Yanxi Fm
Type Locality and Naming
The type section is at Yanxi in Xinhua County, Hunan. The Yanxi Fm was named by Wang Chaoxiang and Bian Xiaozeng (1949). Following the naming of the Yanxi Fm, Jin Yuqin et al. (1964) remeasured the type section, and reported four graptolite zones.
Synonym: (烟溪组)
Lithology and Thickness
The Yanxi Fm is composed of thick-bedded black carbonaceous and siliceous slate. At the type area, it is 63 m thick.
Relationships and Distribution
Lower contact
The Yanxi Fm can be distinguished from the yellowish green slaty shale at the top of the underlying Qiaotingzi Fm based on its characteristic lithology of black carbonaceous and siliceous shale, and its lower boundary is at the base of the U. austrodentatus zone.
Upper contact
The upper boundary is marked by the yellow-greyish white shale at the base of the overlying Modaoxi Fm
Regional extent
The Yanxi Fm is present exposed in central Hunan. In Shuangfeng County, it is 50 m thick, and northward to Taojiang County, it decreases to 6 m in thickness.
GeoJSON
Fossils
This formation includes four graptolite zones, in ascending order, N. fasciculatus zone, P. elegans zone, H. teretiusculus zone and N. gracilis zone.
Age
Depositional setting
Additional Information