Tan Lam Fm

Period:

Devonian

Age Interval:

D? cb, (20)

Province:
North Trung Bo

Type Locality and Naming

Quang Tri and Thua Thien Hue provinces. Holostratotype - the section lying along the Co Bi River (Song Bo River), situated from the Phong Son pumping station, Phong Son Commune, Phong Dien District, Thua Thien - Hue Province, 5 km toward its upper course (E = 16° 29’; E = 107° 26'). The alternate name of the formation had been named in accordance with the former name of the river section at Co Bi Village.

Synonym: According to Tong-Dzuy Thanh and Vu Khuc (2011), even though Co Bai Fm or Cu Bai Fm is often used; the term Tan Lam Fm has the rule of priority. Les Fms de la rivière de Co Bi: Hoffct J.H. 1933 - Triassiques ?\ Bourret R. 1925. Dévonien non déterminé: Saurín E. 1956. 210. Hệ lầng Tăn Lâm (part.): Đặng Trần í 1uyên, Nguyễn Đình Hồng 1980; Nguyễn Đức Khoa et al. 1981; Nguyễn Đức Khoa 1984; Tống Duy Thatih et al. 1986 1988 (Dj); Nguyễn Văn Hoành, Phạm Huy Thông 1984; Nguyền Văn Trang et al. 1985; Vũ khúc, Bùi Phú Mỳ 1989 (D,.2). Tân Lảm Fm: Tống Duy Thanh 1993 (D₁). Hệ 1ầng Cô Bi: Nguyễn Hữu Mùng 1995 (D ?)

Lithology and Thickness

Sandstone: Typical section is about 100m: (1). Conglomerate, sandstone, siltstone, 60 m. (2). Brown sandstone with brown-grey to dark-grey shale, 40 m.

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

The formation rests conformably on the Silurian Dai Giang Fm

Upper contact

Upper boundary not observed. Next younger regional unit is the Upper Devonian - Lower Carboniferous limestone of Cu Bai Fm.

Regional extent

Apart from the two sections above the Tan Lam (Co Bi) Fm occurs in many other localities in Thua Thicn - Hue Province. In the A Tep section situated near the Viet Nam - Laos border the formation begins with a 120 m thick member of basal conglomerate and gritstone covering granite of the Dai Loc Complex Fm.

GeoJSON

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Fossils

Red-brown shale interbeds in lower portion has inarticulate brachiopods of Lingula aff. loulansis, L. cf. cornea, L. aff. hawkei, etc.

[Figure: Tân Lâm Fm: Brachiopods Lingula aff. loulanensis (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

Early Devonian on basis of fossils.

Age Span:

Beginning stage:

Lochkovian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

419.00

Ending stage:

Emsian

Fraction up in the ending stage:

1.0

Ending date (Ma):

394.30

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).