Dong Nai Fm

Period:

Neogene

Age Interval:

Late Miocene; N₁³, (27)

Province:
Vietnam Offshore south

Type Locality and Naming

Cuu Long Basin. The type section is established in borehole GK.15G-1X drilled in the Dong Nai Structure (E = 10°25 ; E = 108°21 ).

Synonym: Hệ tầng Đồng Nai: Ngô Thường San 1981, 1988; Đỗ Bạt 1993,2000. Hệ tầng Vàm Cò:Lê Văn Cự 1982. Điệp Côn Sơn: Đỗ Bạt 1986.

Lithology and Thickness

In the stratotype borehole, from 1330 to 650 m depth, the formation comprises fine- to medium- grained sandstone, sandy gritstone grading upwards into sandstone interbedded with siltstone, claystone and coal. Locally sandstone contains pyrite and glauconite. The logging curve clearly differentiates, showing that the coarse-grained component plays the main role. The thickness of the formation at this borehole is 680 m.

Lithology Pattern:

Coarse-grained sandstone

Relationships and Distribution

Lower contact

Unconformably upon the Con Son Fm

Upper contact

Unconformably below the Bien Dong Fm

Regional extent

Cuu Long Basin.

GeoJSON

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Fossils

Amautholithus delicatus, Calcidiscus leptoporus, Calc, marcintyrei, Coccolithus miopelagicus, Cocc. pliopelagicus, Discoaster browweri, Disc, variabilis, Helicosphaera careiry, H. kamptneri, Pontosphaera japónica and Reticulofenestra pseudoumbilical.

Age

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:

1.0

Ending date (Ma):

5.34

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, 2^nd edition; 2011; English edited by A. Boucot).