Song Ca Fm

Period:

Ordovician, Silurian

Age Interval:

O_3-S sc, (16, 17)

Province:
North Trung Bo

Type Locality and Naming

The Song Ca Fm was described without stratotype (Dovjikov A.E. et al. 1965). Other authors have described it, but its stratotype had not been designated. Among the Suoi Dam, Huoi Kho, Huoi Hang and Huoi Thu sections described by Nguyen Van Hoanh (in Nguyen Van Hoanh et al 1978) the Huoi Thu section (N= 19°23’, E= 104°16’) can be selected as lectostratotype of the Song Ca Fm.

In the work of Vu Khuc, Bui Phu My et al. (1990) the Song Ca Fm, dated as O-S, corresponds to the lower part of the Song Ca Fm and lower part of the unit Undifferentiated Middle Paleozoic described in (Dovjikov A.E. et al. 1965), to the Suoi Mai Fm of Le Duy Bach (1969) and the lower part of Song Ca Fm of Tran Van Tri et al. (1977).

Synonym: Série du haut Song Ca: Fromaget J. 1928 (S-D). Hệ tầng Sông Cà: Mareichev A.M., Trần Đức Lương in Dovjikov A. E. và nnk.. 1965 (PZ 5 c); Trần Văn Trị và nnk. 1977 (S-D); Nguyễn Văn Hoành và nnk. 1978 (O₃-S₁); Phạm Kim Ngân, Lương Hồng Hược, Phạm Đình Long 1986 (O₃-S₁); Vũ Khúc, Bùi Phú Mỹ và «»£.1990) (O-S sc)\ Phạm Kim Ngân và nnk. 1994 (O₃-S); Tống Duy Thanh, Vù Khúc và nnk. 1995 (O₃-S), Trần Toàn và nnk. 1998 (O 3-S₁). Phức hệ Sông Cả: Tống Duy Thanh, Nguyễn Đức Khoa in Vũ Khúc và nnk. 2000 (O₃-S)

Lithology and Thickness

Huoi Thu stratotype, 2320 m thick, is: (1) Quartz-mica schist, quartzite sandstone, interbedded with siltstone, 470 m. (2) Polymictic sandstone, quartz-sericite schist, and in the uppermost part, clayey limestone; 850 m. (3) Gritstone, shale, sandstone and siltstone, 1000 m thick, containing Early Silurian graptolites.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Its lower boundary has not been observed.

Upper contact

The Song Ca Fm rests conformably under the Tay Trang Fm (= "Huoi Nhi Fm")

Regional extent

The Song Ca Fm occurs in two main bands; the first extends from Muong Xen, Tuong Duong to Quy Chau, Nghe An Province, the south Song Ca River band - from the Vietnamese-Laotian border west through Nghe An to Ky Anh, Ha Tinh Province.

GeoJSON

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Fossils

Some Silurian spores occur also in the formation, such as Zonosphaeridium sp., Leiotrichoid.es sp.

[Figure: Sông Cả Fm (O₃-S₂ sc): Silurian: Graptolites Monoclimacis vomerina, Pristiograptus kweichihensis (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

The Early Silurian graptolites occur in the upper part of the formation, therefore its lower part can be referred to the Upper Ordovician. The overlying Tay Trang Fm (=“Huoi Nhi Fm”) contains Early Devonian tentaculites, therefore the uppermost members of the Song Ca Fm can be referred to the Upper Silurian. So, the formation can be referred to the Upper Ordovician – Silurian (Wenlock)

Age Span:

Beginning stage:

Sandbian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

458.18

Ending stage:

Ludfordian

Fraction up in the ending stage:

1.0

Ending date (Ma):

422.73

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).