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Qigaisu Gr
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Qigaisu Gr base reconstruction

Qigaisu Gr

Period: 
Devonian

Age Interval: 
D2-D31 (17),


Province: 
Qinghai

Type Locality and Naming

The type section is located at west of Qigaisu River of northern slope of Kunlun Mts., Gelmu County of Qinghai Province. It was named by No. 8 Team of Qinghai Petroleum Survey in 1958 and was published in Qinghai Compiling Group for Regional Stratigraphical Scale.


Lithology and Thickness

Volcanics, Sandstone and Claystone. Lower part (volcanics) is composed of grayish dark and purplish-red volcanic rocks of andesite, rhyolite and lamprophyre. Middle part is composed of grayish-green and purplish-red medium-fine-grained sandstone, siltstone and sandy slate intercalated with a few beds of conglomerate. Upper part is purplish-red slate. In the type area, the Group recorded an incomplete thickness of 2194 m.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

Its lower boundary is not exposed.

Upper contact

The upper boundary is a disconformable contact with the overlying Lower Carboniferous. In a nearby region (same generalized column 17) are the Late Devonian volcanics of the Harza Fm.

Regional extent

Eastward to Tuolahe River, it is 1982 m thick, and mainly consists of feldspar sandstone intercalated with volcanic breccia.

At Jucheshan, it consists of feldspar sandstone, pebbly sandstone, siltstone and basalt, is 881 m in thickness, and its upper part is dominated by volcanic lava intercalated with clastics that can be divided into several cycles, from basic to acidic, of volcanic eruptions and sedimentation.


GeoJSON

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Fossils

Fossils of chitinozoans and spore have been found in the middle part, and fragments of Asterolepiformis and ?Protolepidodendron in the upper part.


Age 

Generalized as lower and middle Devonian on regional column (no direct age control). For graphic purposes, put as Pragian through Givetian

Age Span: 

    Beginning stage: 
Pragian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
412.40

    Ending stage: 
Givetian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
378.90

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

(Wang Shitao)