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Longbeixi Formation
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Longbeixi Fm base reconstruction

Longbeixi Fm

Period: 
Neoproterozoic

Age Interval: 
Late Nanhuan (late Cryogenian) Nh (69)


Province: 
Fujian

Type Locality and Naming

North-central Fujian. The Longbeixi Fm was named by the Fujian Institute of Geology in 1961 and formally quoted by the Party of Regional Geological Survey, Fujian Bureau of Geology in 1974. The typical section is situated in Longbeixi village 35 km southeast of Jian'ou City in Fujian Province.

Synonym: （龙北溪组）


Lithology and Thickness

Lower part of the Longbeixi Fm is composed of quartzite intercalated with marble, dolomite, biotite-quartz schist and epidote- plagioclase leptite, occasionally bearing thin-bedded phosphorite. Middle part consists of muscovite-quartz schist, two-mica schist intercalated with quartzite, with sedimentary rhythm. Upper part consists of greenschist including epidote, actinolite, hornblende, albite, chlorite etc, and commonly intercalated with quartzite, marble and phosphorite. From north to south, its grain size is decreases, the calcareous and siliceous sediments increase, and its thickness decreases also. The total thickness is more than 2230 m.


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

The contact relationship with the underlying Dikou Fm is not clear.

Upper contact

The Longbeixi Fm is conformably overlain by other units. [But schematic stratigraphic column does not show these.]

Regional extent

North-central Fujian.


GeoJSON

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Fossils

The Longbeixi Formation yields microplants Polyedrosphaeridium sp., Brocholaminaria sp., Leiopsophosphaera sp., Octaedrixium sp., Taeniatum sp.


Age 

Late Nanhuan (late Cryogenian)

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


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.