Dam Doi Fm

Period:

Neogene

Age Interval:

middle Miocene (N₁², dd) (30)

Province:
Vietnam Offshore south

Type Locality and Naming

Malay Basin. The type section is located borehole Dam Doi drilled in lot 46 by the Fina Co, at a depth of 1000 to 1465 m (N = 7°12', E = 104°0’). It was named by Đỗ Bạt 2002.

Synonym: Hệ tầng Đầm Dơi: Đỗ Bạt 2002.

Lithology and Thickness

Light grey, fine- to medium-grained calcareous sandstone, containing thin interbeds of white-grey limestone or marl, claystone and some brown coal seams. The thickness of the formation in this borehole is 465 m. Apart from above terrigenous beds, sometimes there still are grey to yellow-brown dolomite or microgranular limestone beds. Claystone members are possibly good confining beds for petroleum reservoirs of the underlying Ngoc Hien Fm. Sandstone mainly has good porosity and permeability.

Lithology Pattern:

Fine-grained sandstone

Relationships and Distribution

Lower contact

Conformably upon the Ngoc Hien Fm.

Upper contact

Unconformably overlain by the Minh Hai Fm.

Regional extent

The Đầm Dơi Fm is largely distributed in the Malaya - Tho Chu Basin with the thickness of 300-1200 m.

GeoJSON

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Fossils

The collected spores and pollens belong to the Florschuetzia meridionalis - FI. levipoli Assemblage with the presence of FI. meridionalis, Eugeisonia irtsignis, Comptostemon that have the FAD in Middle Miocene. Among forams, there are Middle Miocene forms of the N9- N13 Zones, such as Orbulina universa, Globorotalia mayerii, Gl. fohsi, Gl. continuosa. Nannoplanktons characterize the NN6-NN9 Zones with Discoaster deflandres, Disc. hamatus, Disc. kugleri of Middle Miocene age.

Age

Middle Miocene on the paleontological assemblages.

Age Span:

Beginning stage:

Langhian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

15.99

Ending stage:

Serravallian

Fraction up in the ending stage:

1.0

Ending date (Ma):

11.63

Depositional setting

It is interpreted as coastal wet delta sediments interbedded with many members of littoral and shallow-sea sediments.

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).