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Tam Lung Formation
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Tam Lung Fm base reconstruction

Tam Lung Fm

Period: 
Jurassic

Age Interval: 
Late Jurassic, (J3 tl), (4)


Province: 
East Bac Bo

Type Locality and Naming

An Chau and Song Hien basins. Named after Tam Lung Mt area; described by Vu Khuc and Dang Tran hyen, 1995.

Synonym:


Lithology and Thickness

Volcano-sedimentary beds. Tam Lung Mt section has 550-600 m of (1) Basal conglomerate, gritstone, sandstone, from grey to red-brown clay shale and siltstone; 50 m. (2) Rhyolite tuff, subalkaline, rich in pink kalifeldspath porphyritic rhyolite, rhyotrachyte interbedded with tuffaceous conglomerate and gritstone containing volcanic breccia grains, 500-550 m.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

Unconformable upon Lower-Middle Triassic sediments in type areas. Regionally, the next older unit is the Ha Coi Fm of Lower-Middle Jurassic.

Upper contact

Regionally, the next younger unit is the Cretaceous-age Ban Hang Fm.

Regional extent

Two areas: (1) Lang Son Province in a band from Khau Ma – Tam Lung Mt area extending to Quyt Slope (SE of Dong Dang Townlet); and in a second band fom the Keo Ga area extending to Na Tinh one (S. of Lang Son City). (2) Tam Dao Range, forming small exposures lying along faults on both sides.


GeoJSON

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Fossils


Age 

Late Jurassic age has been supposed on the basis of stratigraphic relations and correlation to acidic-alkaline volcanic flows formed in the continental environment in other areas of the country.

Age Span: 

    Beginning stage: 
Oxfordian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
161.53

    Ending stage: 
Tithonian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
143.10

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).