Gyiseng Fm
Type Locality and Naming
The type section is located from Diyag to Gyiseng, northwest of Zanda County, Tibet. It was named by Guo Tieying et al. in 1991.
Synonym: Jiesheng Fm (spelling)
Lithology and Thickness
Sandstone and Claystone. Dominated by dark-colored clastic rocks, intercalated with slate and calcareous slate. Lithological analysis shows that crossed beds, ripple marks and traces such as burrows are occasionally found in the fine-grained quartzose sandstone, gray-yellow siltstone, black slate, calcareous shale and quartzose sandstone, belonging to a neritic subtidal environment. The shales, besides containing brachiopods and gastropods, bryozoans are concentrated into beds, and often associated with black shales in a gulf environment where surface water bodies are blocked. Thickness >300 m.
Relationships and Distribution
Lower contact
Uncertain: Bottom unexposed. Regionally, the next older unit is the Shangdiyag Fm
Upper contact
Disconformable contact with the overlying Lower Permian Mangzongrongzhong Fm of Lower Permian, and locally in unconformable contact. Regionally, the next younger unit is the Dingbo Gr of Upper Carboniferous
Regional extent
Distributed around the stud farm of the Ngari Prefecture
GeoJSON
Fossils
Containing abundant Bryozoans of Fenestell cf. plebei; Brachiopods Syringothyris sp., Hemiplethorhynchus kashmirensis and Productus sp.; gastropods Straparollus dichysii and Bellerophon sp.
Age
Depositional setting
It is interpreted as a neritic subtidal environment
Additional Information