Unit Name: La Loche Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: PROBABLE Middle Devonian (397.5 - 385.3 ma)
Province/Territory: Alberta; Saskatchewan
Originator: Norris, A.W., 1963.
Type Locality:
Contact Rapids on the Clearwater River, 56 deg 45'N, 109 deg 30'W, northeastern Alberta.
Distribution:
The La Loche Formation is 1.5 m (5 ft) thick at Contact Rapids; 2.8 m (9 ft) at Stony Island (Twp. 122, Rge. 9W4M) on Slave River and 5.7 m (18.8 ft) on the east bank of Slave River south of Caribou Island. The unit is present in the subsurface of northeastern Alberta, northwestern Saskatchewan, infilling lows on the Precambrian surface. It reaches a thickness of 30 m (98 ft) in the Clearwater river area.
Lithology:
Regolithic, poorly sorted breccia; fine- to coarse-grained, white to medium brownish grey arkosic sandstones and conglomeratic sandstones, with thin interbeds of sandy mudstone toward the top; arkosic grit and edgewise conglomerates and silty grits with festoon bedding toward the top.
Relationship:
The La Loche Formation seems to be a reworked regolith lying on the Precambrian surface. It is overlain gradationally by the Chinchaga or Keg River formations in the Stony islands area; in the Clearwater area it is the equivalent of the Contact Rapids Formation, i.e., the basal transgressive red beds of the Elk Point Group.
Other Citations:
Craig et al., 1967; Norris, 1963.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: J.H. Craig; G.G. Phipps
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 21 May 2004