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Beisainartag Formation
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Beisainartag Fm base reconstruction

Beisainartag Fm

Period: 
Neoproterozoic

Age Interval: 
middle QIngbaikouan (middle Tonian). Qb (9)


Province: 
Xinjiang

Type Locality and Naming

Kuruktag region. The Beisainartag Fm was named by Zhu Chengshun et al. in 1957 and was formally published by Gao Zhenjia in 1980. The typical section is located in Xingertag of middle Kuruktag northeast of Yuli County and the important reference section is situated in the south slope of Pargangtag south of Shanshan County, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region). Upper formation of the Pargangtag Gr.

Synonym: （北塞纳尔塔格组）


Lithology and Thickness

Lower and middle parts are dominated by stromatolite-reef crystalline limestone bearing, dolomite intercalated with minor siltstone. The stromatolite reefs in the lower part are commonly extensive and preserved as stratiform bodies. Upper part is composed of gray to light gray crystalline limestone, marble, crystalline dolomite or micritic limestone and stromatolite-reef limestone with oncolite marble, siliceous and carbonaceous marble. Its thickness generally varies from 614 to 744 m and one of the thickest is about 1907 m in Kestanbulak.


Lithology Pattern: 
Reef limestone


Relationships and Distribution

Lower contact

The Beisainartag Formation conformably overlies the Sainartag Fm

Upper contact

It is unconformably overlain by the Nanhuan Beiyixi Fm tillite

Regional extent

Kuruktag region. The Beisainartag Formation was reported to be exposed in Xishankou of West Kuruktag (east of Korla City), eastward to Moqinkuduk, south valley of Xidashan in Middle Kuruktag) and Kestanbulak northwest of Xingditag, then to the south and west slope of Pargangtag south of Shanshan County (in East Kuruktag).


GeoJSON

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Fossils

The stromatolite-reefs are gradually increasing and commonly upwards preserved as lenticular or tubercle shapes, which include Inzeria multiplex, Patomia f., Gymnosolen Pargangensis, G. crass, Katauis minuta, Kotuikania f., Baicalia f., Jurusania conjunctiua, f. Procera, Tunggussia bassa, T. erecta, X. daskiosa etc. In addition there is oncolite Osagia f. etc.


Age 

middle QIngbaikouan (middle Tonian). The age of the Beisainartag Fm was determined to be 891.4 Ma and 850.4 Ma (Rb-Sr method). In addition, the volcanic rock in the bottom of the overlying Beiyixi Fm was determined to be 790.5 Ma. Therefore, the age of the Beisainartag Formation is older than 800 Ma, and probably referred to the Qingbaikouan System.

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.35

    Beginning date (Ma): 
902.00

    Ending stage: 
Tonian

    Fraction up in the ending stage: 
0.6

    Ending date (Ma):  
832.00

Depositional setting

The Beisainartag Fm is dominated by littoral subtidal to intertidal carbonate deposit, bearing abundant stromatolites and oncolites. With different size and shape, the stromatolite-reefs are distributed in the carbonate rock (shown as stratiform or hummocky shaped).


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.