Ulanhudag Fm
Type Locality and Naming
The type section is in Baiyanhua Hill in Shetai Township, Urad Qianqi, Inner Mongolia. The Ulanhudag Fm was named by Lin Baoyu et al. in 1984.
Synonym: (乌兰胡同组）
Lithology and Thickness
The formation is composed dominantly of dark gray, grayish black medium-bedded limestone intercalated with thin-bedded limestone and calcareous sandstone. In the type area, the Ulanhudag Fm is 62 m thick.
Relationships and Distribution
Lower contact
It rests conformably on the dolomite and dolomitic limestone of the Erhagong Fm
Upper contact
It is disconformably overlain by weathered thin-bedded limestone at the base of the Baiyanhuashan Fm (Lin et al., 1984) [not yet an entry in Lexicon yet; but the Bayan Hua Shan Fm is a thick-bedded limestone and knotty limestone intercalated with flint bands = siliceous limestone.]. At Shanheila in Shetai Town, it is disconformably overlain by the Carboniferous. Next younger regional unit in present lexicon is the Xuniwusu Fm of middle to late Silurian flysch.
Regional extent
At Shanheila in Shetai Town, only the strata equivalent to the E. typus-T. sishuiensis zone is developed. It is composed of 63 m thick limestone and calcareous dolomite. Based on Protopanderodus insculptus found from the top of the Ulanhudag Fm, the upper boundary of the Ulanhudag Fm is equivalent to the top boundary of the Baota Fm in Yichang, Hubei.
GeoJSON
Fossils
This stratigraphic unit yields conodonts of lower Erismodus typus-Tasmanognathus sishuiensis assemblage, upper Yaoxinaognathus neimengguensis assemblage (An et al., 1990) and cephalopods, and is equivalent to the C. (Diplacanthograptus) peltifer zone to D. clingani zone.
Age
Depositional setting
Additional Information