Unit Name: Peechee Member
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Frasnian (385.3 - 374.5 ma)
Province/Territory: Alberta; British Columbia
Originator: Belyea, H.R. and McLaren, D.J., 1957a. Section first described in Belyea, H.R. and McLaren, D.J., 1956.
White Man Gap, at the southeast end of Mount Rundle, 6.5 km (4.0 mi) west of Canmore, Alberta on the Spray Lakes reservoir road. Section measured on the north side of the pass (51 deg 04'N, 115 deg 25'W). Supplementary subsurface sections in the Bailey Olds No. 1, in 2-18-31-27W4M, between 2,471 and 2,621 m (8,108 and 8,600 ft) and California Standard Princess CPR 9-22-20-12W4M, between 1,219.5 and 1,347.5 m (4,001 and 4,421 ft).
The Peechee Member is present in Fairholme Group carbonate buildups of the Rocky Mountains from northern Jasper National Park to the Flathead area of southwestern Alberta and southeastern British Columbia. In the subsurface it is present south of Twp. 30 and also east of a line between Drumheller and Vermilion. The Peechee Member is between 60 and 200 m (200 and 656 ft) thick, but may reach 300 m (984 ft) in the Flathead area and 223 m (732 ft) at Coronation Mountain in the main ranges south of the Columbia Icefield. It is 61 m (201 ft) thick at the type section, 90 m (300 ft) thick in the Miette buildup and 150 to 200 m (500 to 650 ft) thick in the Ancient Wall buildup. The subsurface dolomite and evaporitic reference sections (Belyea and McLaren, 1957) are 150 m (492 ft) and 128 m (420 ft) thick respectively.
The surface Peechee Member generally consists of light grey, medium- to coarse-crystalline dolomite in massive to thick beds. A few thinner, darker and slightly argillaceous beds bearing relict traces of amphiporids may occur, particularly towards the base of the member. Toward the margins of carbonate buildups of the Fairholme Group the outcrop may exhibit circular cavities or vague, concentrically-laminated patches suggestive of bulbous stromatoporoids. Within a few buildups (e.g., Ancient Wall) the Peechee Member is largely undolomitized and is essentially a lime sand unit composed of peloid-intraclast wacke-, pack- and grainstones, with minor amphiporids, stromatoporoids and corals. Small bioherms are occasionally developed at some buildup margins (Mountjoy and Jull, 1978). In the subsurface the Peechee Member includes both massive dolomites at the shelf edge adjacent to the Ireton shale basin, and more restricted evaporitic sediments in the interior of the southern Alberta shelf. The massive dolomites appear lithologically equivalent to the surface outcrops while the evaporitic facies includes fine-crystalline anhydrite, and dolomite with interbedded anhydrite and thin shales.
The Peechee Member is the basal member of the Southesk Formation. Lithologically the Peechee Member is a peloid-skeletal lime sand unit which overlies the biostromal Cairn Formation. In some mountain sections the contact is easily distinguished by this lithologic and associated color change, while in others interbedding of Cairn and Peechee lithologies may occur over 5 to 30 m (16 to 98 ft) and placing of the "contact" is arbitrary. This relationship has prompted a formation versus facies debate over the use of the terms Cairn and Southesk (see Taylor, 1957, 1958; Belyea and McLaren, 1957b; Dooge, 1966), but the formations, with their constituent members have survived. In the Flathead area the Peechee overlies the Borsato Formation. The Peechee Member is overlain conformably or paraconformably by the Grotto or, rarely the Arcs Member Lateral relations at buildup margins have the Peechee Member interfingering with the Perdrix and also the basal Mount Hawk Formations (Mountjoy and Mackenzie, 1973; Mountjoy and Jull, 1978). Locally, at buildup margins of the Fairholme Group the Peechee may be overlain by Mount Hawk (e.g., Cripple Tongue) In the subsurface in the southern Alberta shelf the Peechee sharply overlies the Cairn Formation on the shelf and is generally overlain by the Grotto Member. To the north it is replaced by the Ireton Formation. In southern Alberta Peechee Member strata are also referred to the upper part of the Leduc. The Peechee Member is stratigraphically equivalent to the Grosmont Formation of northeastern Alberta, the upper Leduc Formation of central Alberta, the upper Duperow Formation of the Williston Basin and part of the Jefferson Formation of Montana.
The member is named after Mount Peechee, located south of Lake Minnewanka in Banff National Park. Belyea and McLaren (1957a) formally named and described three members of the Southesk Formation in a surface section published in 1956. The Peechee Member replaced the informal lower grey dolomite member previously used by these authors. Belyea and McLaren (1957a) also extended this nomenclature into the southern Alberta subsurface.
Belyea, 1958; Belyea and McLaren, 1956, 1957a, 1957b; Cuppold, 1976; Dooge, 1966; Mountjoy and Jull, 1978; Mountjoy and Mackenzie, 1973; Price 1964; Taylor, 1957, 1958.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: E.W. Mountjoy; M.P Coppold
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003