Huoi Loi Fm

Period:

Devonian

Age Interval:

D_1-2hi, (16)

Province:
North Trung Bo

Type Locality and Naming

Western Nghe An Province. The section along Huoi Loi Stream and the car road parallell to the stream, from Muong Xen to Pa Khao areas, West Nghe An Province (E = 19°16'; E = 104°09').

Synonym: Điệp Huổi Lôi'. Nguyễn Văn Hoành et al. 1979; Nguyễn Vãn Hoành, Phạm Huy Thông 1984 (D ị. 2); Nguyễn Hữu Hùng 1981 (Hệ tầng); Nguyễn Đức Khoa 1984 (Hệ tầng); Tống Duy Thanh 1986, 1988 (Hệ tầng); Vũ Khúc và Bùi Phú Mỹ 1990(Hệ tầng);Nguyễn Hữu Hùng 1985 (Hệ tầ n g -D₁.2); Tống Dzuy Thanh 1993 (Fm- D₁. 2). Les complex de grès schisteux anthracolitiques (part.): Fromaget J. 1927. Trâm tích Paleozoi trung (part.): Mareichev A.M. và Trần Đức Lưcmg (in Dovjikov A.E. et al. 1965). Tầng Sóng Cả (part.): Lê Duy Bách et al. 1969 (S - D),

Lithology and Thickness

Claystone and fine-grained Sandstone. Stratotype is 650 m thick of: (1). Light grey, fine-grained, 5 - 20cm bedded, clean sandstone; upwards the scction includes blue grey, brown grey calcarcous-clayey shale, siltstone containing coral Calceola sandalina, brachiopods Euryspirifer sp., Howellella sp., Stropheodonta sp., Acrospirifer sp.; crinoid Hexacrinites humilicarinaius and indeterminable trilobite, 200 m thick. (2). Dark grey, blue grey, thin-bedded (l-3cm) clayey shale interbedded with siltstone, and ash grey limestone containing corals Favosites sp., Trachypora aff. circulipora, Thamnopora aff. kolodaensis, Coenites sp., Natalophyllum sp, Chaetetes yunnanensis, 120 m thick. (3). Dark grey clayey shale, siltstone interbedded with calcareous shale and blue grey limestone containing corals Squameofavosites sp., Striatopora sp. indct., Scoliopora sp., Cladopora sp., Heliolites sp., and indeterminable stromatoporoids, corals, 100 m thick. (4). Black, folded clayey shale interbedded with siltstone, sometimes sericitized siltstone, 80 m thick.

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Rests conformably on the Tay Trang Fm.

Upper contact

Conformably underlies the Nam Can Fm.

Regional extent

Restricted to Muog Xen area, west of Nghe An Province.

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[104.15,20.14],[104.45,20.08],[104.66,19.92],[104.89,19.82],[105.11,19.52],[105.2,19.21],[105.21,18.7],[104.93,18.6],[104.67,18.6],[104.22,18.79],[103.94,19.4],[103.99,19.82],[104.15,20.14]]]]}}

Fossils

Contains Favosites muongxenensis, Trachypora dubatolovi, Thamnopora cf. savis, Coenites quydatensis, Egosiella cf. safonoviensis, Trypanopora sp., Chaetetes cf. yunnanensis, Utaratuia cf.pinghuangshaensis, Fistulipora sp.,

[Figure: Huổi Lôi Fm: Tentaculites Homoctenus (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

Based on fossils, it has been dated as Emsian (late-Early Devonian) into Givetian (late-Middle Devonian).

Age Span:

Beginning stage:

Emsian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

410.51

Ending stage:

Givetian

Fraction up in the ending stage:

0.5

Ending date (Ma):

382.10

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Tong-Dzuy Thanh and Vu Khuc (editors, 2011); English edited by A. Boucot