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Yudong Formation
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Yudong Fm base reconstruction

Yudong Fm

Period: 
Carboniferous

Age Interval: 
C11 (35a), late Tournaisian (early Early Carboniferous)


Province: 
Yunnan

Type Locality and Naming

The type section is lies around the Yudong Reservoir of Shidian County, Yunnan. It was named by Duan Lilan in 1973.

Synonym: Xiangshan Fm (lower)


Lithology and Thickness

Limestone. Gray-yellow and gray-black thin-bedded clayey limestone, micritic pellet limestone and crinoid stem-bearing limestone, containing glauconite. The bottom is a layer of brecciated calcirudite. Thickness 33 m, slightly varying laterally, thinning northward to Shangguan and Yunrui areas of Baoshan, and thickening eastward around Yangyi.


Lithology Pattern: 
Clayey limestone


Relationships and Distribution

Lower contact

Disconformable contact with the underlying Devonian Dazhaimen Fm

Upper contact

Conformable contact with the overlying Shihuadong Fm

Regional extent


GeoJSON

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Fossils

Rich in Conodonts Gnathodus pseudosemiglaber, Polygnathus sp., Protognathodus cordiformis, Bispathodus spinolicostatus and B. stabilis; small solitary Corals Zaphrentites, Pentaphyllum, Commutia, Sochkineophyllum, Rotiphyllum, etc.; Brachiopods Rhipidomella, Crurithyris and Eochoristites, as well as trilobites and plant fragments.


Age 

late Tournaisian (early Early Carboniferous). But Wang et al. (2019, China Integrated Strat) shows span as lower 3/4ths of Tournaisian.

Age Span: 

    Beginning stage: 
Tournaisian

    Fraction up in beginning stage: 
0.75

    Beginning date (Ma): 
349.87

    Ending stage: 
Tournaisian

    Fraction up in the ending stage: 
0.0

    Ending date (Ma):  
359.30

Depositional setting

It is interpreted as littoral-neritic deposits


Depositional pattern:  


Additional Information


Compiler:  

Wang Xiangdong