Unit Name: Liard Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Middle Triassic - Late Triassic (245 - 199.6 ma)
Province/Territory: British Columbia

Originator: Kindle, E.D., 1946.

Type Locality:
On an island in, and on the south bank of Liard River near Hades (Hell) Gate, northeastern British Columbia. NTS Map 94N/6 Grayling River. Alternate and more accessible localities displaying all facies of Liard Formation were provided by Pelletier (1963, 1964) and Gibson (1971).

Lithology:
Resistant weathering dolomitic to calcareous sandstone, calcareous and dolomitic siltstone, and lesser amounts of dolostone, and thin to medium beds of buff to grey weathering sandy to silty, bioclastic limestone. Between Peace and Pine rivers the limestone is very finely crystalline, less sandy and silty, and commonly cherty, weathering a distinct medium to dark grey. Elsewhere the Liard weathers pale to medium grey to yellowish grey. The Liard Formation contains the Middle Triassic index Nathorstites fauna. The Liard Formation varies in thickness from zero at Mount Ludington and Calnan Creek, where strata of the formation appear to have been removed by pre-Ludington erosion, to a maximum of 417.6 m (1,370 ft) at Clearwater Lake, south of the Williston Lake Reservoir. Near Liard River the formation attains a thickness slightly in excess of 182.9 m (600 ft) (McLearn and Kindle, 1950). It is recognized throughout the Rocky Mountain Foothills between the Liard and Pine rivers, northeastern British Columbia.

Relationship:
The Liard is unconformably overlain by the Cretaceous Garbutt and Buckinghorse formations in the Liard River area of the eastern foothills. Southward the Liard is gradationally overlain by yellowish brown to yellow, pale grey to orange-brown weathering dolomitic to calcareous sandstone, siltstone, sandy limestone, dolostone and minor amounts of intraformational and/or solution breccia of the Charlie Lake Formation. The Liard is gradationally overlain by darker grey weathering, finer grained siltstone and silty shale of the Toad Formation. Between Pine River and the Williston Lake Reservoir, the lower contact is placed where dark weathering siltstones, limestones and silty shales of the Toad grade vertically into paler grey weathering, coarser grained siltstone and very finely crystalline limestone of the Liard. The Liard is laterally equivalent to the subsurface Halfway Formation of the Peace River Plains, and the upper two thirds of the Llama Member of the Sulphur Mountain Formation of the Jasper-Banff area (Gibson, 1975). The Liard Formation includes strata mapped and/or interpreted as Halfway by Pelletier (1964) and Colquhoun (1962) in the foothills of the Peace and Muskwa River areas, and as part or all of the Mount Wright Formation as recognized by Colquhoun (1962) in the Halfway and Peace River (Williston Lake) areas.

History:
Originally included by Kindle (1944) as part of the Toad Formation in the Liard River area. In 1946 the unit was separated as a distinct formation and the name Toad retained for lower, more thinly bedded and finer grained beds. The facies was recognized and the name extended southward by Pelletier (1960, 1961, 1963, 1964) and Gibson (1971, 1975) to include all strata between the underlying Toad and overlying Charlie Lake formations in the foothills as far south as Pine River.

Remark:
Parent is Schooler Creek Group. Age in BC geological compilation is given as Triassic (K.Bellefontaine, A. Legun, N.W.D. Massey et al., 1995). Is this just a generalization, or is there a real age discrepancy?

Other Citations:
Colquhoun, 1962; Gibson, 1971, 1975; Kindle, 1944, 1946; McLearn and Kindle, 1950; Pelletier, 1960, 1961, 1963, 1964.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: D.W. Gibson
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 31 Mar 2006