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Wuzunsayi Formation

Wuzunsayi Fm

Period: 
Triassic

Age Interval: 
Early Triassic (TJ17)


Province: 
Xinjiang

Type Locality and Naming

Li Yong’an et al. named this formation in 1989. The named section is located on the east bank of the Duwa River in Pishan County (north limb of anticline), Xinjiang, and the reference section is located on the east bank of the Duwa River in Pishan County (south limb of anticline).

Synonym: mistakingly included in Ye’erqiang Group (See discussion in "Age" below)


Lithology and Thickness

Lithology can be divided into two members. The lower part of the Lower member is mainly yellow gray sandstone, the upper part is gray, purple gray silty mudstone and fine sandstone with a thickness of 68 m. Upper member is gray, green gray mudstone, fine sandstone and silty mud stone, top is purple brown, yellow gray thick gravel bearing sandstone, with the thickness of 209.7 m.


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

The lower part is in disconformable contact with the Upper Permian Duwa Fm (although regional column here for the Permian suggests the Upper Permian Aqia Gr is below)

Upper contact

The top part is cut off by a fault. Schematic stratigraphic column shows next younger regional unit is the Ye'erqiang Gr (= Yarkant Gr , Shalitashi Fm).

Regional extent

This formation is only found in about 6 km2 area of Cunwa area, Pishan County. However, geophysical and drilling data show that this formation still exists from the north to the middle of the basin.


GeoJSON

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Fossils

Mono-spores species: Limatulasporites-Lundbladispora-Cycadopites (Monosulcites) assemblage; Megaspores: Trileites(Calamospora)-Pusulosporites inflatus-Annuletes assemblage. Conchostracans in Duwa area: Punctestheria multilineatus, P. triangularis P. elliptica, Cornia cf. samarica


Age 

In 1966, a set of purple red, gray red, gray black sandstone and mudstone interbedded siltstone strata in the Duwa, Pishan area was classified into the lower part of the Jurassic Ye’erqiang Group by Liu Zizhao and Zhou Dexu. In 1985, 1∶200, 000 geological map of Xinjiang, the strata were classified as Cretaceous. In 1985, Qu Lifan and He Zhuosheng studied the palynology, concluded that it belongs to the late Early Triassic. In 1989, Li Yong ‘an concluded that it belongs to the late Early Triassic. In 1989, Li Yong‘an et al also considered it to be Triassic and named it Wuzunsayi Group. In 1992, according to the stratigraphic sequence and microspore fossils of 4 sections at the Duwa anticline and James Dewar Anticline, Li Peixian, Yang Jiduan et al. determined that the age was only late Early Triassic and changed from a group to a formation ranking.

Age Span: 

    Beginning stage: 
Olenekian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
249.88

    Ending stage: 
Olenekian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
246.70

Depositional setting

This formation belongs to lacustrine facies.


Depositional pattern:  


Additional Information


Compiler:  

Yang Jiduan, Yu Yingyue and Tong Jinnan