Fanjiatun Fm
(20), Guadupian Epoch (Middle Permian)
Type Locality and Naming
The type section is located at the Fanjiatun Limestone Mine, Dashuihe, Yongji County, Jilin Province, while the reference section is situated at the Korean-nation Village to the east of Shuanghe Township and Zhoujiayao Village of Shuangyang County. It was named by the Regional Geological Survey Party under the Changchun Geological College in 1960, and was cited officially by Tao Nanshong in 1975.
Lithology and Thickness
Clastics and Volcaniclastics, intercalated with limestone. Lower part consists of grey-black and grey-green fine-grained sandstone and siltstone, intercalated with variegated sandy slate, with a thickness of over 484 m. Middle part consists of grey-white thick-bedded limestone, intercalated with green and purple tuff, tuffaceous sandstone and sandy conglomerate, with a thickness of 265 m. Upper part of the formation consists of interbeds of variegated tuffaceous sandstone, sandy conglomerate, black metamorphosed siltstone and shale, with a thickness of 725 m. Total thickness of 1474-2413 m.
Relationships and Distribution
Lower contact
Unconformable (?) to the underlying Daheshen Fm; but base of the formation has not been found in the majority of sections. At the Dahesheng of the Changshan Country, the contact between the formation and its underlying Daheshen Fm seem to be lithologically continuous, but the sequences of the Fusulinida assemblages yielded by the two formations are discontinuous. Therefore, it is inferable that the contact is disconformable.
Upper contact
Disconformable contact with the overlying Yilaxi Fm.
Regional extent
Distributed in the Shulan, Jiutai, Shuangyang, Panshi, Huadian and Jiaohe River areas of Jilin Province. The volcaniclastic rocks of the formation are thickening from south to north, with the limestone being thinning whose thickness is of over 10 m only, reaching as less as 35 cm, while up to the Fanjia Village of Yongji County and Yumuqiaozi of Huadian County the thickness is getting as great as over a hundred m.
GeoJSON
Fossils
Limestone in the type section has abundant animal fossils, including Fusulinida such as Neoschwagerina, Verbeekina, Chusenella, and Yabeina; Corals represented the Waagenophyllum-Wentzelella assemblage; and Brachiopods represented by Waagenoconcha irginae, Yakovlevia, Stritifera, Stepanoviella tschernyschewi, Anidanthus ussuricus, Leptodus tenuis, Neospirifer ravana, Spiriferella. The Jilin Regional Geological Survey Party discovered Ammonoids there in 1978 such as Daubichites, Tauroceras, Metalegoceras and Waagenoceras; Bryozoa represented by the Hayasakapora-Girtypora-Coscinotrypa assemblage; and Conulariids represented by Jilinoconularia. The clastic rocks of the Upper part of the formation yields plant fossils (phytolites) such as Pecopteris, Paracalamites, as well as Estheria.
Age
Depositional setting
Lower part of the formation is interpreted as volcanic-arc marginal littoral shallow-sea deposits; and its top part of a suite of fine clastic rocks with a well-developed rhythm is interpreted as deep-water turbidite-facies deposits.
Additional Information