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Xixiang Gr
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Xixiang Gr base reconstruction

Xixiang Gr

Period: 
Neoproterozoic

Age Interval: 
Qingbaikouan (Tonian), Qb (41-b)


Province: 
Shaanxi

Type Locality and Naming

Southwest Shaanxi. The Xixiang Gr was named by the Qinling Party of regional Geological Survey, Shaanxi Bureau of Geology in 1960. The naming section is located on east and west sides of the town of Xixiang County, Shaanxi Province.

Synonym: （西乡群）


Lithology and Thickness

The Xixiang Gr consists of a suite of marine terrestrial intermediate basic to acidic volcanic and volcaniclastic rocks. Lower part consists of gray green, purple red dacitic tuff with andesitic and rhyolitic tuff, tuffite and minor andesite, 1000-1500 m thick. Upper part is composed of gray purple basalt, andesite, rhyolite, trachy-andesite and trachyte with purple and variegated volcanic breccia or agglomerate and also with minor red tuffaceous sandstone-conglomerate, tuff, tuffite, sandstone, mudstone and mud-ball tuff, 800 m thick. The maximum thickness is over 2300 m thick.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

It has a faulted contact to the underlying Sanhuashi Fm (Sanhuashi Gr).

Upper contact

The top is conformably overlain by the Sinian System (Jiudaoguai Fm?)

Regional extent

Southwest Shaanxi. The group is mainly distributed in Sunjiahe, Sanlangpu, Dahuigou, Zhulinpo (Majiazhai) near Xixiang County, Shaanxi Province.


GeoJSON

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Fossils


Age 

An isotopic (Rb-Sr) date of 775 Ma was acquired from the metamorphosed rhyolite in the lower part of the group. In addition, another isotopic (whole-rock Rb-Sr) date of 800 Ma is from the plagio-granite of Hannan Complex, which was intrusive into this group. Therefore, the age of the Xixiang Gr is considered as older than 800 Ma and tentatively belongs to the Qingbaikouan. Schematic stratigraphic column puts as spanning Qingbaikouan. For graphic purposes, shown here as upper 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.