Minbugou Fm
Type Locality and Naming
The type section is located at Minbugou, 25 km northwest of Wenxian County, Gansu Province. It was named by Ye Maoquan et al. in 1960; Qin Feng and Gan Yiyan formally quoted it in 1976.
Lithology and Thickness
Siltstone. The formation is composed of dark-gray and grayish-green thin-bedded clayey siltstone, calcareous siltstone and sandy shale intercalated with thin- to medium-bedded sandstone, iron-bearing sandstone, quartz sandstone and a few calcarenite thin-beds or nodules. Some ferruginous nodules are intercalated within the siltstone, occasionally with thin beds of chamositic hematite. In the calcareous siltstone occur several small shelly patch reefs or coral reef buildups. Ripple marks are fairly well developed on the sandstone surfaces. It is 346 m thick at its thickest point in Minbugou, but eastwards at Linjiang area it becomes thinner, only 113-116 m thick.
Relationships and Distribution
Lower contact
The formation conformably overlies on the Xigou Fm.
Upper contact
The formation disconformably underlies the Lengbuzi Fm.
Regional extent
The formation is widely distributed in the southern area of West Qinling. It is 346 m thick at its thickest point in Minbugou, but eastwards at Linjiang area it becomes thinner, only 113-116 m thick.
GeoJSON
Fossils
It yields abundant brachiopods and corals; the lower part bears coral Favosites regularrissimus, Squameofavosites obliquespinus, and the upper part yields brachiopods Xenospirifer fongi, Athyrisina squamosa and coral Calceola sandalina arcuata.
Age
Depositional setting
It is interpreted as a shore facies.
Additional Information
This formation is important for its iron ore deposits in the southern area of West Qinling and is widely distributed in this area.