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Sujiawan Formation
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Sujiawan Fm base reconstruction

Sujiawan Fm

Period: 
Neoproterozoic

Age Interval: 
Late Nanhuan (late Cryogenian), Nh (51)


Province: 
Anhui

Type Locality and Naming

Central-east Anhui. The Sujiawan Fm was named by Xu Jiawei et al. in 1965 and formally quoted by the Anhui Party of Regional Geological Survey in 1977 (Guidebook of 1 200 000 Scale Regional Geological Map of Nanjing Sheet). The typical section is situated in Sujiawan of Chaohu City, and the reference section is in Luojia'ao of Chuxian County, Anhui Province.

Synonym: （苏家湾组）


Lithology and Thickness

The Sujiawan Fm is a suite of low-grade metamorphic tillite, generally containing a lot of tuffaceous matter. Lower part is composed of gray to greenish gray pebbly sandy phyllite. Middle part consists of milky white metamorphic quartzite and greenish yellow sandy phyllite. Upper part is greenish gray pebbly sandy phyllite and pebbly phyllite, with the top part locally intercalated with two beds of andesite. The pebbly phyllite is characterized by unclear stratification, regular orientation of pebbles with poor roundness and sorting, mostly compressed or elongated, generally 0.2-5 cm in diameter, with the largest of 20-50 cm, which are composed of metamorphic volcanic rock, schist, gneiss, migmatite and phyllite. The Sujiawan Formation is 765 m thick.


Lithology Pattern: 
Glacial till


Relationships and Distribution

Lower contact

It disconformably rests on the underlying Zhougang Fm

Upper contact

It is overlain by the Doushantuo Fm (Ediacaran)

Regional extent

East Anhui. It is dominantly distributed in Sanheji in Quanjiao County to Zhulong in Chuzhou County, Anhui Province.


GeoJSON

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Fossils


Age 

Late Nanhuan (late Cryogenian) on schematic stratigraphic section. Interpretation of the middle part as interglacial (see Additional Information) suggests it spans both of the glacials of the Cryogenian?

Age Span: 

    Beginning stage: 
Cryogenian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
720.00

    Ending stage: 
Cryogenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
635.00

Depositional setting


Depositional pattern:  


Additional Information

) suggests it spans both of the glacials of the Cryogenian?

Age span:

Beginning stage: Cryogenian

Fraction up in beginning stage: 0.0

Beginning date (Ma):

Ending stage: Cryogenian

Fraction up in ending stage: 1.0

Ending date (Ma):

Depositional setting:

Depositional-pattern:

Additional Information

The quartz sandstone and sandy phyllite in the middle part of the Sujiawan Formation is probably a product from the interglacial stage.


Compiler:  

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