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Mesoproterozoic

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Zegu Formation

Zegu Fm

Period: 
Mesoproterozoic

Age Interval: 
Xishanian-Yuxian (Ectasian-Stenian) Xs-Yx (34)


Province: 
Sichuan

Type Locality and Naming

Mid-South Sichuan. The Zegu Fm was named by the Southwest Geological Institute, Ministry of Geology in 1965. The naming section is in Xiaoshengou, Xide County, Sichuan Province.

Synonym: （乍古组）


Lithology and Thickness

Lower part of the formation is composed of meta-volcanic conglomerate, meta-rhyolite, tuffaceous sandstone, tuff and phyllite. The volcanic rock often facially transitions into quartz sericite phyllite and meta-siltstone, occasionally accompanied with marble lenses. The thickness varies from 234 to 707 m in lower part. Upper part consists of meta-rhyolite, tuff and dacite, which may facially transition into sericite phyllite, silty phyllite with marble lenses. The thickness varies from 218 m to 451 m in upper part.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

It contacts with underlying Shengou Fm with a conformity or disconformity.

Upper contact

The top is conformably overlain by the Chaowanping Fm.

Regional extent

Mid-South Sichuan. The formation is distributed mainly in Zegu, Shengou, Dongshansi, Xide County and Dading Mountain, Mianning County, Sichuan Province.


GeoJSON

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Fossils


Age 

The schematic stratigraphic column places Dengxiangying Gr as spanning Xishanian-Yuxian (Ectasian-Stenian), and each of its 5 formations are given equal spans for graphics.

Age Span: 

    Beginning stage: 
Ectasian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
1,240.00

    Ending stage: 
Stenian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
1,160.00

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

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