Yuhuangding Fm
Type Locality and Naming
The naming section is located from Yuhuangding, Danjiang City (Junxian County), Hubei, to Dacangfang, Xichuan, Henan, and the reference section is located in the area from Nüyangquan to Zhanggou, Danjiang City, Hubei. Named by the Petroleum Party of the Henan Bureau of Geology in 1959.
Lithology and Thickness
Lower part is grayish or light red marlstone and grayish yellow or light gray sandy mudstone and mudstone, with purplish red mudstone, containing calcareous concretions. Upper part is gray or grayish white marlstone with sandy mudstone and mudstone. The lithofacies varies greatly from east to west. In the east marlstone predominates; it thins toward both sides and is replaced gradually by sandy mudstone and sandstone. The thickness is up to 330–700 m. similar horizons are found in wells in the Nanyang basin.
Relationships and Distribution
Lower contact
The formation has a disconformable contact with the underlying Upper Cretaceous Hugang Fm. However, in this same region of Hubei border to SE Henan, there is also the uppermost Cretaceous Sigou Fm.
Upper contact
The formation has a conformable contact with the overlying Early to Middle Eocene Dacangfang Fm.
Regional extent
The formation is mainly distributed at Wenjiaping, Dahupo, Yuhuangding and Jiajiazhai in the eastern part of the Liguanqiao basin (or Xichuan basin) and at Huangying, Songping, Da’ao and Qingtangling in the western part.
GeoJSON
Fossils
In addition to birds (Zhongyuanus xichuanensis), the Yuhuangding fauna also contains mammals, gastropods and ostracods. The mammals are Rhombomylus sp., Advenimus hupeiensis, Asiocoryphodon conicus, Heterocoryphodon flerowi (=Coryphodon flerowi, =Manteodon flerowi) and Heptodon sp. According to Li Yuntong (1983), there are at least 7 genera and 13 species, mainly including Bithynia magna, B. lordostoma, Australorbis junxianensis, Aplexa xichuanensis, Palaeoluca orientalis and Pupoides (Ischnopupoides) antiquus. The ostracods are mainly Cypris henanensis in addition to Eucypris subtriangulata.
Age
Depositional setting
It is interpreted to lacustrine deposits.
Additional Information
Age Span:
Beginning stage: Thanetian
Fraction up in beginning stage: 0.0
Beginning date (Ma):
Ending stage: Ypresian
Fraction up in ending stage: 0.5
Ending date (Ma):
Depositional setting:
It is interpreted to lacustrine deposits.
Depositional-pattern:
Additional Information
Because the lithology of the Paleocene Baiying Formation is relatively similar to that of the Yuhuangding Fm and no fossil with an exact age has been found, the Baiying Fm is now temporarily assigned to the Yuhuangding Fm. As to the upper member of the Yuhuangding Formation defined by Ma Ancheng et al., as its lithology and its contained Zhanggou Fauna are more similar to those of the Dacangfang Fm, from an analysis of relevant fossil forms, now it seems that this member might be assigned to the Dacangfang Fm although their ages are slightly different.