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Changyanzi Formation

Changyanzi Fm


Period: 
Silurian

Age Interval: 
Telychian of Silurian (S1), (44)


Province: 
Sichuan

Type Locality and Naming

It was named and published by Jin Chuntai et al in 1989. The type section is located at the roadside from Longdanxi to Maliuqiao, east of Erlangshan Mts. in western Sichuan Province.

Synonym: (长岩子组)


Lithology and Thickness

The formation, 438 m thick, is dominated by grey and grey green thick-bedded mudstone and silty mudstone, locally with minor limestone lenses, calcareous nodules or medium-to-thin-bedded crystallized limestone.


Lithology Pattern: 
Shallow-marine marl


Relationships and Distribution

Lower contact

It conformably rests onto the underlying Longdanyan Fm

Upper contact

It conformably rests below the overlying Baohuoyan Fm

Regional extent

The formation is distributed in the Erlangshan Mts. area in west Sichuan Province.


GeoJSON

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Fossils

The fossils yielded include brachiopods, trilobites, conodonts, gastropods and bivalves. The fossil assemblages of brachiopod, trilobite and conodont are similar to those of the Longdanyan Fm.


Age 

Jin Chuntai et al (1989) assigned the formation to the age of Middle Wenlock epoch; however, we inclined to the idea of Rong Jiayu (1998, in Lin et al., 1998) that the age of Changyanzi Fm is probably equivalent to early Llandovery epoch according to the fossil groups and the stratigraphic sequence.

Age Span: 

    Beginning stage: 
Telychian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
435.76

    Ending stage: 
Telychian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
434.06

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wang Chuanshang and Wang Xiaofeng