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Xichangjing Formation
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Xichangjing Fm base reconstruction

Xichangjing Fm

Period: 
Neoproterozoic

Age Interval: 
late Nanhuan (late Cryogenian), Nh (5, 6)


Province: 
Inner Mongolia, Gansu

Type Locality and Naming

Beishan. The Xichangjing Fm was named by Tang Guangzhong, Yu Yisheng and Zhao Wenjie in 1978-1979 and published in 1984. The naming section is located south of Xichangjing, Ejin Qi, Inner Mongolia.

Synonym: （洗肠井组） ; Xicangjin Fm (spelling)


Lithology and Thickness

The Xichangjing Fm consists of gray, blue gray, purple-red, gray green, yellowish brown tillite (diamictite), pelodite, laminated slate with interbeddings of pebbly calcareous mudstone, pebbly dolomite and graywacke. It obviously shows character of tillite, with massive conglomerate showing no stratification and sorting, with pebbles in different size and different forms with obvious nail-head striation, indentation and pressed fracturing. The thickness changes a lot, 105 -376 m thick.


Lithology Pattern: 
Glacial till


Relationships and Distribution

Lower contact

The bottom of the formation is unconformable with the underlying Tongchangkou Fm and it overlaps different horizons of the underlying strata.

Upper contact

The upper part of the formation is conformable with the overlying Hongshankou Fm (base of Ediacaran)

Regional extent

Beishan. Inner Mongolia and northernmost Gansu. The formation is widely distributed from Fangshankou on the west, through Zelumu, Shuangyingshan, eastwards to Xichangjing and Hongshankou, Ejin Qi, Inner Mongolia.


GeoJSON

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Fossils


Age 

late Nanhuan (late Cryogenian) glacial; for graphic purpose assumed coeval with Marinoan glacial.

Age Span: 

    Beginning stage: 
Cryogenian

    Fraction up in beginning stage: 
0.94

    Beginning date (Ma): 
640.10

    Ending stage: 
Cryogenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
635.00

Depositional setting

Diamictite


Depositional pattern:  


Additional Information

The isotopic dating (535.7 Ma Rb-Sr) was gained from cement of tillite and slate of glaciofluvial origin. So, the age may be also possible of Early Cambrian.


Compiler:  

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