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Mesoproterozoic

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Bowamu Gr

Bowamu Gr

Period: 
Mesoproterozoic

Age Interval: 
Changchengian (Statherian) Ch (7)


Province: 
Xinjiang

Type Locality and Naming

NE Tarim Basin. The Bowamu Gr was named by Gao Zhenjia et al. in 1993. The type section is at Bowamubulak, southwest of central Kuruktag, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region).

Synonym: （波瓦姆群）


Lithology and Thickness

The group is subdivided into two subgroups. Lower subgroup, 550 m thick, is composed of quartzite, marble and mica schist. The base consists of meta-conglomerate in which the pebbles were elongated owing to the deformation process. Upper subgroup is of interbedded quartzite, spotted epidote, biotite schist and two-mica schist, occasionally with marble. It is about 2000 m thick.


Lithology Pattern: 
Sandstone


Relationships and Distribution

Lower contact

The Group is in unconformable contact with the underlying Xingditag Gr.

Upper contact

The top of the upper subgroup unconformably overlain by the Airjigan Gr.

Regional extent

NE Tarim Basin. Along the strike the upper stratigraphic horizon of this group is equivalent to the Yangjibulak Gr.


GeoJSON

null

Fossils


Age 

The two-mica schist in the lower part of lower subgroup was dated at 728.23 ±279.73 Ma by Rb-Sr isochron on whole rock. The muscovite was dated by K-Ar at 749.5 Ma (Gao Zhenjia, 1993). Based on these isotopic datings and other relevant data of the lower and upper subgroups, the geologists attributed the group to the Changchengian (= Statherian). [Note by J.Ogg – perhaps the dates in this entry should be 1749.5 Ma (not "749.5"), which would be in Changchengian?] For graphic purposes, placed below the partly coeval Yangjibulak Gr.]

Age Span: 

    Beginning stage: 
Statherian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
1,800.00

    Ending stage: 
Statherian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
1,600.00

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Extracts from The Mesoproterozoic Erathem (chapter in Stratigraphic Lexicon of China, draft of 2022) by Gao Linzhi, Ding Xiaozhong, Zhang Chuanheng, Zhang Heng.