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Yuyang Formation

Yuyang Fm

Period: 
Cretaceous, Paleogene

Age Interval: 
Late Cretaceous? (or into Paleocene), K2yy


Province: 
Hubei

Type Locality and Naming

The Yuyang Formation was named by the Petroleum Exploration Department of the Jianghan Oilfield in 1963.

Synonym: The Stratigraphic Chart (1974) renamed it as the Jiangling Fm. Both are of Late Cretaceous age. Guan Shaozheng (1979) referred it to the Paleogene Xingou Fm based on the microfossils. The type locality is in the Yuyang town based on boreholes.


Lithology and Thickness

The Yuyang Formation is a group of sandstone and conglomerate, bearing clay and gypsum beds. Lower part is interbedded by purple mudstone, sandstone and calcareous gypsum sandstones; Upper part is characterized by dark grey mudstone, brownish mudstone and gypsum beds intercalated with basalt. It is over 1000 m thick.


Lithology Pattern: 
Gypsiferous claystone


Relationships and Distribution

Lower contact

Not given; but Regionally (Cretaceous column 33b in central Hubei), there is also a Campanian through Danian(?) Gonganzhai Fm

Upper contact

Conformable or disconformable with the earliest Eocene Xingouzui Fm

Regional extent

The Yuyang Formation is wide spread in the area of 2800 km2 of the Jianghan Basin.


GeoJSON

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Fossils

Microfossils are abundant in the formation. In the upper part yields Ostracods Talicypridea reticulate, T. jianghanensis, T. brevis, Cypridea (Pseudocypridina) aversa, C. (Morinia) xindianensis, Quadracypris cf. favosa, Mongolianella oblonga, Darwinula mianyangenensis, Candona sinensis; charophytes Charites tenuis, C. longiconica, C. guanpingensis, Peckichara dangyangensis, Grambastichara yunyangensis, Gyrogona hubeiensis; and spore and pollen. The lower part contains ostracods Quadracypris jiadianensis, Cyprois jiadianensis; charophytes Porochara anluensis, P. jingshanensis, Maedlerisphaera jiadianensis, Euaclistochara mundula, Obtusochara cylindrical and spore and pollen.


Age 

Was indicated as "Late Cretaceous" in Cretaceous suite; but if "Conformable or disconformable with the earliest Eocene Xingouzui Fm" (from Paleogene suite), then "for graphic purposes" shown here as mid-Selandian to mid-Thanetian, and underlain by Gonganzhai Fm (which was indicated as extending into Danian).

Age Span: 

    Beginning stage: 
Selandian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
60.45

    Ending stage: 
Thanetian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
57.62

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao