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Dasi Formation
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Dasi Fm base reconstruction

Dasi Fm

Period: 
Cretaceous

Age Interval: 
Early Cretaceous, K1dsi, (33b)


Province: 
Hubei

Type Locality and Naming

SE Hubei. The Dasi Formation was named by the No.4 Geological Brigade of the Hubei Bureau of Geology and Mineral Resource in 1977. The section for the designation is at Dasi 7 km southwest of the Baoan Township of Daye, Hubei. The Dasi Formation represents the set of eruptive rocks over the Lingxiang Fm and under the Donghu Fm around Dasi of Daye, Hubei, which was assigned to Early Cretaceous.


Lithology and Thickness

The Dasi Formation comprises a set of eruptive rocks, consisting of two cycles. First cycle is represented by purple red and purple gray felsite, rhyolite, kalitrachyte, andesite, breccia, agglomerate, siltstone and sandstone. Second cycle is brown gray and purple red plagioclase rhyolite, dacite, andesite, basalt, kalitrachyte, ignimbrite, tuff breccia, agglomerate and siltstone. It is 5161.62 m thick.


Lithology Pattern: 
Lava


Relationships and Distribution

Lower contact

The base of the formation, with appearance of breccia tuff, is different from the Lingxiang Fm comprising yellow green shale and light yellow siltstone interbedded with fine sandstone. It is in unconformable contact with the underlying strata.

Upper contact

The top is bounded unconformably by purple red silty mudstone at the base of the Donghu Gr.

Regional extent

The formation mainly occurs in Dasi and Damingshan -the Jinniu Town of Daye, eastern Hubei.


GeoJSON

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Fossils

None listed


Age 

The rhyolite whole rock K/Ar dating is of 96-132 Ma, with an average age of 121 Ma.

Age Span: 

    Beginning stage: 
Hauterivian

    Fraction up in beginning stage: 
0.4

    Beginning date (Ma): 
130.16

    Ending stage: 
Barremian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
121.40

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao