Unit Name: Cedar Lake Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: ? Wenlock (428.2 - 422.9 ma)
Province/Territory: Manitoba; Saskatchewan

Originator: Stearn, C.W., 1956.

Type Locality:
Cedar Lake region, approximately 70 km (44 mi) southeast of The Pas, Manitoba. No type section was designated. Subsequent flooding of the Grand Rapids forebay by Manitoba Hydro has drowned many of the outcrops noted by Stearn. Suggested reference core hole is Manitoba Core Hole M-4-78, Denbeigh Point, in 7-33-46-16WPM, between zero and 28.5 m (94 ft), immediately south of the type area.

In the Manitoba outcrop belt thicknesses range from about 30 m to 50 m (98 to 164 ft). Cedar Lake strata occur throughout the Manitoba outcrop belt and extend in the subsurface throughout the Williston Basin to their subcrop edges. Maximum thickness of the Cedar Lake in southern Saskatchewan, where overlain by Taylorton (upper Interlake) strata is approximately 100 m (328 ft).

Mostly very fine-grained to aphanitic dolomite, with thin wavy bedding. Fragmental dolomites, intraformational conglomerates and stromatolitic dolomites are present but are rare in contrast to the underlying East Arm Formation. Chert nodules are common near the top of the unit and fossils are sparse, although locally abundant in some beds. Local discontinuous subunits are the basal, highly crinoidal Cross Lake Member and an upper, reeflike coral stromatoporoid unit, the Chemahawin Member.

In the type area the Cedar Lake rests, with possible slight disconformity on the underlying Silurian East Arm Formation and is overlain with gentle angular unconformity by the Middle Devonian red shales of the Ashern Formation. In the deeper basin the Cedar Lake is disconformably (?) overlain by the Taylorton Formation (upper Interlake).

Originally defined in outcrop by Stearn (1956). King 119641 extended the unit into the subsurface and included in it "that portion of Stearn's East Arm Dolomite lying above the v marker".

Other Citations:
Haidl, 1987; Jamieson, 1979; Johnson and Lescinsky, 1986; King, 1964; Magathan, 1987; Porter and Fuller, 1959; Saskatchewan Geological Society, 1958; Stearn, 1956.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: H .R. McCabe; F.M. Haidl
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 11 May 2004