Unit Name: Tamarack River Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Proterozoic I (2500 - 1600 ma)
Age Justification: The age of the formation cannot be older than that of the Archean basement underlying the Knob Lake Group, and can be no younger than the circa 1800 Ma Hudsonian Orogeny.
Province/Territory: Newfoundland & Labrador; Quebec

Originator: Ware and Wardle, 1979.

Type Locality:
Tamarack River area between Esker and Sims lakes, western Labrador (53° 45'N to 54° 00'N, 66° 25'W to 66° 05'W; NTS 23 G/16). Ware and Wardle (1979) defined the type section of the unit as the northwestern flank of the hill west of Sims Lake (53° 58'N, 66° 04'W). Ware (1980) has defined additional reference sections at 53° 55'N, 66° 07'W and 53° 50'N, 66° 05'W.

The estimated observable thickness of the formation is 400 m (Ware, 1980). This, however, is probably a minimum thickness. The Tamarack River Formation is restricted to the southern part of the South Central Labrador Trough between latitudes 53° 45'N and 54° 07'N.

Locality Data:
Thickness(m): Minimum 400.

Interbedded sequence of red arkose, red to grey algal (pisolithic) dolomite, and red to grey argillite. The environment of deposition was largely fluviable, varying to possible lacustrine or shallow marine.

The Tamarack River Formation overlies the Proterozoic I Menihek Formation of the Knob Lake Group, with both conformable and, locally, possible disconformable contacts. It is overlain with angular unconformity by the Proterozoic II Sims Formation. Refer to Knob Lake Group for detailed stratigraphy of the group.

The formation was first recognized and proposed by Ware and Wardle (1979) for rocks previously considered part of the Menihek Formation (Fahrig, 1967). Ware and Wardle (1979) initially included the Tamarack River Formation in the Proterozoic II Sims Group. With later work, however, it became apparent that the formation was of Proterozoic I age and the term Sims Group was abandoned (Ware, 1980). The formation is now recognized as the uppermost unit of the Knob Lake Group (Wardle, 1982).

Fahrig, W.F., 1967. Shabogamo Lake map-area, Newfoundland - Labrador and Quebec, 23 G E 1/2: Geological Survey of Canada, Memoir 354, 23 p.
Wardle, R.J., 1982. Geology of the south central Labrador Trough: Newfoundland Department of Mines and Energy, Mineral Development Division, Maps 825 (23 I, J, O), 826 (23 I, J) with legend and cross-sections.
Ware, M.J. and Wardle, R.J., 1979. Geology of the Sims-Evening Lake area, western Labrador (parts of 23 G/9, 16, 23 H/13) with emphasis on the Helikian Sims Group: Newfoundland Depart-ment of Mines and Energy, Mineral Development Division, Report 79-5, 22 p.
Ware, M.J., 1979. Geology of the Sims Lake-Evening Lake area, western Labrador, pp. 135-141: in R.V. Gibbons (ed.), Report of Activities for 1978; Newfoundland Department of Mines and Energy, Mineral Development Division, Report 79-1, 205 p.
Ware, M.J., 1980. Tamarack River Formation, Menihek Lake area, western Labrador, pp. 194-200: in C.F. O'Driscoll and R.V. Gibbons (eds.), Current Research; Newfoundland Department of Mines and Energy, Mineral Development Division, Report 80-1, 264 p.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 6, Atlantic Canada; G.L. Williams, L.R. Fyffe, R.J. Wardle, S.P. Colman-Sadd, Boehner, R.C. (editor)
Contributor: R.J. Wardle
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 17 Mar 2010