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Yijianfang Formation

Yijianfang Fm


Period: 
Ordovician

Age Interval: 
Darriwilian, (19)


Province: 
Xinjiang

Type Locality and Naming

The type section is at Yijianfang to Tangwangcheng (40°N, 78°30'E) in Sanchakou, Bachu County, Xinjiang. The Yijianfang Fm was named by Zhou Zhiyi et al.in 1990.

Synonym:


Lithology and Thickness

The Formation is composed of calcirudite, calcarenite and limestone. The light gray massive limestone bearing Receptaculites represents a shallow biohermal facies. In the type area, the Yijianfang Fm is 54 m thick.


Lithology Pattern: 
Reef limestone


Relationships and Distribution

Lower contact

The Formation rests conformably on the siliceous banded calcirudite at the top of the Yingshan Fm

Upper contact

It is conformably overlain by the thick-bedded sandy bio-calcarenite bearing glauconite at the base of the Tumxuk Fm.

Regional extent

The Yijianfang Fm is exposed in Tangwangcheng to Yijianfang east of Sanchakou.


GeoJSON

null

Fossils

This stratigraphic unit yields nautiloid Protocycloceras wangi.


Age 

Darriwilian.

Age Span: 

    Beginning stage: 
Darriwilian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
469.42

    Ending stage: 
Sandbian

    Fraction up in the ending stage: 
0.0

    Ending date (Ma):  
458.18

Depositional setting

It represents a shallow biohermal facies.


Depositional pattern:  


Additional Information


Compiler:  

Jianpo Wang and Xiaofeng Wang