Huanglong Fm
Type Locality and Naming
The type section is located at the west end of Chuanshan Mt., 3 km southwest of Shimamiao, Zhenjiang, Jiangsu; the reference section is at Jinsigang, Nanjing City. It was named by Li Siguang (J.S. Lee) and Zhu Sen in 1930.
Lithology and Thickness
Dolomite and Limestone. A suite of gray to light-gray thick-bedded massive micrite limestone and bioclastic limestone, with sparite at bottom; containing lime dolomite breccias and nodules, and yielding abundant fossils of fusulinids, corals and brachiopods. Thickness 80 m at type section.
In some areas, the dolomite in the lower part had been classified separately, e.g., it is attributed to the Laohudong Fm in Jiangsu, and the Dapu Fm in Guangxi. The formation is stable in lithology, and is clearly divided into two parts. The Lower part consists of dolomite or dolomitic limestone, with less fossils. In areas near land, e.g. northwestern Jiangxi, Hubei, Xuancheng and Jingxian of Anhui, clastic rocks such as sandstone and shale occur at the bottom, and there are Fe- and Mn-bearing layers in clastic rocks in northeastern and central Guangdong and in Leping of Jiangxi. The Upper part is composed of light-gray thick-bedded massive bioclastic limestone or bioclastic micrite limestone, rich in fossils. Dolomitic limestone is widely developed in Hunan, Guangdong et al., and locally being dolomite. Around Huangshi of Hubei and northern-central Zhejiang, there are intercalations of chert nodules; along Jiangshan-Jinhua of Zhejiang close to the Fujian-Zhejiang Oldland, both the upper and lower members of the formation contain large amounts of quartzose sandstone and mudstone.
It is relatively thin in Jiangsu, Zhejiang, Anhui, northwestern Jiangxi and Hunan, generally <100 m, being 70 m in coastal northern Jiangsu, 56−96 m in the Nanjing−Zhenjiang mountainous areas of southern Jiangsu, 50−100 m along Anji−Changhua of Zhejiang, 30−63 m along Hexian−Chaoxian of Anhui, 6−61 m in northwestern Jiangxi, and 55−139 m along Enshi−Jingshan of Hubei. Southward to Hunan, southern and central Jiangxi, and Guangdong, the thickness increases, generally 100−500 m, locally 570−800 m along Yangshan−Yangchun of Guangdong.
Relationships and Distribution
Lower contact
Conformable at type section: The bottom is demarcated from the gray-white thick-bedded lime dolomite of the underlying Laohudong Fm by the appearance of gray-white and carnation sparites. However, the Huanglong Fm has different contacts onto many other local formations throughout its wide distribution. For example, it is in conformable contact with the Lower Carboniferous Zimenqiao Fm in Guangdong and Hunan, but in disconformable contact with the Lower Carboniferous−Proterozoic strata in other areas, and in unconformable contact with Proterozoic strata in some local areas such as Shang’an of Jiangxi.
Upper contact
Conformable at type section: the top is demarcated by the appearance of dark-gray thick-bedded limestone of the Chuanshan Fm at the type section. Through much of its wide distribution, it is conformable overlain by the Maping Fm. But at Chuanshan of Zhenjiang, it is in disconformable contact with the Chuanshan Fm; while at Ruichang of Jiangxi, Tongshan of Hubei, Xibanli of Daye et al., it is in disconformable contact with the Qixia Fm.
Regional extent
Widely distributed in Jiangsu, Zhejiang, Anhui, Jiangxi, Hubei, Hunan, Guangdong and other provinces
GeoJSON
Fossils
In the Nanjing-Zhenjiang areas the fossil zones include (in ascending order): the Fusulinids Profusulinella and Fusulinella beedeina zones, of which the latter is divided into three subzones: the Fusulinella praebocki, Beedeina cheni and Fusulina quaisicylidrica subzones; the Brachiopods Choristites mosquensis assemblage and corals dominated by Lithostrotionaella stylaxia, L. belinskiensis, Caninia lipoensis, Chaetetes lungtanensis, etc.
Age
Depositional setting
It is interpreted as normal littoral-neritic deposits
Additional Information