etc.; the upper section is gray, flesh-red dolomite and salt breccia. The thickness is 17 to 563 m.
Relationships and Distribution
Lower contact
At the bottom, dolomites are in integrated contact with the underlying Lower Triassic Nanlinghu Fm
Upper contact
At the top, dolomites are in integrated contact with the overlying Middle Triassic Huangmaqing Fm
Regional extent
This formation is a semi-closed salty basin deposit, mainly distributed on both banks of the Yangtze River in Anhui. It is well exposed in Susong, Huaining, Guichi, Tongling, Nanling and other places. The lithology and thickness vary greatly, from west to the thickness of the east is gradually reduced, the surface is exposed as salt-soluble breccia, and the underground is gypsum layer. In Jiucaishan, Susong, this group has obvious vertical dichotomy, with a thickness of 674 m; Guichi Wutian is a single gray dolomite with a thickness of more than 90 m; Tongling watershed is dolomite and dolomitic limestone with a thickness of more than 115 m; Tongling Yecun Fm is also a single gray dolomite and dolomitic limestone, the thickness is reduced to 54 m; Nanling Maqiao Wufang Village is mainly salt-soluble breccia, only 40-50 m thick; to Fanchang Sanshan Street , Baima Mountain and other places, only sporadic exposure.
GeoJSON
Fossils
Biological fossils are relatively rare, including bivalves, gastropods, foraminifera, and ostracods. Dolomitic limestone interbedded with bivalves in the lower section Costatoria? sp., Asoella illyrica, Unionites sp., Chlamys sp., Entolium? discites, Bakevellia? sp. and Conodont Neospathodus longidentata etc.
Age
Depositional setting
Additional Information
The East Ma'anshan Fm originally refers to a set of dolomites and salts distributed on both banks of the Yangtze River in Anhui. Soluble breccia. In 1976, Chen Chuzhen and Min Qingkui named the Xujiashan section in Cangbomen, Jiangning County, Jiangsu Province, and named the corresponding strata "Xujiashan Fm ". In 1980, Wu Qiqie et al. thought that the meaning of "Xujiashan Fm" was ambiguous and suggested to abandon the "Xujiashan Fm " and establish Zhouchongcun Fm based on the underground data of Zhouchongcun gypsum mine in Nanjing suburb. In 1992, Wang Zunzhou and others believed that Zhouchongcun Fm was a synonym of East Ma'anshan, and therefore proposed to abandon Zhouchongcun Fm. This lexicon follows it.