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Xichahe Formation

Xichahe Fm


Period: 
Devonian

Age Interval: 
D1-2 (45, 46), Early to Middle Devonian


Province: 
Shaanxi, Gansu

Type Locality and Naming

The type section is located at Dajiagou of Penjia Village, Xundian County of Shaanxi Province. It was named by Shaanxi Geological Survey in 1980, and was published in 1983 by Paleontological Atlas of Northwest China, Volume San-Gan-Ning.


Lithology and Thickness

Conglomerate, sandstone. Lower part of the Formation is composed of grayish-green and dark-gray siliceous conglomerate intercalated with pebbly feldspar quartz sandstone. Upper part consists of grayish-green and dark-gray thin-bedded feldspar quartz sandstone and sandy slate with lenses of conglomerate and coarse-pebbly sandstone. The Uppermost part has slate with dolomitic limestone. The usual thickness of the Formation is 190 m, but the maximum thickness reaches 590-670 m in the Gongguan-Huilong area.


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

Unconformity onto Silurian.

Upper contact

The formation is conformably overlain by the Gongguan Fm dolomite.

Regional extent

Gongguan-Huilong area, Gongguan-Xichahe area.


GeoJSON

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Fossils

The uppermost Formation yields bivalve Grammysia sp., Cypricardinia sp., Edmondia sp., and Glassites cf. concentricus.


Age 

The Formation is diachronous in age from Lower Devonian in the Gongguan-Xichahe area to Middle Devonian in the Shangjin-Songsuping area.

Age Span: 

    Beginning stage: 
Pragian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
412.40

    Ending stage: 
Emsian

    Fraction up in the ending stage: 
0.1

    Ending date (Ma):  
408.89

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

(Cao Xuanduo)