Tangding Fm
Type Locality and Naming
The type section is located in west of Luofu Town of Nandan County, Guangxi. It was named by No. 5 Prospecting Team of Geological Ministry in 1961. Formerly lower part of a generalized (and no longer used) Chehe Fm – see note for that entry.
Lithology and Thickness
Mudstone. The formation, about 430 m thick, is characterized by purplish-gray and grayish-black mudstone with carbonaceous mudstone interbeds, and intercalated with dolomitic marl and quartz sandstone in the uppermost portion. The Tangding Fm is characterized by the several beds of micritic and clayey limestones in the lower part
[Figure Outcrops of Tangding Formation in the type locality, note that the weathered surface is yellow purplish red in color, but black color seen in the drilling core]
Relationships and Distribution
Lower contact
Conformably underlain by the Pojiao Fm.
Upper contact
Conformably overlain by the Luofu Fm; the contact being placed at the appearance of a sandstone bed.
Regional extent
The formation is mainly distributed in Nandan, Hechi, Wuxu, nanning, etc. Westward to Guangxi-Guizhou border the Formation can be traced in the Changli anticline core, where exposed the Devonian rocks belonging to Tangding Fm and Luofu Fm..
GeoJSON
Fossils
The formation contains an upward succession of tentaculites from Nowakia subtilis, N. mana, N. praecursor, N. barrandei, N. cancellata, N. richteri, N. holyensis to N. sulcata zones. Ammonoids Anetoceras (Erbenoceras) elliticum, Mimagoniatites fecunda, Teicherticeras nantanense, Anacestes (Latanacestes) noggerati, Pinacites jugleri. Trilobites: Plagiolaria nandanensis, Ductina vietnanmica, Cyphaspides orientalis. Brachiopods: Nabiaoia pusilla, Plectodonta biplexa, Luofuia delicata, Paraplicanoplia nana, etc.
[Figure – Ammonoid Anetoceras obliquecostatum (Ruan), lateral view, X 1, Lower part of Tangding Formation in Luofu,]
Age
Depositional setting
It is interpreted as an anoxic deep-water facies
Additional Information