Nieniexiongla Fm
Type Locality and Naming
It was named by Mu Enzhi as the Nieniexiongla Group in 1973. The naming section is located in the vicinity of the Nieniexiongla area at the No. 10-11 Maintenance Squad of the Dingri-Nyalam Highway.
Synonym: （聂聂雄拉组）
Lithology and Thickness
Lower part of the formation consists of alternating layers of grey medium-bedded limestones and argillaceous limestones, intercalated with sandy shales, grey-black medium-, and thin-bedded limestones, grey-white medium-, and coarse-grained quartz-sandstones, yellow-green sandy shales, siltstones and poststones (=fine-grained sandstone). Middle part consists of dark-grey thick-bedded limestones, grey-white quartz-sandstones, intercalated with limestones. Upper part consists of alternating layers of dark-grey medium-, and thin-bedded limestones, sandy limestones and quartz-sandstones, intercalated with grey-black and yellow-green shales. It is 1639 m in thickness.
Relationships and Distribution
Lower contact
Its basal part is in a fault contact with the lower Cretaceous Series. Regionally, the next older unit is the Pupuga Fm of earliest Jurassic.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Menkadun Fm
Regional extent
The formation is distributed mainly in the areas of Nieniexiongle, Lalongla Pass, Dingri and Jilong, with a consistent lithology and with a thickness of 600-1500 m.
GeoJSON
Fossils
It yields in the Nieniexiongla region abundant ammonites, bivalves, Brachiopoda and Gastropod fossils. Among the ammonites fossils there are found Witchellia tibetica, W. sayni, Dorsetensia haydeni, D. xizangensis, D. cf. edauardiana, Macrocephalites sp., M. compressus, M. cosmopolitum, Indocephalites spaeroidalis and I. Diadematus; of bivalves there are found Trigonia (T.) brevicostata, T. (T.) cf. brevicostata, Camptonectes les, C. cf. laminatus, Variamussium pumilum, Ostrea (Liostrea) acuminata and Cucullaea cf. egertoniana.
Age
Depositional setting
The formation represents typical littoral and shallow-sea deposits.
Additional Information