Van Canh Fm

Period:

Devonian

Age Interval:

Early Devonian, D₁vc, (6)

Province:
Vietnam Offshore North

Type Locality and Naming

Lower formation (seaward) of the Do Son Gr. Western side of Van Canh Island (N = 20°52'22", E = 107°20'14"), 3.5 km N-NW of Ngoe Vung Harbour. The Van Canh Fm is synchronous with the Duong Dong Fm in the more landward sections.

Synonym: Hệ tầng Vạn Cảnh: Nguyễn Hữu Hùng, Tạ Hòa Phương, Nguyễn Thị Thúy 2007 (D 1). Grès de Do-son (part.): Lantenois H. 1907; Saurin E. 1956 (D), 1958 (Dj). Eifelian Stage (part.): Jamoida A.I. (in Dovjikov A.E. ei al. 1965). Hê tầng Kiến Án (part.): Nguyền Quang Hạp 1967 (S₂). Điệp Sông Cầu (part.): Trần Văn Trị, Nguyễn Đình Uy 1975, 1977 (Dị). Điệp Đồ Sơn (part.): Nguyễn Công Lượng et al. 1980 (DO; Tống Duy Thanh et al. 1986; Vũ Khúc, Bùi Phú Mỹ et al. 1990 (Dj); Ngô Quang Toàn 1994 (D₃-C₁); Tống Duy Thanh (in Vũ Khúc ei al. 2000) (D). Do Son Fm (part.): Tong-Dzuy Thanh et al. 1988 (D₁); Long J. et al. 1990; Tong-Dzuy Thanh, Janvier Ph. et al. 1992 (D₂gv-D₃); Janvier Ph., Racheboeuf p., H. Nguyên Huu, T. Doàn Nhât 2003 (S₂?-Dj); Nguyễn Hữu Hùng et al. 2004 (D₁-D₂gv); Tong-Dzuy Thanh, Ta Hoa Phuong 2006 (Djgv-TDjfr ds). - La Fm de Sika à Dó Son: Janvier Ph., Blieck, Gerrienne et Tong-Dzuy Thanh 1987 (D₁). > The

Lithology and Thickness

Sandstone and calcareous siltstone. In Chau Dap Island, in the section extending to the southwestern cape of Tra Ban Island, white-grey, medium- to thick-bedded sandstone and calcareous siltstone are exposed, Thickness: >500 m; On Tra Ban Island, sediments of the Van Canh Fm are exposed along the talus of the road extending from the People’s Committee Headquarter of the Ban Sen Commune to the Dong Danh Hamlet, including greenish-grey micaceous sandstone, micaceous siltstone, greyish, red-brown weathering mica schist. Thickness: >500 m.

[Figure: Vạn Cảnh Fm: Terrigenous sediments Outcrop (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Lithology Pattern:

Siltstone

Relationships and Distribution

Lower contact

Conformable on the Kien An Fm (Silurian) has been observed in the An Lao araea, Hai Phong City.

Upper contact

Conformable under the Van Huong Fm (Givetian)

[Figure: Vạn Hương Fm: Lower boundary on Van Canh Fm (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Regional extent

On Ngoe Vung Island, the best section of the Fm is exposed along the road extending from Ngoe Vung Harbour to the ccntre of the Ngoe Vung Commune. These beds plunge southwestwards with a dip of 40-45°. In right talus on the road, about 200 m south of Ngoe Vung Harbour, brown-grey micaceous siltstone crops out, This section is continuously exposed along the road for an interval of 2 km, from the harbour to the ccntre of Ngoe Vung Island Commune. On Cong Tay Island,

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[106.91,21.3],[107.09,21.37],[107.27,21.37],[107.53,21.41],[107.78,21.29],[107.61,20.97],[107.4,20.76],[107.22,20.69],[107.03,20.79],[106.86,21.04],[106.91,21.3]]]]}}

Fossils

Includes Calamospora sp., Retusotriletes rotundas, R. warringtonii, Apiculiretusispora sp., Dictotriletes subgranifer, Emphanisporites neglectus, E. cf. micronatus, Archaeozonotriletes sp. together with the acritarch Veryhachium sp..

[Figure: Vạn Cảnh Fm: Plant fossils (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

Early Devonian to Eifelian

Age Span:

Beginning stage:

Lochkovian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

419.00

Ending stage:

Eifelian

Fraction up in the ending stage:

1.0

Ending date (Ma):

385.30

Depositional setting

The results of iithological, gcochemical and paleontological studies show that sediments of the Van Canh Fm were deposited in a nearshore gulf environment.

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).