Zelong Gr
Type Locality and Naming
Xainza Co. The Zelong Group was erected by the Regional Geological Survey Team under the Xizang Bureau of Geology and Mineral Resources in 1983. The section for the designation is in Burga of the Xainza County, Xizang (86°15′E; 31°10′N).
Lithology and Thickness
Lower part of the Zelong Group is represented by purple red, dark green and gray green volcanic breccia and andesitic tuff, and gray white and gray volcanic breccia tuff and conglomerate. Upper part is light green, gray purple and gray yellow metamorphosed sandstone interbedded with black shale and mudstone, intercalated with multiple layers of yellow bioclastic calcareous sandstone and gray thin-bedded bioclastic limestone. The formation is in excess of 990 m thick.
Relationships and Distribution
Lower contact
The base of the Group is not observed. [Original Cret Lex entry had said "regionally, it is unconformable and locally disconformable contact with the underlying Shamuluo Fm (J3)", however the Shamuluo Fm type area is much further west (by 4° longitude).
Upper contact
In the Burga and Jieda areas, the top of the formation (quartzite) is conformable below the gray white limestone and marble at the base of the Daguonuma Gr
Regional extent
The present Group is distributed in Xinji-Lazenalong, Zuowa, Qiucuomai-Delai on the east bank of Dangrecuo, Burga, Coqen, and westward to the Wuma and Shiquanhe area of Gerze County. It is persistent in lithology. The Xizang Regional Geological Survey Team called it the Weien Fm (K1) in 1987 in the Wuma-Shiquanhe area, with a few number of marine partings only in the west. Regionally the base of the formation is not observed in the Xainza area of east Xizang, and in the Wuma-Shiquanhe area of Gaize County of west Xizang, the Weien Fm is in unconformable and locally disconformable contact with the underlying Shamuluo Fm (J3). The Zelong Gr is 400 to more than 6200 m in thickness.
GeoJSON
Fossils
In the Burga area, it yields bivalves Cyprina teolluensis, Cyprimeria cf. quadrata, etc.
Age
Depositional setting
Additional Information