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Muzuo Formation
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Muzuo Fm base reconstruction

Muzuo Fm

Period: 
Neoproterozoic

Age Interval: 
Nanhuan (Cryogenian), Nh (40)


Province: 
Sichuan

Type Locality and Naming

Sichuan south of Gansu. The Muzuo Fm was named by the No. 2 Sichuan Party of Regional Geological Survey in 1977 (on the Guidebook of 1: 200 000 Scale of Geological Map of Pingwu Sheet) and formally published on Regional Geology of Sichuan Province in 1991. The typical section is situated in Muzuo in Pingwu County, Sichuan Province.

Synonym:


Lithology and Thickness

The Muzuo Fm is composed of thick-bedded massive pebbly meta-sandstone and meta-conglomerate. With a variable lithology along the strike, it can change into pebbly phyllite (pebbly mudstone) intercalated with pebbly feldspathic greywacke and lenses of dolomite. Locally with an increase in pyroclastics, it changes into tuffaceous conglomerate, pebbly sandstone, sericite chlorite- schist and sericite chlorite tuffite intercalated with lenses of limestone, yielding microplants. Total thickness varies from 0 to 1250 m. See Depos. Setting below.


Lithology Pattern: 
Glacial till


Relationships and Distribution

Lower contact

It rests disconformably or unconformably on the underlying Bikou Gr (Yinping Fm)

Upper contact

It is disconformably or unconformably overlain by the Wugongkou Fm of early Ediacaran

Regional extent

Sichuan south of Gansu.


GeoJSON

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Fossils


Age 

Nanhuan (Cryogenian)

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
776.00

    Ending stage: 
Cryogenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
635.00

Depositional setting

It is considered to belong to the glaciomarine clastic formation by some researchers (such as Yin Jicheng et al., 1993).


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.