Unit Name: Baldonnel Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Carnian (228.7 - 216.5 ma)
Province/Territory: Alberta; British Columbia

Originator: Clark, 1957.

Type Locality:
Subsurface of the Peace River Plains, northeastern British Columbia in the Pacific Fort St. John No. 16 well in 2-18-84-19W6M, between 1,257.9 and 1,297.2 m (4,127 and 4,256 ft). Surface reference section at Brown Hill, on the north side of Williston Lake, 11-E/94-B-2 (Colquhoun, 1962).

Distribution:
The unit is recognized in exposures in the Rocky Mountain Foothills between the Sukunka and Liard rivers and in the subsurface of the Peace River Plains The Baldonnel attains a maximum recorded thickness of 146 m (479 ft) near the headwaters of the Eleven Mile Creek between Pine River and Williston Lake (Peace River).

Locality Data:
WELL 100021808419W602; SUNCOR FT ST JOHN 02-18-084-19. Thickness(m): Maximum 146. Interval(m): From 1257.9, To 1297.2.

Lithology:
Field exposures of the Baldonnel are divided into two lithofacies (Gibson 1971, 1975). The main or upper unit is recognized in the Rocky Mountain Foothills and Peace River Plains between the Liard and Sukunka rivers areas and comprises pale grey to brownish grey weathering, resistant, cliff forming limestone and dolostone, with lesser siltstone and very fine-grained sandstone. The lower unit, called the Ducette Member (Gibson, 1971) is confined to the area immediately adjacent to and between the Peace and Sukunka rivers and consists of dark grey-brown weathering, carbonaceous-argillaceous siltstone, very fine-grained sandstone, limestone and minor amounts of dolostone, which lithologically resembles strata of the Pardonet Formation. In the subsurface of the eastern foothills and Peace River Plains the Baldonnel consists predominantly of dolostone with well developed porosity and permeability, and in many areas forms a productive gas reservoir.

Relationship:
Part of the Schooler Creek Group, the Baldonnel is conformably overlain by thinly bedded, very dark grey weathering limestone and siltstone of the Pardonet Formation. Throughout most areas of the Peace River Plains and eastern foothills it is unconformably overlain by the Jurassic Fernie Formation. North of Peace River-Williston Lake and in the subsurface of the Peace River Plains the Baldonnel is conformably and gradationally underlain by medium grey dolostone, siltstone and limestone of the Charlie Lake Formation. Between Peace River-Williston Lake and Sukunka River the contact is abrupt and distinct and is placed where yellowish brown to pale grey weathering strata of the Charlie Lake contrast sharply with the overlying dark greyish brown weathering limestone and dolomitic siltstone of the Ducette Member of the Baldonnel Formation. The Baldonnel Formation is equivalent to the upper part of the 'Grey Beds' of McLearn (Pelletier, 1964), the upper part of the Ludington Formation to the north (Gibson, 1975), the Brewster Limestone, and most of the Winnifred members of the Whitehorse Formation of Alberta (Gibson, 1975).

History:
First described by Clark (1957) in the Peace River Plains subsurface for the dolostone unit capping the Triassic rock succession. Type section assigned by Hunt and Ratcliffe (1959) to the Pacific Fort St. John No. 16 well. Facies recognition and name extended by Colquhoun (1962), Pelletier (1964) and Gibson (1971) to include equivalent surface strata in the Rocky Mountain Foothills between the Muskwa and Sukunka rivers.

Remark:
Age given as Middle-Late Triassic in BC Geological compilation (Massey et al., 2005).

References:
Clark, L.M., 1957. Fort St. John sets pace for Peace River gas fields; Oil and Gas Journal, vol. 55, no. 33, pp. 132-144.
Colquhoun, D.J., 1962. Triassic stratigraphy in the vicinity of Peace River Foothills, British Columbia; in, 4th Annual Field Trip Guidebook; Edmonton Geololgical Society, pp. 57-88.
Gibson, D.W., 1971. Triassic Stratigraphy of the Sikanni Chief River-Pine Pass Region, Rocky Mountain Foothills, northeastern British Columbia; Geological Survey of Canada, Paper, 70-31, 105 p.
Gibson, D.W., 1975. Triassic rocks of the Rocky Mountain Foothills and Front ranges of northeastern British Columbia and west-central Alberta; Geological Survey of Canada, Bulletin 247, 42 p.
Hunt, Albin Digby and Ratcliffe, James Douglas, 1959. Triassic stratigraphy, Peace River area, Alberta and British Columbia, Canada; The American Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 43, no. 3 (March), pp. 563-589.
Massey, N.W.D., MacIntyre, D.G., Dejardins P.J. and Cooney R.T. (compilers), 2005. Digital Geology Map of British Columbia. British Columbia Ministry of Energy and Mines, Geological Survey Branch, open file 2005-2 (DVD).
Pelletier, B.R., 1964. Triassic stratigraphy of the Rocky Mountain Foothills between Peace and Muskwa rivers, northeastern British Columbia; Geological Survey of Canada, Paper 63-33.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: D.W. Gibson
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 23 Oct 2009