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Dongwu Formation
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Dongwu Fm base reconstruction

Dongwu Fm

Period: 
Neoproterozoic

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


Province: 
Xinjiang

Type Locality and Naming

Aksu-Kalpin region. The Dongwu Fm was named by Gao Zhenjia et al. in 1986 and formally published by Lu Songnian et al. in 1992. The typical section is located in Dongwu, 4 km southeast of Yourmeinak village, and the reference section is in Qiaoenbulak, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region). Highest formation of Qiaoenbulak Gr.

Synonym: （东屋组）


Lithology and Thickness

The Dongwu Fm is composed of thick-bedded, massive pebbly grit, sandy conglomerate intercalated with minor grayish green fine sandstone and siltstone. The thickness of the Dongwu Formation is 175 m.


Lithology Pattern: 
Aus conglomerate


Relationships and Distribution

Lower contact

With an obvious sedimentation hiatus, the basal part rests disconformably or locally unconformably onto the underlying Muyangtan Fm

Upper contact

The Dongwu Fm is unconformably overlain by the Yourmeinak tillite where there are well-preserved glacial pavements, or it is immediately overlapped by the Upper Sinian Sugetbulak Formation if the tillite is absent.

Regional extent

Aksu-Kalpin region.


GeoJSON

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Fossils

Besides few microplants, only the trace fossil (Planolites sp.) was reported.


Age 

Strat column schematically shows as upper-quarter of Qingbaikous (late Tonian

Age Span: 

    Beginning stage: 
Tonian

    Fraction up in beginning stage: 
0.4

    Beginning date (Ma): 
888.00

    Ending stage: 
Tonian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
860.00

Depositional setting

It has graded beddings (fine gravel to coarse to medium to fine sand-silt), which represents the character of the E graded part of Bouma turbidite beds. Each graded bed has a recorded thickness of 60 to 120 cm, and its surface has underwater wash on which some undulatories are similar to watercourse. It is thus considered to have been deposited in or near the deep-water supply channel of an underwater fan (Lu Songnian et al. 1990).


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.