Cuojiangding Gr
Type Locality and Naming
The naming section is located near Cuojiangding ~38 km north of the seat of Zhongba County, Tibet. Named by the Tibet Regional Geological Survey Party in 1979.
Lithology and Thickness
Lower and Middle parts consist dominantly of gray and dark gray lithic grit, with bioclastic limestone and sandy shale; Upper part is composed mainly of grayish black shale with sandy marlstone; Top has gray pebbly grit with conglomerate. Its lithology and thickness vary greatly laterally. The total thickness is >575 m.
Relationships and Distribution
Lower contact
Conformable contact with the underlying Cretaceous Qubeiya Fm.
Upper contact
The top of this group is not defined.
Regional extent
It is exposed in the Zhongba-Geer area north of the Yarlung Zangbo River and distributed in an E-W direction. Rocks of this group are a sequence of low-maturity clastic rocks with carbonate rocks. Representing a stagnant sea gulf with a reducing environment, this group belongs to regressive facies or littoral molasses deposits in the fore-arc basin on the southern margin of the Gangdise.
GeoJSON
Fossils
The group contains abundant fossils, including foraminifera, large-sized bivalves etc. The middle and lower parts yield the foraminifera Ronikothalia nuttalli, Miscellanea cf. meandrina and Operculina subsalsa; in the upper part there appear the foraminifera Nummulites, Assilina and Fasciolites. No fossils have been found in grit with conglomerate at the top.
Age
Depositional setting
Rocks of this group is a sequence of low-maturity clastic rocks with carbonate rocks. Representing a stagnant sea gulf reducing environment, this group belongs to regressive facies or littoral molasses deposits in the fore-arc basin on the southern margin of the Gangdise.
Additional Information