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Jiayuan Formation
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Jiayuan Fm base reconstruction

Jiayuan Fm

Period: 
Neoproterozoic

Age Interval: 
early Sinian (early Ediacaran), Z (27, 28)


Province: 
Jiangsu

Type Locality and Naming

North Anhui – Jiangsu border region. The Jiayuan Fm was named by the Jiangsu and Anhui Parties of Regional Geological Survey in 1976 and was formally published on the Guidebook of 1: 200 000 Scale Geological Map of Xuzhou in 1978. The typical section is situated in Jiayuan of Zhancheng Township of Pixian County, Jiangsu Province.

Synonym: (贾园组)


Lithology and Thickness

The Jiayuan Fm is dominated by gray and bluish gray thin- to medium-bedded calcarenite, micaceous sandy marl with wavy oblique beddings, intercalated with calcareous fine-grained quartzose sandstone, siltstone, greenish yellow shale bearing lenses of stromatolite limestone at top. With an unstable thickness, it is only 32 m in Wangbu, and more than 690 m in Zhancheng of Pixian.

[Figure: Outcrop photos of Jiayuan Fm]


Lithology Pattern: 
Sandy limestone


Relationships and Distribution

Lower contact

The base rests conformably on the underlying Sishilichangshan Fm (Jushan Fm). The type section is short of the lowermost sequence, so this basal relationship with the underlying strata is based on the Jushan section in Wangbu, Tongshan County.

Upper contact

The top is overlapped by Cambrian in the Xuzhou to Jiawang area.

Regional extent

North Anhui – Jiangsu border region. The Jiayuan Fm is restricted to Tongshan, Pixian and Suining counties in Jiangsu Province.


GeoJSON

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Fossils

The Jiayuan Formation yields stromatolites: Baicalia f., and Microplants: Leiopsophosphaera minor, Trachysphaeridium simplex, T. cultum, Lophosphaeridium ichangense, Micrhystridium sp., Quadratimorpha sp. etc.


Age 

See discussion on the age of Liulaobei Fm, which is conformable below the underlying Sishilichangshan Fm, of which its upper member is apparently assigned to Sinian. Therefore, even the schematic stratigraphic column has indicated a "Cryogenian" placement, it is placed in the lower Ediacaran for this graphic column. Therefore, lower (2 of 10) in a succession of eight formations spanning early through middle Sinian (early through middle Ediacaran) formations according to assigned "Z" code and schematic stratigraphic column.

Age Span: 

    Beginning stage: 
Ediacaran

    Fraction up in beginning stage: 
0.1

    Beginning date (Ma): 
625.38

    Ending stage: 
Ediacaran

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
615.76

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.