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Xainza Formation

Xainza Fm


Period: 
Ordovician

Age Interval: 
Katian-Hirnantian, (58)


Province: 
Xizang (Tibet)

Type Locality and Naming

The type section is along the ridge at the right side of the Bango-Xainza Highways, between Gangmusang and Mendeema, 10 km south of Yougzhuzangbu Bridge in Xainza County, Xizang. The Xainza Fm was named by Ni Yunan et al. in 1981.

Synonym: (申扎组) , Shenzha Fm (spelling)


Lithology and Thickness

The formation is composed of dark gray marl and earthy-yellow calcareous mudstone. In the type area, the Xainza Fm is 8.7 m thick.


Lithology Pattern: 
Pelagic marl


Relationships and Distribution

Lower contact

It rests conformably on the nodular chert limestone at the top of the Gangmusang Fm

Upper contact

It is conformably overlain by the Lower Dewuka Fm (Dewukaxia Fm) of Llandovery age.

Regional extent

Only in the type area see this formation.


GeoJSON

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Fossils

This stratigraphic unit yields graptolites Glyptograptus ? cf. persculptus, Normalograptus extraordinarius, N. bohemicus and brachiopods Hirnantia, Kinnella, Cliftonia, Paromalomena.


Age 

Katian-Hirnantian.

Age Span: 

    Beginning stage: 
Katian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
447.47

    Ending stage: 
Hirnantian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
443.07

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Jianpo Wang and Xiaofeng Wang