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Yujiagou Formation
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Yujiagou Fm base reconstruction

Yujiagou Fm

Period: 
Neoproterozoic

Age Interval: 
early-Early Qingbaikouan (earliest Tonian), Qb (52, 53, 56)


Province: 
Guizhou

Type Locality and Naming

East Guizhou. The Yujiagou Fm was named by the Party of Regional Geological Survey (No. 108 Party), Guizhou Bureau of Geology in 1974. The named section is in Yujiagou, Yinjiang County, northwest of Fanjing Mountain, Guizhou Province. Lower formation in the Fanjingshan Gr.

Synonym: （余家沟组）, Yujia Fm


Lithology and Thickness

The formation is composed of blasto-siltstone, fine sandstone, sericite phyllite, slate and metamorphosed basic lava. Lower part is dominated by dark-grey and grey blasto-siltstone sandwiched with metamorphosed conglomerate, phyllite and phyllitic slate. Upper part is greyish and grey-white slate intercalated with metamorphosed diabase. The thickness varies from 609 m to over 1464 m.

[Figure: The stratigraphic column of the Fanjingshan Gr (the group is about 1000 m thick). a. Pillow lava of the Huixiangping Fm.; b. The boundary between the underlying Fanjingshan Gr and the Furongba Fm (= lower Jialu Fm?) which is the basal formation of the Xiajiang Gr.]

[Figure: Metamorphic sandstone and tuff of the Yujiagou Fm of the Fanjingshan Gr. a-Conglomerate between metamorphic sandstones; b-Cross bedding in the Yujiagou Fm; c,d-Tuff]


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

It contacts conformably with the underlying Taojinhe Fm

Upper contact

It contacts conformably with the overlying Xiaojiahe Fm

Regional extent

East Guizhou. It only developed in northwest of Fanjing Mountain, Guizhou Province.


GeoJSON

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Fossils


Age 

Zircons in the Yujiagou Formation are dated at 851-845 Ma by IC-P-MAS U-Pb (Wang Min et al., 2012). early-Early Qingbaikouan (earliest Tonian) – the seven formations of the Fanjingshan Gr spanning the early Qingbaikouan (early Tonian) are given semi-equal durations.

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.05

    Beginning date (Ma): 
986.00

    Ending stage: 
Tonian

    Fraction up in the ending stage: 
0.1

    Ending date (Ma):  
972.00

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.