Yimen Fm
Type Locality and Naming
It was named by Ruan Weizhou as the Yimen Red Rock Beds in 1942. The naming locality is situated in the vicinity of the Yimen Township, Huili County, Sichuan Province, with its reference section being located in the Gaojiawanzi area, Yimen Township, Huili County.
Synonym: （益门组）
Lithology and Thickness
The formation is subdivided into three parts. Lower part is composed of grey-white and yellow-grey thick-bedded and massive fine-grained quartz-sandstones and siltstones, intercalated with purple mudstones and siltstones. Middle part is composed of purple mudstones and grey-white massive marls and brecciated limestones. Upper part consists largely of grey-white thick-bedded and massive fine-, and medium-grained quartz-sandstones, intercalated with purple and reddish mudstones. The total thickness is about 595 m. There are few differences in the lithology of the formation between various regions, but with a great variation in its thickness.
Relationships and Distribution
Lower contact
It is in a conformable contact with the underlying Baiguowan Fm (synonym for the Donggualing Fm, in south Sichuan region of column TJ78) or with the Baoding Fm (southernmost Sichuan, region of column TJ77).
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Xincun Fm
Regional extent
The formation is distributed in the Xide, Xichang, Zhaojue and Huili areas of southwestern Sichuan.
GeoJSON
Fossils
Its middle part yields fish fossils as represented by Lepidotus sp. and “conchostracan” fossils. In addition to the above-mentioned fossils, in other regions the formation yields also Reptilia fossils as represented by Bientherium sp.; bivalve fossils as represented by Psilunio sp. and Cuneopsis sp., as well as plant fossils.
Age
Depositional setting
Additional Information