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Wotoushan Formation
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Wotoushan Fm base reconstruction

Wotoushan Fm

Period: 
Cretaceous

Age Interval: 
Early Cretaceous, K1wt, (32b)


Province: 
Sichuan

Type Locality and Naming

Sichuan Basin - south. The Wotoushan Formation was erected by the Sichuan Areal Survey Team in 1980. The section for the designation is along the highway from Sanhechang to Liujiachang of the Yibin County of Sichuan.

Synonym (or coeval): coeval with Gudian Fm (Sichuan Basin – central)


Lithology and Thickness

The Wotoushan Formation is mainly represented by brick-red thick-bedded sandstone with siltstone, mudstone and shale. It is persistent in lithology and is generally 200-500 m in thickness.


Lithology Pattern: 
Fine-grained sandstone


Relationships and Distribution

Lower contact

Its base is a disconformable contact marked by brick-red greatly massive gravel-bearing sandstone is distinguished from brown red mudstone of the Upper Jurassic Penglaizhen Fm. However, on regional stratigraphic columns, the next older, but largely coeval, unit is the Gudian Fm.

Upper contact

Its top in conformable contact with the Sanhe Fm that is dominated by brick-red moderately thick-bedded clayey sandstone with purple red clayey shale.

Regional extent

It mainly occurs in EW direction along the line linking Leshan, Yibin and Qijiang. It tends to increase in thickness from west to east.


GeoJSON

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Fossils

The formation yields ostracods Cypridea sichuanensis, C. angusticatudata, Monosulcocypris dorsipinula, M. sichuanensis; Charophytes Mesochara rymmetrica, M. stipitata; and bivalves Plicatounio naktongensis. Fossils are belong to ostracods Cypridea-(Morinina)-C.(Bisulcocypridea)-Monosulcocypris-Candona-Eucypris assemblage, and estheria Orthestheris-Halysestheria-Nemestheria assemblage.


Age 

The next older, but largely coeval, unit of the Gudian Fm (which is in central Sichuan Basin) is shown in Xi et al. (2019) as spanning late Aptian through Albian; but for graphic purposes to insert the Wotoushan Fm (lowest unit in south Sichuan Basin), the span is split in two.

Age Span: 

    Beginning stage: 
Albian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
106.85

    Ending stage: 
Albian

    Fraction up in the ending stage: 
0.75

    Ending date (Ma):  
103.68

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao