Huangnigang Fm
Type Locality and Naming
The type section is located at southern end of Huangnigang Village about 3 km north of the Jiangshan County seat, Zhejiang Province. This was evolved from Huangnigang Shale established by Lu Yanhao et al. (1955). Zhang Wentang (1962) changed the name into Huangnigang Fm which is followed up to now.
Synonym: (黄泥岗组）
Lithology and Thickness
The formation is yellowish-green, locally purplish-red calcareous mudstone containing limestone nodules, silty mudstone intercalated with argillaceous nodular limestone. In the type area, the Huangnigang Fm is 45 m thick.
Relationships and Distribution
Lower contact
Its bottom is distinguished from the underlying medium-bedded limestone of Yanwashan Fm by the appearance of mudstone. It is in a conformable contact.
Upper contact
It is in conformable contact with overlying strata (Changwu Fm, Sanqushan Fm or Yuqian Fm).
Regional extent
It can be roughly correlated with Linxiang Fm in Yangtze Gorges area and Jiancaogou Fm in northern Guizhou Province. It is a suite of neritic shelly facies sediments with persistent rock facies and wide distribution, and is seen mainly in western Zhejiang (17.5-45 m thick), northwestern Zhejiang (65-110 m), southern Anhui (59-134 m) and around Wuning, Jiangxi (6-44.5 m). In Nanchong and Zaoxi in northern part of Yushan County, Jiangxi, the equivalent strata change facially into a suite of calcareous or nodular limestone-bearing silty shale, shale and small amounts of greywacke, with scarce fossils and over 100 m thick (Jiangxi Bureau of Geology and Mineral Resources, 1984).
GeoJSON
Fossils
It has abundant fossils, mainly trilobites, ostracodes, brachiopods and cystoids, of which the trilobites may compose Nankinolithus nankinensis zone (Lu Yanhao et al., 1955; Lai Caigen et al., 1982; Zhejiang Bureau of Geology and Mineral Resources, 1989).
Age
Depositional setting
Additional Information