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Gucheng Formation
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Gucheng Fm base reconstruction

Gucheng Fm

Period: 
Neoproterozoic

Age Interval: 
Middle Nanhuan (early Cryogenian), Nh （47, 49, 52, 53, 58, 60）


Province: 
Hubei, Guizhou, Hunan, Sichuan, Anhui

Type Locality and Naming

The Gucheng Fm was named by Ma Guogan et al. in 1984. The typical section is located at Gucheng 5.5 km southeast of Gaojiayan, Changyang County, Hubei Province.

Synonym: （古城组） , Its synonyms or coeval formations include the Pingqian Formation in Shennongjia area of west Hubei, the Tiesi'ao Fm in northeast Guizhou and the Dongshanfeng Fm in west Hunan.


Lithology and Thickness

The Gucheng Fm is composed of greenish gray tilly sandy gravel or pelodite, in which the gravels are disorderly and unsystematically arranged, have a great disparity in grain size, and display complex compositions including sandstone, siltstone, granite, vein-rock, marl and other carbonates. The gravels are poorly rounded, generally with striations. The thickness varies from several meters to about ten meters. It has with an unstable thickness from 3 to 17 m.


Lithology Pattern: 
Glacial till


Relationships and Distribution

Lower contact

The Gucheng Fm rests disconformably on the underlying Liantuo Fm

Upper contact

It is overlain by the Datangpo Fm

Regional extent

The Gucheng tillite is mainly distributed in Hunan, Hubei, Sichuan and Guizhou provinces..


GeoJSON

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Fossils

microplants: Trachysphaeridium laminaritum, Stictosphaeridium implexum, Quadratimorpha jugata, Favososphaeridium sp. Anguloplanina rhombica, Laminarites antiquissimus, etc.


Age 

Middle Nanhuan (early Cryogenian); assumed here to span the Sturtian glacial.

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: 
0.7

    Ending date (Ma):  
660.50

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.