Xinhe Fm
Type Locality and Naming
It was named by the No. 1 Regional Survey Party under the Geological Bureau of Gansu Province in 1967, and was first cited publicly by the Compiler
Jingeng Sha (coordinator) Group for the Regional Stratigraphic Chart of Gansu Province in 1980. The naming section is located at the Wangjiawan Estuary east of the Xinhe River, Shandan County, Gansu Province, with its reference section being situated in the Kushui Gorge of the Shuidong Gully, Jingyuan County, Gansu Province.
Synonym: （新河组）
Lithology and Thickness
It is composed essentially of yellow-green thick-bedded stratified micro-conglomerate, intercalated with yellow-green sandy shale, with its top part being composed of fine-grained sandstone, intercalated with gritstone and blue-grey siltstone, with a thickness of 229 m.
Relationships and Distribution
Lower contact
Its basal part overlies conformably the Yaojie Fm
Upper contact
No top of it has been found. Regionally, the schematic strat column indicates the next younger unit as Kushuixia Fm
Regional extent
On the reference section, the rocks of the formation are getting finer. Except for its basal part where there are found to occur grey-white conglomerate and pebble-bearing gritstone, its middle and lower parts are composed mainly of an alternating layer of grass-yellow sandstones and sandy shales, with its upper part being composed largely of grey and grey-green shales, intercalated thin-bedded marls, with a total thickness of 611 m. It is in a conformable contact with both the underlying Yaojie Fm and the overlying Kushuixia Fm. It yields plant fossils as represented by Coniopteris tatungensis, C. cf. hymenophylloides and Raphaelia sp.; Chareae fossils as represented by Aclistochara yunnanensis and etc.; “conchostracan” fossils such as Euestheria jingyuanensis; insect fossils such as Karataviella chinensis and Ostracoda fossils as represented by Darwinula sarytirmenensis. The formation is distributed in the Shandan, Yongchang, Wuwei and Jingyuan regions of Gansu Province.
GeoJSON
Fossils
The naming section yields bivalve fossils as represented by Pseudocardinia jeniseica and P. spp.
Age
Depositional setting
Additional Information
Age:
Schematic strat column suggests mid-Middle Jurassic age
Age span:
Beginning stage: Bajocian
Fraction up in beginning stage: 0.5
Beginning date (Ma):
Ending stage: Bathonian
Fraction up in ending stage: 1.0
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information
Compiler
Jingeng Sha (coordinator)