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Zhagu Formation
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Zhagu Fm base reconstruction

Zhagu Fm

Period: 
Neoproterozoic

Age Interval: 
late Qingbaikouan (middle Tonian), Qb (44)


Province: 
Sichuan

Type Locality and Naming

Southernmost Sichuan. The Zhagu Fm was named by Yu Zhongcai in 1963. The naming section is in Xinjietian to Xinping, Yanbian County, Sichuan Province. Upper formation in the Yanbian Gr.

Synonym: （则姑组)


Lithology and Thickness

The formation is dominated by sericite slate. Base is composed of metamorphosed tuffaceous conglomerate and sandy conglomerate lenses. The pebbles in the conglomerate are mostly of volcanic lava. Lower part is often intercalated with carbonaceous slate and fine-grained meta-sandstone, siltstone. Upper part is mainly interbedded dolomitic limestone and dolomitic slate. Locally, the dolomitic limestone is in brecciform.


Lithology Pattern: 
Shallow-marine marl


Relationships and Distribution

Lower contact

It is in disconformable contact with underlying Xiaoping Fm (upper-middle formation in Yanbian Gr).

Upper contact

The top is unconformable with the overlying Lieguliu Fm.

Regional extent

Southernmost Sichuan. It is developed in Yanbian County, Sichuan Province.


GeoJSON

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Fossils


Age 

late Qingbaikouan (middle Tonian)

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.6

    Beginning date (Ma): 
832.00

    Ending stage: 
Tonian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
776.00

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Extracts from The Neoproterozoic Erathem (chapter in Stratigraphic Lexicon of China, draft of 2022) by Gao Linzhi, Ding Xiaozhong, Zhang Chuanheng, Zhang Heng.