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Na Dang Formation

Na Dang Fm

Period: 
Devonian

Age Interval: 
Givetian, (3)


Province: 
Viet Bac

Type Locality and Naming

Stratotype in the Lung Hoai – Sa Tao section extends from Huyen Giu to Na Dang (Cao Bang Province) = same section as the underlying Ban Cong Fm; named by Nguyen Cong Thuan (2005). Similar to the Na Quan Fm in the same general area, but has been considered an independent formation because between these two units there still is the massive limestone of the Ban Cong Fm.


Lithology and Thickness

Stratotype is 300 m of mainly thin- to medium-bedded limestone, clayey limestone, dark-grey cherty limestone and cherty shale; containing abundant Givetian-Frasnian stromatoporoids and brachiopods.


Lithology Pattern: 
Limestone


Relationships and Distribution

Lower contact

Conformable on the Ban Cong Fm

Upper contact

Conformable below the Bang Ca Fm

Regional extent

Within the Cao Bang Province


GeoJSON

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Fossils

Abundant fossils include rugose, heliolitoid and tabulate corals (e.g., Favosites, Squameofavosites), coniconchs and brachiopods.


Age 

The paleontological collection indicates a Givetian-Frasnian age. [But conformable above/below to formations that also include Givetian fossils.]

Age Span: 

    Beginning stage: 
Givetian

    Fraction up in beginning stage: 
0.4

    Beginning date (Ma): 
382.74

    Ending stage: 
Givetian

    Fraction up in the ending stage: 
0.8

    Ending date (Ma):  
380.18

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).