Zuoyun Fm
Type Locality and Naming
S. Marita established the Zuoyun series in 1944. The type locality is in Zuoyun of Shanxi. The reference section is from Jiankoushan to Hangeda about 4 km southeast of the Zuoyun County, Shanxi.
Lithology and Thickness
The Zuoyun Formation is represented by purple gray conglomerate and red mudstone with gray green mudstone, which is divided in ascending order into three members. First member is dominated by light gray conglomerate with red conglomeratic limestone and mudstone. Second member is red conglomerate, sandy mudstone and mudstone interbeds of different thicknesses, with two layers of gray green mudstone. Third member is red and gray green mudstone and gray white mudstone lumps with sandy conglomerate and conglomerate. It is 208 m thick.
Relationships and Distribution
Lower contact
Its base is a major disconformable contact marked by light gray conglomerate that is distinguished from gray white sandstone of the underlying Jurassic Yungang Fm in the type section. Regionally, the present formation shows an angular discordance on the strata of different ages; with the Wangjiagou Fm being the youngest (Hauterivian? in age)
Upper contact
Its top is a disconformable contact marked by red mudstone that is separated from dark purple red gravel-bearing sandy mudstone of the overlying Zhumabao Fm (Zhumapu Fm).
Regional extent
The present formation is distributed in Zuoyun, Youyu, Yanggao and Hunyuan counties and Datong City of Shanxi. It varies considerably both in lithology and thickness. In Yuanbaozi of the Youyu County and Jiugaoshan of the Datong City, relatively thick crystalline limestone is developed with a thickness of up to 20 m. But in Jiankoushan and Madaotou of the southeastern Zuoyun County, the first member of the formation is dominated by conglomerate, occasionally with conglomeratic limestone. The second member is about 200 m thick in southeast Zuoyun, and 50-100 m in southwest Zuoyun, south Youyu and Jiugaoshan of Datong city.
GeoJSON
Fossils
The formation yields bivalves Lepesthes sp.; estheria Yanjiestheria sp.; ostracods Ziziphocypris costata, Timiriasevia princepalis, Cypridea tera, Rhinocypris tugurigensis; Charophytes Euaelistochara mundula, Aclistochara bransoni, Mesochara syminetrica, Pseudolatochara rhombia; sporopollen grains such as the Cicatricosisporites-Crybelosporites-Tricolpites assemblage.
Age
Depositional setting
It belongs to fluvial-lacustrine deposition
Additional Information