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Suoi Bang Formation
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Suoi Bang Fm base reconstruction

Suoi Bang Fm

Period: 
Triassic

Age Interval: 
Middle Norian-Rhaetian (T3n-r sb) (9, 11, 14 15)


Province: 
Viet-Laos NW, West Bac Bo

Type Locality and Naming

Coal-bearing formation in Song Da-Tu Le and Muong Te basins. Described by Dovzhikov et al., 1965; with characteristic section in the Suoi Bang area.

Synonym: Suoi Bang Gr, with upper Suoi Loi Fm and lower Muong Va Fm (as used by Tong-Dzuy Thanh and Vu Khuc (Editors; Stratigraphic Units of Viet Nam, 2011; but merged as a single Suoi Bang Fm by Tran Van Tri and Vu Khuc (Editors; Geology and Earth Resources of Viet Nam, 2011) [Used here.]


Lithology and Thickness

Lower part (also called Muong Va Fm) consists of terrigenous beds with interbeds of carbonate containing Norian marine mollusks; and Upper part (also called Suoi Loi Fm) is coal-bearing continental beds with interbeds containing marine-brackish water fauna. Characteristic section (1000 m thick) has 3 parts: (1). Dark-grey siltstsone and shale, 212 m, with mollusk fossils. (2) Mainly light-grey sandstone, 425 m, with similar fossils to the lower unit. (3) Grey to dark-grey siltstone with plant debris, grading upward into grey sandstone; contains some lean-coal beds; 270 m. Coal has been exploited, but serves only local industry.


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

Unconformably overlies the Carnian-age Nam Mu Fm (in western West Bac Bo), or the Ladinian-age Lai Chau Fm (Viet-Laos NW)

Upper contact

Grades upward into the continental red beds of the Nam Po Fm

Regional extent

Distributed in large bands or areas in the Ninh Binh, Lai Chau, Dien Bien, and Son La provinces.


GeoJSON

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Fossils

Lower pair of units has Norian mollusks and bivalves, and lowermost has Middle Norian ammonoid of Juvavites magnus (middle zone of Middle Norian). Upper unit has marine and brackish-water bivalves of Rhaetian.


Age 

Dated by mollusks-bivalves as middle ammonoid zone of Middle Norian through Rhaetian.

Age Span: 

    Beginning stage: 
Norian

    Fraction up in beginning stage: 
0.3

    Beginning date (Ma): 
220.83

    Ending stage: 
Rhaetian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
201.36

Depositional setting


Depositional pattern:  

Additional Information


Compiler:  

Tran Van Tri and Vu Khuc (Editors; Geology and Earth Resources of Viet Nam, General Dept. of Geology and Minerals of Viet Nam; completed in Dec., 2011), with additional details from Tong-Dzuy Thanh and Vu Khuc (Editors; Stratigraphic Units of Viet Nam, 2nd edition; 2011; English edited by A. Boucot).