Unit Name: Natla Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: early Eifelian - late Eifelian (397.5 - 391.8 ma)
Age Justification: Crinoids, tentaculids.
Province/Territory: Northwest Territories
Originator: Gabrielse et al., 1973.
Type Locality:
The type section is 14.5 km (9 mi) south of the Natla River and 4.8 km (3 mi) west of the Wrigley Lake map-area (63°14'N, 128°06'W).
Distribution:
It is 434 m (1,425 ft) thick at the type section and 444 m (1,455 ft) in the Nahanni map-area. The formation occurs in the Wrigley Lake map-area and to the west and in the Sekwi Mountain and Nahanni map-areas.
Locality Data:
Thickness(m): Typical 434.
Lithology:
Characteristically a recessive, thin-bedded, sooty-gray weathering limestone with resistant ribs of varying number and thickness. It can be subdivided into 3 informal units, listed in ascending order, in the type section: 1) 114 m (375 ft) resistant light grey weathering, medium-bedded to massive, behind massive fetid, coarse-grained crinoidal limestone; 2) 104 m (340 ft) of recessive medium- and thin-bedded medium to dark grey weathering, dark grey, very fine-grained limestone with four resistant light grey weathering ribs of coarse-grained crinoidal limestone; and 3) 216 m (710 ft) of recessive dark grey or sooty weathering thin-bedded, dark grey, fine-grained, fetid limestone.
Relationship:
The Natla Formation conformably overlies and interfingers with the Arnica and is conformably overlain by the Landry Formation. It is the lateral equivalent of the Grizzly Bear Formation and the upper part of the Funeral Formation.
References:
Gabrielse, H., Blusson, S.L., and Roddick, J.A., 1973. Geology of the Flat River, Glacier Lake and Wrigley Lake map-areas, District of Mackenzie and Yukon Territory; Geological Survey of Canada, Memoir 366 (Parts I and II), 421 p.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 2, Yukon Territory and District of Mackenzie; L.V. Hills, E.V. Sangster and L.B. Suneby (editor)
Contributor: M.P. Cecile; L.V. Hills
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 01 Dec 2010