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Dong Tho Formation

Dong Tho Fm

Period: 
Devonian

Age Interval: 
Givetian-Frasnian, D2gv-D3fr dt, (18)


Province: 
North Trung Bo

Type Locality and Naming

Passing through the Dong Tho Mountain (Dovzhikov eta l., 1965). Lang Sung refereance section (along the car road from Cai Rong to Dong Le)

Synonym: Hệ tầng Dông Thọ-. Marcichev A.M., Trail Đức Luơng (in Dovjikov A.E. vò nnk. 1965, 1971); Dương Xuân Hảo và nnk. 1968; Trần Tính và nnk. 1998 (Bân thảo 1979); Nguyễn Đức Khoa 1984; Nguyễn Đình Hòe 1985; Tống Duy Thanh và tmk. I98Ó; vo Khúc & Bùi Phú Mỹ và nnk, 1990; Nguyễn Hữu Hùng và nnk. 1995; Nguyễn Quang Trung và nnk. 1998 (Băn thảo 1984 - Điộp); Nguyen Văn Hoành, Phạm Huy Thông (Điệp) 1984. Các trầm tích Give/ (part.): Dương Xuân Hảo (in Trần Văn Tri và nnk. 1977). Hệ tầng Dộng Th&. Tống Duy Thanh 1993; Tống Duy Thanh và nnk. 1995


Lithology and Thickness

Sandstone and Claystone in reference section: (1). Dark grey, medium - grained sandstone, 160 m thick. (2). Grey sandstone interbedded with clayey shale, 90 m thick. (3). Light grey quartz sandstone and carbonaceous shale containing plant remains, 175 m thick. Lepidodendropsis sp. should be found in this carbonaceous shale member. (4). Dark grey carbonaceous shale and chcrt, 75 m thick


Lithology Pattern: 
Clayey sandstone


Relationships and Distribution

Lower contact

The Dong Tho Fm conformably overlies the Muc Bai Fm (D2gv mb); this conformable relation can be observed in many sections.

Upper contact

It conformably underlies the Ngoc Lam Fm cherty claystone.

Regional extent

Distributed in the Ngan Son Valley situated in the Hai Tinh and Quang Binh provinces.


GeoJSON

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Fossils

Atrypa reticulata, Spinulicosta Spinulicosta, Stropheodonta sp„ Schizophoria sp., bivalves Mytilarca sp., Nucula sp., and bryozoans Fenestella sp.


Age 

Givetian-Frasnian age from the fossil content

Age Span: 

    Beginning stage: 
Givetian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
380.82

    Ending stage: 
Frasnian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
377.34

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, 2nd edition; 2011; English edited by A. Boucot).