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Langma Formation
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Langma Fm base reconstruction

Langma Fm

Period: 
Devonian

Age Interval: 
D1-2, (23) Early to Middle Devonian


Province: 
Xizang (Tibet)

Type Locality and Naming

The type section is located at Chaguoluoma, north of the Xainza County seat, Xizang (Tibet). It was named by Lin Baoyu in 1981.


Lithology and Thickness

Limestone. It is a set of carbonate rock deposits; 226 m in thickness. Lower part consists mainly of grayish-white to light-gray thick-bedded crystalline limestone, occasionally intercalated with oolitic limestone. Upper part is mainly composed of gray to grayish-white medium-bedded banded limestone.


Lithology Pattern: 
Limestone


Relationships and Distribution

Lower contact

The formation has a conformable basal contact to the underlying metamorphic quartzose sandstone (or it may be coarse-grained dolomite after Yao Jingguo et al, 1988) of the Deriangma Fm (Deri'angma Fm)

Upper contact

The formation is overlain by the grayish-white thick-bedded limestone of the Chaguoluoma Fm.

Regional extent

It is mainly distributed in Xainza and Ombu in Northern Xizang.


GeoJSON

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Fossils

It yields conodonts Polygnathus dehiscens, etc. in its base.


Age 

Early to Middle Devonian

Age Span: 
S

    Beginning stage: 
Emsian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
397.54

    Ending stage: 
Eifelian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
385.30

Depositional setting

It is interpreted as a carbonate platform facies.


Depositional pattern:  


Additional Information


Compiler:  

(Xian Siyuan)