Rigana Fm
Type Locality and Naming
Himalayan South Belt. The Rigana Formation was erected by Liu Guifang and Wang Sien in 1987. The section for the designation is in Xishan of the Gucuo Village of Sidaoban along the China-Nepal Highway from Tingri to Nyalam of Xizang. The “Rigana Formation” is a upper-middle part of the Gucuocun Gr (see the item of Gucuocun Gr).
Synonym: “Rigana Formation” (in quote marks)
Lithology and Thickness
The Lower and Middle parts of the Rigana Formation are built up by black, gray green and yellow green shale with brown yellow sandstone and gray mudstone richly bearing ferruginous nodules, with yellow green moderately thick-bedded fine sandstone at the base, while the Upper part is built up by gray, grayish green and black mudstone and shale and yellowish green fine sandstone with marl. The Rigana Formation is 530 m thick.
Relationships and Distribution
Lower contact
The base of the formation lies conformably on the underlying Pandingsi Fm.
Upper contact
Regional extent
The present formation is mainly distributed in the Gucuo area. It is persistent in lithology.
GeoJSON
Fossils
In the Gucuo area, it yields abundant ammonites Pulchellia comprassissima, P. cf. hettneri, P. cf. rolloti, P. veleziensis, P. cuachebnsis, Karstenea cf. collinsi, Aconeceras flexuoum, A. lecontei, Cleoniceras xizangense, etc.
Age
Depositional setting
It belongs to sea trough marginal- external continental shelf deposition.
Additional Information