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Shibandun Formation
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Shibandun Fm base reconstruction

Shibandun Fm

Period: 
Neoproterozoic

Age Interval: 
Early Nanhuan (late Tonian-early Cryogenian), Nh (14)


Province: 
Gansu

Type Locality and Naming

Middle Qilian (north-central Gansu-Qinghai border region). The Shibandun Fm was named by Qian Jiagi et al. in 1978. The typical section is situated in Shibandun in middle Qilian Mountains, Gansu Province. Lower formation of the Duoruonuor Gr.

Synonym: （石板墩组）


Lithology and Thickness

The Shibandun Fm is subdivided into three lithologic parts. Lower part is greenish gray to gray dacitic breccia-tuff, dacitic tuffitic breccia and metamorphic dacitic-tuff. Middle part consists of dark gray to black medium-bedded chert, siliceous slate, sericite silty slate, greywacke intercalated with intermediate to basic tuff-breccia and tuffite. Upper part is composed of greenish gray tuffaceous, calcareous chlorite schist, tuffaceous epidote schist and chlorite-sericite phyllite, intercalated with intermediate to basic metamorphic tuff. The top part is sandy slate and pebbly sandstone. Eastward to Chaganburgas area, the facies changes into a normal marine detrital rock. Thickness varies from 1024 to 1400 m


Lithology Pattern: 
Volcanic ash


Relationships and Distribution

Lower contact

It overlies unconformably the underlying Gongcha Gr (Qingbaikouan System).

Upper contact

It is conformably overlain by the Bianmagou Fm

Regional extent

Middle Qilian Mountains, Gansu Province. The Shibandun Fm is mainly distributed in Duoruonuor, Shibandun, Chaganburgas and Kaoksai areas.


GeoJSON

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Fossils

The formation yields abundant microplants: Asperatopsophosphaera umishanensis, A. bacca, A. partialis, A. cf. baulensesis, Cornutosphaera polycornuta, Leiofusa cf. bicornuta, Dictyosphaera macroreticulata, Monotrematosphaeridium asperum, polyporata obsoleta, Lophosphaeridium gibberosum, Pseudozonosphaera uerrucosa, P. asperella, Trachysphaeridium planum, T. simplex, T. stipticum, T. hyalinum, T. minor, Palaemorpha figurata etc.


Age 

Early Nanhuan (late Tonian-early Cryogenian) on schematic stratigraphic column.

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: 
0.3

    Ending date (Ma):  
694.50

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.