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Yingan Formation

Yingan Fm

Period: 
Ordovician

Age Interval: 
Katian, (18)


Province: 
Xinjiang

Type Locality and Naming

The type section is at Village Yingan in Kalpin, Xinjiang. The Yingan Fm was named by Zhan Shigao in 1964.

Synonym: (印干组）


Lithology and Thickness

The Yingan Fm is composed of black, dark gray silty shale intercalated with calcilutite. At Dawangou in Yingan, Keping, the Yingan Fm is 35 m thick, and in Keping (Kalpin) County it is 34-90 m thick.


Lithology Pattern: 
Pelagic marl


Relationships and Distribution

Lower contact

The Yingan Fm rests conformably on the argillaceous limestone of the Qilang Fm

Upper contact

The formation is truncated by an erosive exposure surface of mid-Katian, then preserved deposition resumed in the latest Ordovician or earliest Silurian. It is paraconformably overlain by the Kalpintag Fm of early Silurian. In Keping County, the upper boundary not higher than the upper boundary of the Caradoc.

Regional extent

In Keping County.


GeoJSON

null

Fossils

Qiao Xindong (1986) considered the Yingan Fm to be Late Caradocian to Early Ashgillian in age. It yields graptolites of C. (Diplacanthograptus) spiniferus assemblage, trilobite Ampyxinella ovata and chitinozoan Tanuchitina bergstromi.


Age 

Katian. Zhou Zhiyi et al. (1990) restudied the type section, and suggested that the Yingan Fm includes only one graptolite zone, i.e. the C. (Diplacanthograptus) spiniferus zone of mid-Katian.

Age Span: 

    Beginning stage: 
Katian

    Fraction up in beginning stage: 
0.4

    Beginning date (Ma): 
449.73

    Ending stage: 
Katian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
451.24

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Jianpo Wang and Xiaofeng Wang