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Bulong Formation
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Bulong Fm base reconstruction

Bulong Fm

Period: 
Silurian

Age Interval: 
Llandovery of Silurian (S1), (11)


Province: 
Xinjiang

Type Locality and Naming

It was nominated by the Joint Stratigraphical Team between the Xinjiang Party of Regional Geological Survey and the Chinese Academy of Geological Sciences in 1973 and published by Hou Hongfei et al. (1979). The type section is located on both sides of Bulonggor, southeast of the Hoboksar Mongol Autonomous County in the Xinjiang Uygur Zizhiqu. Coordinate: 86°05′55″E, 46°43′20″N.

Synonym: (布龙组)


Lithology and Thickness

It consists of yellow green tuffaceous siltstone, silty shale intercalated with a few calcareous tuffaceous siltstone and siliceous siltstone; the base is greyish-black banded chert and siliceous siltstone. It is 190 m in thickness and can be observed so far merely in the type section area.


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

It is conformable with the underlying Bulongguor Fm of late Ordovician.

Upper contact

The formation is unconformably overlain by the Hargawu Fm of late Carbonaceous. Next younger regional unit is the Sharbur Fm of middle Silurian

Regional extent


GeoJSON

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Fossils

It is rich in graptolite, i.e., Streptograptus cf. becki, S. cf. runicinatus, Monograptus sedgwickii, M. ex gr. acus, Pristiograptus ex gr. concinnus.


Age 

The Llandovery age can be confirmed by the graptolite fossils. [Ordovician column suggests this Bolong Fm begins in mid-Hirnantian.]

Age Span: 

    Beginning stage: 
Hirnantian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
444.14

    Ending stage: 
Sheinwoodian

    Fraction up in the ending stage: 
0.0

    Ending date (Ma):  
432.93

Depositional setting


Depositional pattern:  


Additional Information

Both Su Y Z (in Lin B Y et al., 1988) and Zhang L C et al. (1999) claimed that the formation is overlain by the Hargawu Fm of late Carbonaceous. The authors accepted the idea generally. However, due to the formation is confined only in the type section area, the authors composited the Bulong Fm with the Sharbur Fm and other overlying formations to represent the Silurian succession of West Junggar Area.


Compiler:  

Wang Chuanshang and Wang Xiaofeng