YangjiawanNeogene Fm
Type Locality and Naming
The type section is located at the “Wangjiawan section” (E106°47′, N33°12′) of the Tuanzhuang town, about 15 km east to Mianxian County, Hanzhong District, Shaanxi Province. It was named by Tang et al. (1988). BGMRS(Shaanxi)P (1998) employed this formation.
Gao et al. (2014b) pointed out that the name of “Yangjiawan Fm” has already been occupied by the Cambrian Yangjiawan Fm in Guizhou Province, which was named by Yang et al. (1963) and has priority. A new name should be given to replace the Neogene “Yangjiawan Fm” in Shaanxi Province in future.
Lithology and Thickness
It is a series of lacustrine sediments formed by two depositional cycles. Each cycle is characterized by its lower gravels and upper motley clays, and contains small amount calcareous or manganese-iron nodules. It contains abundant fossil mammals, fishes, turtles, aves, and sporopollens, and it also produces bentonite ores. Its thickness is in range of 30~40 m.
Relationships and Distribution
Lower contact
In the type section, the Yangjiawan Fm conformably contacts with the underlying Upper Miocene deposits. [Regionally – see Age below, the next older unit is the Youhe Fm]
Upper contact
In the type section, the Yangjiawan Fm unconformably contacts with the overlying Lower Pleistocene Zhoujiawan Fm.
Regional extent
In other areas, this formation is directly overlapping the underlying basal rocks. This formation is distributed to Yangjiawan of Mianxian and Dengjiamiao of Yangxian in the Hanzhong Basin, Shaanxi Province.
GeoJSON
Fossils
Turtle: Testudinidae indet. Fish: Cyprinus sp. Avian: Aves indet. Mammals: Mimomys hanzhongicus, Sinomastodon hanjiangensis, Stegodon zdanskyi, Stegolophodon xixiangensis, Gaindatherium cf. G. browni, ? Chilotherium sp., Hipparion plocodus, Hipparion sp., Tapirus sp., Paracamelus sp., Dicoryphochoerus sp., Cervavitus cf. C. demissus, Metacervulus cf. M. capreolinus. Sporopollens: Chenopodiaceae, Pinus, Humulus, Betula, Polygonaceae (Tang et al., 1988).
Age
Depositional setting
It is interpreted as river-lake environment.
Additional Information