Bai Chay Fm

Period:

Permian

Age Interval:

Late Permian, bc (5)

Province:
East Bac Bo

Type Locality and Naming

Yen Ngua Hill, Bai Chay area, Western Ha Long City (former Hon Gai Town), between the Post Office and the Bai Chay Ferry (N = 20° 2' 40"; E = 107° 57’ 30").

Synonym: Tầngsilic Bãi Cháy: Nguyẽn Văn Liêm 1970 (P₂). Hệ tầng Bãi Cháy: Phạm Đồng Điột, Nguyễn Trung Châu 1973 (Tầng - P₂); Nguyễn Văn Liêm, Lê Hùng (in Dương Xuân Hảo et al. 1980); Nguyễn Công Lượng et al. 1980; Nguyễn Văn Liêm 1985. (P₂). Lê Hùng, Tống Duy Thanh et al. 1987. Grès et quarzites de Hongay. Lantenois H. 1907; Colani M. 1919 (Ouralo-Permien). Le facies schisto-greseux terminal du Permien: Patte E. 1927. Kazanien (part.): Saurin E. 1956. Tập silic lục nguyên và silic Permi thượng: Davjikov A.E. et al. 1965. Tầng Phù Lãng'. Nguyễn Quang Hạp 1967. Hệ tầng Hạ Long: Phạm Văn Quang et al. 1969 (P₂ - T₁). Tầng Thán Phún: Phạm Văn Quang el al. 1969. Thống Permi thượng: Lẽ Hùng in Trần Văn Trị et al. 1977. Diệp Dồng Đăng (Dông Bấc Băc Bộ): Vũ Khúc, Bùi Phú Mỹ et al. 1990 (P₂). Hệ tầng Đá Trắng: Lê Hùng et al 1994 (C₁)

Lithology and Thickness

Cherty sediments: Yen Ngua Hill in Bai Chay has 200 m of: (1). Grey, thin-bedded and massive chert, interbedded with dark grey calcareous chert and yellowish brown sandstone, 100 m thick. (2). Grey, slightly white weathering, thick-bedded and massive coarse quartz-rich sandstone, interbedded with grey, thin beds of chert and clayey chert, 100 m thick; with Wuchiapingian fossils.

Lithology Pattern:

Chert

Relationships and Distribution

Lower contact

Conformably rests upon the Da Mai Fm (= Bac Son Fm).

Upper contact

The section is unconformably covered by conglomerate and sandstone of the coal-bearing Hon Gai Fm.

[Figure: Hòn Gai Fm resting unconformably on the Bai Chay Fm (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Regional extent

The Bai Chay Fm occurs in the coastal zone of East Bac Bo in narrow, sublatitudinal trending bands on the limb margins of the Cam Pha - Hon Gai Syncline. The northern band extends from Quang La following Road N2 18B to Vu Oai; the southern band extends along the Quang Hanh - Cam Pha car road lying in the hilly zone south of Bai Chay Beach.

GeoJSON

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Fossils

In the calcareous chert of this member some Wuchiapingian bivalves have been collected by geologists of the Paleontological Laboratory (Institute of Geology and Mineral Resources), such as Guizhoupecten regular is, G. sp., Stutchburia aff. dianensis, Euchondria sinensis, Bakevellia sp.

Age

Wuchiapingian.

Age Span:

Beginning stage:

Wuchiapingian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

259.55

Ending stage:

Wuchiapingian

Fraction up in the ending stage:

1.0

Ending date (Ma):

254.24

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).