Cau Fm

Period:

Paleogene

Age Interval:

Oligocene, (31)

Province:
Vietnam Offshore south

Type Locality and Naming

Nam Con Son Basin. The type section is located within Hole Dua-IX (Lot 12) from a depth of 3680 to 4038 m (N = 7°36’; E = 109°5’) . It was named as the Cau (areca palm) Fm according to the tradition of naming offshore units.

Synonym: Hệ tầng Cau: Lê Văn Cự 1982, 1985. Điệp Cau: Đỗ Bạt 1986, 1993,2000. Hệ tầng Trà Tán: Ngô Thường San 1981; Võ Dương 1982.

Lithology and Thickness

Mainly grey sandstone interbeddcd with brown claystonc and siltstone. The quartz sandstone is fine- to coarse-grained with poor sorting, carbonate-clayey cement. The total thickncss of the formation in this hole reaches 358 m.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Unconformably upon rocks of the basement.

Upper contact

Unconformably under the Dua Fm

Regional extent

Nam Con Son Basin.

GeoJSON

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Fossils

Florschuetzia trilobata Zone. Characteristic palynomorphs are Florschuetzia trilobata accompanied by Magnastriatites. howardi, Pinuspollenites, Verrucatosporites, Osmunda, Gemmamonoles, Retitricolpites, Cyclophorus, Crudia and forms of the deltaic plain: Barringtonia, Calophyllum, Calamus and freshwater algae Pediastrum, Bosedinia mixed with foraminiferal shells. The Oligocene Florschuetzia trilobata Zone is determined by the presence of FI. trilobata and the absence of other species of Florschuetzia. The Oligocene age has been determined also by Verrutricolpites pachydermus and Mayeripollis

Age

Oiigocene.

Age Span:

Beginning stage:

Rupelian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

33.90

Ending stage:

Chattian

Fraction up in the ending stage:

1.0

Ending date (Ma):

23.04

Depositional setting

It was formed in the conditions of fast environmental change in different regions: continental facies in the N-NW and W-SW margins of the basin, deltaic facies and lacustrine-lagoonal in the E part.

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).