Minh Hai Fm

Period:

Neogene

Age Interval:

late Miocene (N₁³, mh) (30)

Province:
Vietnam Offshore south

Type Locality and Naming

Malay Basin. The type section is located in Minh Hai Borehole (GK.51-MH-1X) at a depth of 690 to 1097 m (N = 7°28’; E = 103°40’). It was named by Đỗ Bạt 2002

Synonym: Hệ tầng Mirth Hải: Đỗ Bạt 2002.

Lithology and Thickness

The stratotype consists of greenish-grey to light-grey claystone interbedded with light-grey, fine to coarse sandstone and some brown coal seams. The thickness of the formation in this borehole is 407 m. In other areas, the Fm is composed of much light-grey to brown-grey clay and claystone interbedded with minor light-grey silt-siltstone, sand-sandstone, sometimes, dolomite and microgranular limestone. Coaly shale and coal seams occur usually in the lower part of the section. The thickness of the Fm varies from 300 to 500 m.

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Unconformably upon the Dam Doi Fm

Upper contact

Unconformably under the Bien Dong Fm

Regional extent

Malay Basin

GeoJSON

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Fossils

Spores and pollen: Florschuetzia meridionalis – Stenochlaena laurifolia - Anthocerisporites Assemblage; FI. levipoli, FI. trilobata. As for forams, beside benthic species of the Pseudorotalia, Asterorotalia group, there still is the planktonic Globigerinoides immaturus, Gds. ruber, Gds. acostaensis, Sphaeroidinellopsis semỉỉuna Complex with the characteristic form Gds. acostaensis belonging possibly to the N16-N18 Zones of Upper Miocene. Nannoplanktons comprise characteristic Late Miocene forms of the NN10-NN11 Zones, such as Discoaster quinqueramus and Disc. bergreni.

Age

Late Miocene age has been determined on the paleontological basis.

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

Coastal marshy and shallow-sea sediments with strong terrigenous influence.

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).