Tanglong Fm
Type Locality and Naming
It was named by Tan Xichou as the “Tanglong Horizon” in 1933. The naming section is located on the northern side of the Tongrilong Gully, Sandu region, Zixing County, Hunan Province.
Synonym: （唐垅组）
Lithology and Thickness
It is composed of light-grey, grey-black and grey-brown medium-bedded quartz-sandstones, intercalated with thin-bedded siltstone and mudstone, with the increase in the content of feldspar in the quartz-sandstone in the top part of the formation, and with the basal part of the latter being composed commonly of pebble-bearing sandstone and conglomerate, with a thickness of 50-224 m.
Relationships and Distribution
Lower contact
Its basal part is in an unconformable contact with the underlying Yangmeilong Fm
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Xintianmen Fm
Regional extent
In the Yanshou region of Rucheng County, the middle part of the formation is intercalated with diabase with a thickness of 43 m. In the Xintianmen area, argillaceous components in the rocks are increasing, and in the Sandu and Xintianmen regions, the formation is also intercalated with poor-quality coal beds. It is commonly in an unconformable contact with the underlying strata, while in the Rucheng area it overlies directly the late Paleozoic strata.
GeoJSON
Fossils
In the Yanshou region of Rucheng County, as well as in the Yizhang and the area north of Zixing-Rucheng zone the formation yields marine bivalves as represented by the Retroceramus heyuanensis-Parainoceramus matsumotoi assemblage, with the plant fossils belonging to the Marattiopsis- Otozamites assemblage of the Dictyophyllum-Clathropteris flora.
Age
Depositional setting
The formation is composed largely of continental deposits, but with minor marine deposits.
Additional Information