Mia Le Fm

Period:

Devonian

Age Interval:

mid-Early Devonian; D₁ml, (2, 3, 4)

Province:
Viet Bac

Type Locality and Naming

Upper formation in Song Cao Gr. Holostratotype: the Lung Co - Mia Le Section, from the Si Ka to the Mia Le villages; Dong Van area, Ha Giang Province (N= 23°18'; E= 105°18'). Deprat J. 1915.

Synonym: Sérìe de Mié-lé: Đeprat J. 1915 (Ordovicianien-Gothlandien); Jacob c., Bourret R. 1920 (Eifelien); Saurin E., 1956 (Eifelien). • Hệ íầng Mia Lé: Paris F., Ta Hoa Phuong, Baudu-Suire 1993 (Di pg-etn); Ta Hoa Phuong 1994 (Dipg); Tong Dzuy Thanh, Ta Hoa Phuong 1994 (Dipg); Tong-Dzuy Thanh, Janvier Ph. 1987 (Dipg); Tống Duy Thanh 1993 (Dipg), 0« Vũ Khóc et al) 2000. Điệp Mia Lẻ: Dương Xuân Hảo 1973 (D₂e); Dương Xuân Hảỏ et al. 1975 (D₂e), 1980 (D_1-2); Phạm Đình Long 1973 (D₂e); Đoàn Kỳ Thuỵ e( al. 1976 (D₁-D₂e); Hoàng Xuân Tình et al. 1976 (Dr D₂e); Đặng Trần Huyên 1979 (D^-em); Tống Duy Thanh et al. 1986, 1988 (D₁ pg); Vũ Khúc, Bùi Phú Mỹ et al. 1990 (Dị); Tống Duy Thanh, Janvier Ph. 1990 (D₁ pg); Trần Đức Lưong, Nguyễn Xuân Bao et al. 1994 (D₁). Eịfeỉien\ Bourret R. 1922 (part.); Saurin E. 1956; Vasilevskaia E.D. (in Dovjikov A.E. et al.) 1965 (bậc Eifelian); Trần Vãn Trị et al. 1977 (Các trầm tích Eifelian): Coblencéen - Eifelien: Tống Duy Thanh 1965,1967; Dương Xuân Hảo 1975 (DiC-D₂e).

Schistes dé Yen Lac\ Bourret R. í 922 (Eifelian); Saurỉn E. 1956 (Emsian). Série de Na Man'. Bourret R, 1922 (Eifelian), Saurin E. 1956 (Emsian). Tầng Yên Lạc-. Tổng Duy Thanh 1965 (DrD₂e), 1979 (D,pg), 1967 (D,-D₂e); Tống Duy Thanh et al 1986, 1988 (Hệ lớp - D₁pg). Bộc Eifel: Vasilevskaia E.D. (Dovjikov A.E. et al. 1965). Tầng V/ Mía Lé (part.): Dương Xuân Hảo J 965 (D₂e); Dương Xuân Hảo et al. 1968, 1973 (D₂e). Điệp Bản Rõm (part.); Phạm Đình Long et al. 1967 (D₂e). Hệ tầng Mường Chà: Tạ Hoàng Tinh 1971. Hệ tầng Bản Vàn (?), Hệ tầng Cao Vinh (?): Tạ Hoàng Tinh 1971 Hệ tầng Pia Phương (?): Nguyễn Kinh Quốc et al. 1977; Vũ Khúc, Bùi Phú Mỹ 1990 (part.).

Điệp Đại Thị: Phạm Đình Long et al. 1979 (D₂e); Vũ Khúc, Bùi Phú Mỹ et al. 1990 (D₁); Tống Duy Thanh (in Vũ Khúc et al.) (Hệ tầng) 2000. Diệp Sông Cầu (part.): Phạm Đình Long et al. 1968 (D₂e). Non Trần Văn Tri et al. 1964 (= Loạt Sông cầu - Lower Devonian). Hệ tầng Cốc Xô (?): Vasilevskaia E.D. (in Dovjikov A.E. et al. 1965). Điệp Lược Khiêu: Tống Duy Thanh et al. 1979, 1986, 1988 (D₁); Tống Duy Thanh (ỉ« Vũ Khúc et al. - Hệ tầng) 2000 (D₁)

[Figure: Mia Le-Si Phai Segment of Lung Cu – Ma Le geological section (outcrop photo) (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

[Figure: Lung Cu-Mia Le: Geological map (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Lithology and Thickness

Siltstone, then mainly marly clay - (1). Greenish-grey siltstone interbedded with clay shale and marl, 50 m thick; containing brachiopods Euryspirifer tonkinensis and Eurysp. aff. parasensis. (2). Shale interbedded with marly shale, with some thin interbeds of clayey limestone in the uppermost part, 450 m thick; containing an abundance of fossils (brachiopods, rugose, bryozoan, fishes). The thickness» of the formation in the stratotype reaches about 500 m.

[Figure: Mia Lé – Bac Bun – Si Ka Fms: Stratigraphic Column (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Lithology Pattern:

Shallow-marine marl

Relationships and Distribution

Lower contact

Rests conformably upon clay shale of the Bac Bun Fm (Ha Giang Prov.), or the Na Ngan Fm (Ca Bang Prov; widespread in East Bac Bo).

Upper contact

Conformably below the Si Phai Fm (Ha Giang Prov.) or the Na Quan Fm (Ca Bang Prov)

[Figure: Mia Le-Si Phai Segment of Lung Cu – Ma Le geological section (outcrop photo) (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Regional extent

Largely distributed in the East Bac Bo region. Stratotype is in Ha Giang Province; but this facies is found in both southern South China and northern Viet Nam.

GeoJSON

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Fossils

The collected fossils are abundant, including Brachiopods Euryspirifer tonkinensis, Dicoelostrophia annamitica, Atrypa aff. reticularis, Elymospirifer kwangsiensis, Howellella crispa, Schellwienella cf. douvillei, S. lantenoisi, Athyrisl tiaomachiensis, Parachonetes zeili, Undispirifer aff. pseudoaculiatus, Howittia sp.; Coral Hardophylluml brancai; Bryozoan Fenestella sp.; Trilobite Proetus sp.; Bivalve Pterinea mieleensis; Vertebrates of Galeaspida, Placodermi.

[Figure: Mia Lé Fm: Tabulate Fossils (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

[Figure: Mia Lé Fm: Coral Fossils (thin sections) (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

[Figure: Mia Lé Fm: Brachiopods at Ma Le village, Lung Cu – Ma Le geological sectionƯ (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]

Age

Pragian

Age Span:

Beginning stage:

Pragian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

412.40

Ending stage:

Pragian

Fraction up in the ending stage:

1.0

Ending date (Ma):

410.51

Depositional setting

The sediments containing the Euryspirifer tonkinensis Assemblage in East Bac Bo are typical continental shelf facies.

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).