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Suonahu Formation

Suonahu Fm


Period: 
Paleogene

Age Interval: 
Late Eocene to Early Oligocene, E2-E3, (8e)


Province: 
Xizang (Tibet), Qinghai

Type Locality and Naming

The holostratotype is the Suonahu East Section (N33°54′00″, E86°43′00″), Shuanghu, Xizang Autonomous Region (Tibet). Named and measured by the Regional Geological Survey Brigade of Tibet in 1986.

Synonyms: The Suonahu Formation is synonymous with the Maerguochaka Gr, the Shuanghu Gr, the Qiaoertianshan Gr, the Dingqing Gr, and the Zongbai Gr.


Lithology and Thickness

The Suonahu Formation consists of red brick-red, earth-red or bright-red mudstone, clayey siltstone, sandstone, coarse sandstone, gravelly sandstone and conglomerate, interbedded with multi-layer gypsum horizons which is available for mining. The thickness ranges from 530-4300 m.


Lithology Pattern: 
Gypsiferous claystone


Relationships and Distribution

Lower contact

The Suonahu Formation unconformably overlies the Kangtuo Fm, the Yanshiping Gr or other Mesozoic strata.

Upper contact

The Suonahu Formation is unconformably overlain by the Shipingding Fm (synonymous with Chabaoma Fm in Qinghai province).

Regional extent

Ngari Prefecture and Naqu Prefecture, Tibet Autonomous Region. Haixi Mongolian and Tibetan Autonomous Prefecture, Qinghai Province.


GeoJSON

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Fossils

The Suonahu Formation contains fossils of freshwater gastropods (Lymnae, Gyraulus) and bivalves.


Age 

Late Eocene to Early Oligocene

Age Span: 

    Beginning stage: 
Bartonian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
41.03

    Ending stage: 
Rupelian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
27.29

Depositional setting

Fluvial-lacustrine deposit facies.


Depositional pattern:  

Additional Information


Compiler:  

Tao Deng, Sukuan Hou, J.Z. Qigao, Q. Li, Q.Q. Shi, B.Y. Sun, S.Q. Wang, F.X. Wu