Yian Fm
Type Locality and Naming
Songliao Basin. The naming section is located in well No.59-4 in Yian County in northwestern Heilongjiang. Named the Yian Bed by the Third Regional Geological Party, Songliao Petroleum Prospecting Party in 1959, and the age was assigned to Pliocene at that time. In 1960 Li Hengrang, Yan Huaiyu et al. renamed it the Yian Formation.
Lithology and Thickness
Grayish green mudstone and sandstone and black carbonaceous shale with lignite beds, containing calcareous concretions; the lower part is intercalated with marlstone and locally with kaolin, and the base is sandy conglomerate. The thickness is 55–260 m.
Relationships and Distribution
Lower contact
The formation has an unconformable contact with the underlying Cretaceous Mingshui Fm.
Upper contact
Unconformable contact with the overlying Quaternary. [or, regionally, overlain by Daan Fm)
Regional extent
It is mainly distributed in Yian County and Anda City.
GeoJSON
Fossils
It yields sporopollen, the bivalves Sphaerium, the gastropods Panorbis and the ostracods Candona and Candoniella.
According to the fact that its sporopollen is somewhat similar to the Fushun flora in Liaoning and its correlation with the horizons in its adjacent areas, the age of this formation is probably Eocene–Oligocene.
Age
Depositional setting
Additional Information