Dahuichang Fm
Type Locality and Naming
Xie Jiarong erected the Dahuichang series in 1933. The section for the designation is at Dahuichang of Beijing and the reference section is in the east channel and the west Shooting Range of Dahuichang, Fengtai District, Beijing.
The Dahuichang series represents the rock series consisting of black shale and sandstone with conglomerate over the Andesite Formation and under the "Paleogene" XinzhuangBeijing Fm series, which was re-assigned to Early Cretaceous. In 1979 Wang Ziqiang et al called it the Dahuichang Black Shale Formation, and assigned it to Late Jurassic. In 1982 Hong Chongyou et al called it the Dahuichang Formation and still assigned it to Late Jurassic. In 1990 Xiao Zongzheng et al referred it to Early Cretaceous.
Lithology and Thickness
The Dahuichang Formation mainly comprises yellow green sandy conglomerate, sandstone and mudstone. Its lower part is built up by yellow-green-gray black shale yielding abundant Jehol fauna. The Dahuichang Formation is 127.8 m thick.
Relationships and Distribution
Lower contact
Its conformably basal part, built up by black shale, brown yellow thick-bedded conglomerate and gravel-bearing grit, is differentiated from the gray green tuff of the underlying Donglanggou Fm.
Upper contact
It contacts by fault, locally disconformably with the overlying XinzhuangBeijing Fm.
Regional extent
The present formation mainly occurs in the Xinzhuang, Dahuichang, Houpuying and Yangjuantou areas.
GeoJSON
Fossils
The formation yields bivalves Sphaerium yanbianensis, S. jeholens, Gastropods Probaicalia gerassimovi; Ostracods Cypridea protracta, Rhinocypris joveata; Estheria Eosestheria middendorfii, Diestheria longinqua; insects Wphemeropsis trisetalis; Pisces Lycoptera davidi.
Age
Depositional setting
It is of lacustrine facies.
Additional Information