Cangxi Fm
Type Locality and Naming
Sichuan Basin – central. The Cangxi Formation was erected by the Sichuan Navigation Survey Team in 1980. The type section for the designation is in Tazishan of Cangxi County, Sichuan Province.
The Cangxi Formation stands for the set of clastic rocks dominated by sandstone in Sandaogou-Guanting-Tazishan of Cangxi of Liangzhong County, in the northern part of the Sichuan basin, which has been assigned to Early Cretaceous. It is the lower-middle formation of the Chengqiangyan Gr in the northern part of the Sichuan basin.
Synonym: Qiqusi Fm
Lithology and Thickness
This formation is dominated by gray purple and gray green lithic sandy conglomerate, intercalated with brick-red and brown red siltstone and mudstone. It is 452.5 m thick.
Relationships and Distribution
Lower contact
The lower boundary is marked by the “Gaojiashan Conglomerate” and contacts conformably with the underlying Penglaizhen Fm (latest Jurassic) comprising green red mudstone interbedded with gray purple fine sandstone and siltstone.
Upper contact
The Cangxi Formation is in conformable contact with the overlying Bailong Fm consisting of purple gray calcareous conglomerate and lithic sandstone.
Regional extent
The formation is lithologically characterized by the development of large-scale cross-beddings and parallel beddings, and varies considerably in thickness, thinner in southwest and thicker in northeast. It is 450 m thick in Cangxi, 540 m in Lingyun of Bazhong, 480 m in Tongjiang, 200-350 m in Zitong, Jiangyou and Deyang, 200 m in Yanting and Santai, and less than 200 m in Jianyang and Zhongjiang.
GeoJSON
Fossils
The formation yields ostracods Jingguella elliptica, Deyangia reniformis, D.subreniformis, Bisulcocypris carinata; bivalves Pseudohyxioides cangxiensiis, P.trigonius, P.trigonius, P.laevigotus, Trigonioides cf. yunanensis; ostracods Jingguella sichuanensis, Pinnocypridea subovata, Cypridea shantaiensis, Deyangia postacuta, D.prona, D.lushanensis, Rhinocypris dorsoconcava, Candona sp. in the Jiangzhong area; and bivalves Nakamuranaia chingshanensis, Nippononaia sp. Trigonioides yunanensis, and Pseudohysioides congxiensis.
Age
Depositional setting
It is of fluvial facies.
Additional Information