Ngoc Lam Fm
Period:
Devonian
Age Interval:
Frasnian-early Famennian, D3fr nl, (18)
Province:
North Trung Bo
Type Locality and Naming
Lithology and Thickness
Lithology Pattern:
Chert
Relationships and Distribution
Lower contact
The Ngoc Lam Fm conformably rests on the underlying sandstone of the Dong Tho Fm.
Upper contact
Conformable below the overlying limestone of the Xom Nha Fm (D3 xn),
Regional extent
In the Hoa Son, Cat Dang areas, In the Cao Quang area
GeoJSON
{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[105.83,17.87],[106.14,17.93],[106.34,17.89],[106.57,17.76],[106.78,17.38],[106.71,17.12],[106.64,17],[106.35,17.01],[106.03,17.09],[105.8,17.29],[105.75,17.66],[105.83,17.87]]]]}}
Fossils
Brachiopod Calvinaria cf. megistanus, Conodont Palmatolepis subrecta
[Figure: Ngọc Lâm Fm: Conodonts Palmatolepis subrecta (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]
Age
Frasnian
Age Span:
Beginning stage:
Frasnian
Fraction up in beginning stage:
0.2
Beginning date (Ma):
377.34
Ending stage:
Frasnian
Fraction up in the ending stage:
0.9
Ending date (Ma):
371.88
Depositional setting
The high content of rare earths and the presence of conodonts prove that the formation was deposited in the deep marine environment similar to the Bang Ca (D1fr be), and Toe Tat (D3 - C1/i) formations in the North, and the Xom Nha Fm (D3;tn) in this area.
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).