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Bao Loc Formation

Bao Loc Fm

Period: 
Neogene

Age Interval: 
Late Miocene (bl), (24)


Province: 
South Trung Bo

Type Locality and Naming

Central Lam Dong Province (Lam Dong Basin). Named after Bao Loc area (N = 11.6°; E = 108.1°). Described by Trinh Dahn (in Vu Khuc et al., 1984).


Lithology and Thickness

Lacustrine, coal-bearing beds. The characteristic section has a thickness of 150-200 m, which includes pebble-bearing sandstone, grey siltstone and claystone containing much organic matter, interbedded with tholeiitic basalt and volcanic breccias. Grading upwards into sandstone interbedded with black-grey claystone.


Lithology Pattern: 
Clayey sandstone


Relationships and Distribution

Lower contact

Unconformably rests on older sediments. Next older regional units are the Late Cretaceous volcanics of the Don Duong Fm and the Nha Trang Fm.

Upper contact

Unconformably overlain by the Di Linh Fm of Pliocene.

Regional extent

Occurs in small areas in the Bao Loc, north Di. Linh, Duc Trong and Da Lat.


GeoJSON

null

Fossils

Upper part of section yields remains of the Na Durong Flora and the gasưopod Viviparus aff. quadratus.


Age 

K/Ar isotopic age on the basalt yields 9-16 Ma. Based on the presence of brown coal, the Fm has been correlated to the Song Ba Fm in the Tay Nguyen basins and dated as Late Miocene.

Age Span: 

    Beginning stage: 
Tortonian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
11.63

    Ending stage: 
Messinian

    Fraction up in the ending stage: 
1.o

    Ending date (Ma):  
7.23

Depositional setting

Lacustrine and coal-bearing terrestrial deposits


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).