Bo Hieng Fm

Period:

Silurian

Age Interval:

Late Silurian, S_3-4bh, (11)

Province:
West Bac Bo

Type Locality and Naming

Its stratotype occupies the lower part of the Bo Tao - Phu Chuot section, from Bo Tao to Tien Ban villages (on the bank of the Song Da River), situated near Bo Hieng Village, Son La Province (N= 20° 53’; E= 104° 56'). Nguyen Vinh (1977).

Synonym: Điệp Bó Hiềng-. Nguyễn Vĩnh in Phan Cự Tiến et al. 1977 S₂ –D₁, in Vũ Khúc, Bùi Phú Mỹ el al. 1990 (S₂ - Dj); Dương Xuân Hảo et al 1980 (S₂-D₁); Tống Duy Thanh et al. 1986 (S); Trần Đức Lương, Nguyễn Xuân Bao 1994 (S1-D₂); Tạ Hòa Phương, Lê Văn Mạnh, 1996 (Hệ tầng - S₂); Tống Đuy Thanh in Vũ Khúc et al. 2000 (Hệ tầng). Etage de marnes de Ban-Hom: Deprat J. 1914 (Gothlandian); Dussault L. 1929 (D); Saurin E., 1956 (Di em- Dje).

Etage de calcaires de Ban Horn-. DepratJ. 1914 (Gothlandian); Saurin E., 1956 (D₂e); Hệ tầng Sinh Vinh (part.): Dovjikov A.E. et al, 1965 (O₃-S₁); Nguyễn Xuân Bao et al., 1969 (O₃-S₁ - Điệp)-, Trần Văn Trị et al, 1977 (O₃-S - Điệp). Các trầm tích Silur thượng-. Nguyễn Hữu Hùng et al. 1988

Lithology and Thickness

Limestone, marly shale. Stratotype on Da River bank; is over 750 m thick: (1). Dark grey marly shale and siltstone; 50 m thick, with brachiopods and bivalves. (2). Dark-grey limestone containing poorly preserved rugose ("coral") with thin interbeds of of light-grey shale; 250 m thick. (3) Dark grey limestone and clayey limestone interbedded with sandy limestone and calcareous siltstone; 350 m thick. (4). Dark-grey limestone interbedded with grey, greenish-grey clayey limestone and marl, and with some interbeds of conglomerate; 120 m thick. Hoa binh – Tu Ly section is mainly marly shale interbedded with limestone; 900 m thick.

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

Conformably rests on the underlying Sinh Vinh Fm.

Upper contact

Conformably overlain by the Song Mua Fm.

Regional extent

Distributed in the Muong Te, Hoa Benh- Tu Ly, Yen Lap, etc. areas situated on the lower coarse of the Song Da (Da River).

GeoJSON

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Fossils

Contains Brachipods, Bivalves and Rugose: Retziella weberi, Tadschikia xuanbaoi, Scoliopora sp., Favosites kunjakensis, Squameofavosites ex gr. bohemicus Iridistrophia aff. praeumbraculum, Orbiculoidea sp., Retziella weberi, Modiomorpha brevis, Modiolopsis sp., Orbiculoidea sp., Strispirifer sp., Schellwienella sp., Lingula sp., Camarotoechia aff. nucula (Nguyen Vinh 1977)..

[Figure: Bó Hiềng Fm (S_3-4 bh): Silurian: Brachiopods Retziella weberi; (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

[Figure: Bó Hiềng Fm (S_3-4 bh): Silurian: Tabulate Favosites banhomensis, (2 images) (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

Ludlow-Pridoli age from the paleontological basis and stratigraphic relationships.

Age Span:

Beginning stage:

Gorstian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

426.74

Ending stage:

Pridoli

Fraction up in the ending stage:

1.0

Ending date (Ma):

419.00

Depositional setting

Brachiopods and bivalves from the lower member of the Bo Tao - Tien Ban stratotype indicate the Late Silurian age. Rugose corals found at the base of member 2 are poorly preserved, Tabulates from the middle and upper parts of member 3 are mainly endemics, but corals have been recognized as close to Silurian species.

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).