Naomugen Fm
Type Locality and Naming
Central-Eastern Inner Mongolia. The naming section is located in Haliute 6 km southeast of Nomogen and Taban Tolgoi 4 km east of Haliute, in Siziwang Banner northeast of Ulan Qab City, Inner Mongolia; the reference section is in a drill well northeast of Naogangdai, Siziwang Banner. Named by the First Regional Geological Survey Party, Inner Mongolia, in 1974–1975, and formally published by Zhou Mingzhen, Qi Tao and Li Rong in 1976.
Synonym: Nomogen Fm
Lithology and Thickness
Surface survey and drilling reveal that Lower part is marked by brownish red and grayish green mudstone and light red fine sandstone and muddy sandstone with grayish white pebbly sandstone; and Upper part is brownish red mudstone with grayish green mudstone containing calcareous concretions, gypsum and celestine. The strata exposed on the surface are mainly those of the upper part. The apparent thickness is generally 16–19 m (according to the well record the thickness of the formation may be over 172 m, but it remains to be further confirmed).
Relationships and Distribution
Lower contact
It has a disconformable contact with the underlying strata (Erlian Fm of Cretaceous)
Upper contact
It has a conformable or disconformable contact with the overlying Eocene (Arshanto Fm?). The formation is incomplete in the area and usually covered by the Eocene or Quaternary.
Regional extent
This formation is distributed in the Jiang’an livestock farm, mouth of the Shara Murun River, Erden Obo and Naomugen in the northern part of Siziwang Banner and in the area from Arshantou to Nariyin Obo in Sonid Right Banner, but is best developed in the Shara Murun area.
GeoJSON
Fossils
The Naomugen Formation contains the mammal fauna characterized by abundant Multituberculata, Notoungulata and Pseudictopidae. This fauna at least includes 7 orders and 15 species; the main elements are Sphenopsalis nobilis, Lambadopsalis bulla, Pastoralodon lacustris, Sarcodon pygmaeus, Pseudictops lophiodon, Mimotona Borealis, Dissacus? sp., Plagiocristodon serratus and Palaeostylops iturus. In addition, charophytes include such species as Gobichara deserta, Nemegtichara prima and Peckichara lefeldi.
Because more than a half of the elements of the Naomugen fauna are the known elements of the Gashato fauna of the People’s Republic of Mongolia, the two faunas should belong to the same age. In comparison with the Taizicun fauna in Xinjiang, from the advanced level, the ages of the two fossil localities should be equivalent despite the difference in the composition of the groups.
Age
Depositional setting
It is suggested to lacustrine deposits.
Additional Information