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Liangquan Formation
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Liangquan Fm base reconstruction

Liangquan Fm

Period: 
Devonian

Age Interval: 
D12 (24), Pragian (middle Early Devonian)


Province: 
Xizang (Tibet)

Type Locality and Naming

The type section is located on the hill ridge, east of Liangquan of Nyalam County, Xizang; the reference section is nearby Kede of Pazhu Township in Tingri (Xêgar) County, Xizang (Tibet) Autonomous Region. It was named by Wang Yigang et al. in 1974.


Lithology and Thickness

Shale, limestone. It is composed of interbeds between grayish-white shale and gray thin-bedded limestone, and also of light-gray silty mudstone which may change into grayish-green or grayish-white in color after weathering.

It is 40 m in thickness.


Lithology Pattern: 
Pelagic marl


Relationships and Distribution

Lower contact

The Formation has a conformable contact to the light- to dark-gray limestone of the Pulu Fm of the Upper Silurian. [NOTE: Lexicon chart had indicated a fault contact at the reference section; and therefore base- Liangquam Fm is base-Pragian, and Lochkovian is unknown.]

Upper contact

The Formation is overlain by the light-gray feldspathic quartz sandstone of the Poqu Fm (see Boqu Gr).

Regional extent

It is mainly distributed in Burang, Zanda (Toling) and Zhongba counties, at Yali of Nyalam County, at Kede of Pazhu in Tingri County, and at Yadong County in southern Xizang. Eastward and westward from Nyalam, the thickness of the formation may reach approximately 400 m.


GeoJSON

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Fossils

The formation contains a large number of tentaculites of Nowakia acuaria Zone, graptolites of Monograptus Yukonensis Zone, belonging to Pragian in age.


Age 

Pragian (middle Early Devonian)

Age Span: 
S

    Beginning stage: 
Pragian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
412.40

    Ending stage: 
Emsian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
397.54

Depositional setting

It is interpreted as a deep-water basin facies deposits.


Depositional pattern:  


Additional Information


Compiler:  

(Xian Siyuan)