Unit Name: Eager Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Early Cambrian (542 - 513 ma)
Age Justification: Biostratigraphy (Schofield, 1922).
Province/Territory: British Columbia
Originator: Schofield, 1922.
Type Locality:
Midway between Cranbrook and Fort Steele, southeastern British Columbia (no section designated).
Distribution:
Exposed near 49 deg 30'N in the Purcell Mountains, between the Moyie and St. Mary faults and, directly across the Rocky Mountain Trench between the comparable Dibble Creek and Boulder Creek faults in the Hughes Range of the Rocky Mountains. The thickness of the Eager Formation is undetermined, but is greatest in the Purcell Mountains, where it is probably at least 1,000 m (3,280 ft) in western exposures.
Lithology:
A pelitic formation, composed predominantly of argillite with local shale, siltstone and limestone. It is not distinctly calcareous, but limy lenses and beds occur throughout. The argillites are mostly dark grey, but may be blue-grey or grey-green and locally reddish. The argillites commonly weather rusty; calcareous beds and lenses weather to lighter colors, commonly buff.
Relationship:
Overlies the Cranbrook Formation with apparent conformity. In the Purcell Mountains the strata are bounded upward by faults and the present erosion surface. Early Cambrian fossils occur at a number of localities, but no fossils have been found in the upper part of the apparent thickest section. In the Rocky Mountains the formation is succeeded by Middle Cambrian limestones and shales, with which it is in deformed and poorly exposed contact.
References:
Schofield, S.J., 1922. Relationship of the Precambrian (Beltian) terrain to the Lower Cambrian strata of southeastern British Columbia; Geological Survey of Canada, Museum Bulletin 35.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: G.B. Leech
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Dec 2008