Donglanggou Fm
Type Locality and Naming
Chen Kai and Xiong Yongxian erected the Donglanggou Agglomerate at Donglanggou of Dahuichang in the Western Hills of Beijing. The reference section is at the Shooting Range west of Dahuichang in the Fengtai District of Beijing.
The Donglanggou Agglomerate represents the volcanic agglomerate under the Dahuichang series and over the green rhyolite in the Dahuichang area, which was attributed to Early Cretaceous. In 1979 Wang Ziqiang et all called it the Donglanggou Agglomerate Formation and assigned it to Late Jurassic. In 1982 Hong Youchong et al called it the Donglanggou Formation and attributed it to Late Jurassic. In 1994 Xiao Zongzheng reassigned the formation to Early Cretaceous.
Lithology and Thickness
The Donglanggou Formation is mainly built up by purple gray andesitic breccia tuff with basalt andesite, bearing the Jehol fauna in the gray green sediment tuff. It is 148.1 m thick.
Relationships and Distribution
Lower contact
Its base is distinguished from dolomite of the Middle Proterozoic Wumishan Fm by the occurrence of gray purple andesitic breccia tuff. Its base generally overlaps the Middle Proterozoic Wumishan Fm and locally contacts with the older strata by fault.
Upper contact
Its top is bounded by the occurrence of brown yellow thick-bedded conglomerate and gravel-bearing grit at the base of the Dahuichang Fm. It is in conformable contact with the overlying Dahuichang Fm and locally by fault.
Regional extent
The Donglanggou Formation occurs in the hilly area north to the line linking Xinzhuang-Dahuichang-Yangjuantou. The basalt andesite intercalations are thickest from the north of Xinzhuang to the Chemical Plant.
GeoJSON
Fossils
The formation yields bivalves Ferganoconcha subcentralis; gastropods Probaicalia vitimensis, Amnicola cf. yunnanensis; ostracods Cypridea unicostata, C. voldensis praecursor, C. yaojiansis; Fish Sinomia sp.
Age
Depositional setting
Additional Information