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Jijiu Formation

Jijiu Fm

Period: 
Silurian

Age Interval: 
the Ludlow to Pridoli of Silurian (S3-4), (36)


Province: 
Xizang (Tibet)

Type Locality and Naming

It was named by Yang Zengrong in 1985. The type section is on the ridge, 2 km west of Yali Village, Zhangdong Township, Nyalam County, the Xizang Zizhiqu.

Synonym: (极久组)


Lithology and Thickness

The formation, 16 m in thickness, consists of dark gray medium-to-thin-bedded pelite.


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

It conformably rests onto the underlying Pulu Fm of the Wenlock Epoch

Upper contact

It conformably rests below the overlying Liangquan Fm of mid-Early Devonian

Regional extent

The formation is merely distributed in the area of Yali Village, Nyalam County with very minor changes in lithology, facies and biota.


GeoJSON

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Fossils

It yields abundant fossils like cephalopods Kopanioceras dorsetum, K. jucundum, K. capax; conodonts Polygnathoides siluricus, Ancoradella ploeckensis, Kockella variabilis, Ozarkodina steinhurnensis eosteinhornensis etc.


Age 

The "conformably rests below the overlying Liangquan Fm of mid-Early Devonian" implies extends to the base of Pragian based on age assignment of that formation in Devonian lexicon entry.

Age Span: 

    Beginning stage: 
Gorstian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
426.74

    Ending stage: 
Pragian

    Fraction up in the ending stage: 
0.0

    Ending date (Ma):  
412.40

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wang Chuanshang and Wang Xiaofeng