Unit Name: Yohin Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Tournaisian (359.2 - 345.3 ma)
Age Justification: Scarce pelmatozoans, sponge spicules, ostracodes and brachiopods. Palynomorphs are locally common.
Province/Territory: Northwest Territories

Originator: Harker, 1961

Type Locality:
West side of Yohin Ridge, immediately north of Jackfish Gap, 32 km (20 mi) west of Nahanni Butte, southwest District of Mackenzie (map 95G, 61° 06'N, 123° 55'W).

Reported occurrences restricted to the southern Mackenzie Mountains between about 60 deg 50'N and 61 deg 45'N, southwest District of Mackenzie. Its known thickness ranges between 0 and about 157 m (515 ft).

Locality Data:
Thickness(m): Minimum 0, Maximum 157.

Mainly silty sandstone and sandy siltstone, but shale and limestone are locally important. The sandstones and siltstones are chiefly slightly calcareous siliceous submature subchertarenites and the limestones are sandy intraclast-skeletal lime grainstones and packstones. Siltstone occurs throughout the Yohin and is the principal lithology in the type section; northeastward the proportion of sandstone and limestone increases. Much of the Yohin comprises turbidites, and the principal sedimentary structures are graded beds, ripple cross-bedding, horizontal laminations and sole marks; moreover, megascale intraformational truncation surfaces are locally common.

Northeast of the south Nahanni River it conformably overlies an unnamed Mississippian shale unit, and southwestward it conformably overlies and grades into the Besa River Fm. The Clausen Fm conformably overlies the Yohin. It corresponds to Unit 1 of Patton (1958), map-unit 5 of Douglas and D.K. Norris (1959) and map-unit 30 of Douglas and D.K. Norris (1960).

Other Citations:
Bamber et al., in prep; Douglas, 1976a; Douglas and D.K. Norris, 1959, 1960, 1977a, 1977b; Harker, 1961, 1963; Patton, 1958.

Douglas, R.J.W. and Norris, D.K., 1959. Fort Liard and La Biche map-areas, Northwest Territories and Yukon; Geological Survey of Canada, Paper 59-6, 23 p.
Douglas, R.J.W. and Norris, D.K., 1960b. Virginia Falls and Sibbeston Lake map-areas, Northwest Territories (95F and 95G); Geological Survey of Canada, Paper 60-19, 26 p.
Douglas, R.J.W. and Norris, D.K., 1977a. Geology - Sibbeston Lake, District of Mackenzie: Geological Survey of Canada, Map no. 1377A (1:250,000).
Douglas, R.J.W. and Norris, D.K., 1977b. Geology - Virginia Falls, District of Mackenzie: Geological Survey of Canada, Map no. 1378A (1:250,000).
Douglas, R.J.W., 1976a. Fort Liard, District of Mackenzie: Geological Survey of Canada, Map no. 1379A.
Harker, P., 1961. Summary account of Carboniferous and Permian formations, southwestern District of Mackenzie; Geological Survey of Canada, Paper 61-1, 9 p.
Patton, W.J.H., 1958. Mississippian succession in south Nahanni River area, Northwest Territories. In: Jurassic and Carboniferous of western Canada; Goodman, A.J. (Ed.). Amer. Assoc. Petrol. Geol., John Andrew Allan Memorial Volume, p. 309-326.

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: L.V. Hills; B.C. Richards
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Jan 2009