Unit Name: Mirage Point Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Middle Ordovician ? - Middle Devonian (471.8 - 385.3 ma)
Age Justification: Barren of fossils. Dating inferred from stratigraphic position, particularly its relationship to the Chedabucto Lake, La Martre Falls and Chinchaga formations.
Province/Territory: Northwest Territories
Originator: A.W. Norris, 1965; Belyea and A.W. Norris, 1962.
Type Locality:
Composite section of upper part of formation outcropping along west shore of North Arm of Great Slave Lake between Redrock Point in the north and Gypsum Point in the south; 61 deg 53' to 62 deg 10'N, 114 deg 35' to 115 deg 02'W.
Distribution:
Present in the southern and southwestern part of the Great Slave Lake area. About 55 m (180 ft) of beds of the upper part of the formation discontinuously represented in type area. Recorded thicknesses range from 18 m (58 ft) in the Briggs Rabbit Lake No. 2 well (60 deg 54'03"N, 118 deg 46'47"W) to 181 m (595 ft) in the Northwest Windy Point No. 1 well (61 deg 19'N, 115 deg 52'W).
Lithology:
Red beds of dolomite, dolomitic silty mudstone breccia, gypsiferous and sandy dolomite, shale, siltstone, gypsum, anhydrite and salt.
Relationship:
Transitionally overlies basal Paleozoic sandstone of the Old Fort Island Fm, or in places, nonconformably overlies Precambrian rocks. It is unconformably overlain by Devonian evaporites of the Chinchaga Fm. Tracing of this unit into the subsurface of the Great Slave Lake area indicates that it contains equivalents of the Lotsburg, Ernestina Lake and Cold Lake formations of the Lower Elk Point Subgroup (Meijer-Drees and Davies, 1976). Replaced to the northwest by Bear Rock Fm.
Other Citations:
Belyea and A.W. Norris, 1962; Meijer-Drees and Davies, 1976; A.W. Norris, 1965.
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: A.W. Norris; P.A. Monahan; D.W. Morrow
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003