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Xiafang Formation
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Xiafang Fm base reconstruction

Xiafang Fm

Period: 
Neoproterozoic

Age Interval: 
Late Nanhuan (late Cryogenian), Nh (64)


Province: 
Jiangxi

Type Locality and Naming

West-central Jiangxi. The Xiafang Fm was named by the Jiangxi Party of Regional Geological Survey in 1962 and was quoted in the report of regional geological survey of 1: 200 000 Scale of the Xinyu sheet. The naming section is located at Xibiankeng, Xiafang, Xinyu County, Jiangxi Province.

Synonym: （下坊组）


Lithology and Thickness

In the naming section, the Xiafang Fm consists of gray-green, dark gray and black gray sericite phyllite, silty phyllite and carbonaceous sericite phyllite with one or two beds of banded magnetite quartzite. Some meta-basalt can be found below the ore bed. Thickness is about 330 m thick.


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

It is disconformably with the underlying Shanshi Fm

Upper contact

It is conformable overlain by the Laohutang Fm

Regional extent

Jiangxi Province.


GeoJSON

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Fossils

Microplants found in carbonaceous slate at top of the ore bed include Brocholaminaria, Laminarites, etc.


Age 

Late Nanhuan (late Cryogenian) on schematic stratigraphic chart.

Age Span: 

    Beginning stage: 
Cryogenian

    Fraction up in beginning stage: 
0.4

    Beginning date (Ma): 
686.00

    Ending stage: 
Cryogenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
635.00

Depositional setting

The lithology of the formation changes considerably. In Songgujia, Fenyi County, on the west slide of the naming section, the bottom of the formation has dark gray, brown-gray tuffaceous conglomerate and tuffaceous pebbly phyllite, tens of meters thick (Gujia conglomerate). To the south of Suichuan-Xingguo, it changes to blasto-coarse clastic rocks or sandy conglomerate without iron ore and carbonaceous rocks.


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.