Sangzugang Fm
Type Locality and Naming
South Lhasa Block - Xigaze forearc Basin. The Sangzugang Formation was erected by Wu Haoruo, Wang Dongan and Wang Liancheng in 1977. The section for the designation is 14 km north of Xiabujiding of the Sa’gya County, Xizang. The reference section is from Dazhuka to Sinisai of the Xigaze City, Xizang.
Lithology and Thickness
Lower part of the Sangzugang Formation is built up by gray black shale with calcareous nodules and marl lenses which can change to thick-bedded conglomerate. Middle part is dark gray thick-bedded limestone with bioclastic limestone, which may change into gray calcareous shale with marl lenses. Upper part is gray sandy shale with sandstone lenses, which may change into lithic sandstone, and breccia lithic sandstone with fine sandstone. The Sangzugang Formation is from 158 to 907 m thick.
Relationships and Distribution
Lower contact
The base of the formation marked by gray shale lies conformably on the underlying Qiablin Fm marked by purple red siltstone.
Upper contact
Regionally, it is in conformable contact with the overlying strata.
Regional extent
The present formation mainly occurs in Xishan and Dazhuka of Xigaze and the Sangzugang Village of the Sa’gya County. It is persistent in lithology and ranges from 158 to 907 m in thickness.
GeoJSON
Fossils
In the Xigaze-Dazhuka area, it yields foraminifera Orbitolina concava qatarica, O. aperta, O. conica, O. scutum, Daxia cenomana, etc.; bivalves Bournonia sp., Eoradiolites sp., etc.; gastropods Pseudomaura cf. bulbiformis, Plesioptygmatis sp., Pterodonta sp., Pleurotomaria sp., etc. According to the Orbitolinid fauna, the formation is of Aptian to early Albian age.
Age
Depositional setting
Additional Information