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Muyangtan Formation
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Muyangtan Fm base reconstruction

Muyangtan Fm

Period: 
Neoproterozoic

Age Interval: 
late-middle Qingbaikous (middle Tonian), Qb （7）


Province: 
Xinjiang

Type Locality and Naming

Aksu-Kalpin region. The Muyangtan Fm was named by Gao Zhenjia et al. in 1986 and formally published by Lu Songnian et al. in 1990. The typical section is situated in Muyangtan 500 m southwest of Yourmeinak village, Wushi County and the key reference section is north of Sugaitbulak, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region). Upper-middle formation of Qiaoenbulak Gr.

Synonym: （牧羊滩组）


Lithology and Thickness

The Muyangtan Fm is dominantly composed of greenish gray and dark gray laminated calcareous siltstone interbedded with thin-bedded fine-grained sandstone bearing micro flat-bedded or cross-bedded sedimentary structures. The sandstone and siltstone constitute obvious rhythmites. The thickness varies from 107 to 448 m.


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

With a persistent lithology, the base rests conformably on the underlying Donggiaoenbulak Fm

Upper contact

The top is disconformably or locally unconformably overlain by the Dongwu Fm

Regional extent

Aksu-Kalpin region. The Muyangtan Formation is dominantly distributed in south Qiaoenbulak, Yuormeinak, Fangshan, Qigebulak, Sugaitbulak and Yurtusi Mountain area in Wushi County of Xinjiang.


GeoJSON

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Fossils

This formation yields abundant microplants (identified by Peng Changwen and Gao Linzhi), dominated by Trachysphaeridium minor, T. cultum, Trematosphaeridium holtedahlii, Leiopsophosphaera kepingense, L. incrassata, L. aperta, Pseudozonosphaera sp., Taeniatum cf. simplex, T. crassum, Polyporata obsoleta etc. and trace fossils Chondrites von. sternbeng etc.


Age 

There are two opinions about the age of the Muyangtan Formation, one considers it belongs to the Late Qingbaikouan, and the other to the Nanhuan. Strat column schematically shows as upper-middle quarter of Qingbaikous (middle Tonian), used here for graphics.

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.3

    Beginning date (Ma): 
916.00

    Ending stage: 
Tonian

    Fraction up in the ending stage: 
0.4

    Ending date (Ma):  
888.00

Depositional setting

It is interpreted as clastic gravity flow deposits derived from the marginal subaqueous fan.


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.