Unit Name: Lea Park Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: early Campanian (83.5 - 80.6 ma)
Province/Territory: Alberta; Saskatchewan
Originator: Allan, 1918, p. 91-3.
The area around Lea Park, Alberta. The type section is a 25 m (82 ft) outcrop (McKellar, 1977) in the northeast corner of 15-11-54-3W4M.
The Lea Park is a westward thinning wedge with a reported thickness of 152 m (500 ft) (Williams and Burk, 1964) in the west-central Alberta Foothills in the type area Nauss (1947) indicated a thickness of 213 to 244 m (700 to 800 ft), further east the formation can exceed 270 m (886 ft) in thickness. The Lea Park is distributed over most of west-central Saskatchewan and central and southern Alberta as far west as the Disturbed Belt in the foothills. The northward limit is defined by the present day erosional edge which trends west-northwest through northwestern Saskatchewan and northeastern Alberta. The name Lea Park is applied eastwards only as far as the overlying Judith River Formation can be recognized, which is approximately a line running north-south through central Saskatchewan. To the south, in Montana the shale continues as the Judith River, Clagett and Eagle formations, and in southern Alberta the formation terminates where the Milk River sandstone is present. Meijer Drees and Myhr (1981) identified the Alderson Member of the Lea Park in the area transitional to the Milk River Sandstone.
The Lea Park Formation is typically composed of medium to dark grey shale with minor amounts of silt. Stringers of very fine-grained, tan colored sand and numerous layers of calcite veined clay-ironstone concretions are found throughout the formation. Thin bentonite seams are interspersed throughout; some have a wide geographic distribution. Abundant foraminiferal and molluscan faunas indicate an Early Campanian age.
The top of the unit is defined by an interfingering contact with the Judith River Formation. The bottom is the contact with the upper or First White Speckled Shale. In eastern Saskatchewan and southern Manitoba the Lea Park correlates with the Gammon Ferruginous, Pembina and lower Millwood members of the Pierre Shale. To the north the Labiche Formation of the Athabasca River region is partly equivalent. In the Peace River area the Puskwaskau Formation is of similar age to the lower Lea Park. In the north and central Alberta Foothills the Nomad, Chungo and Hanson members of the Wapiabi Formation are considered equivalent. In southern Alberta the Belly River, Pakowki and Milk River formations and in northern Montana their stratigraphic equivalents the Judith River, Claggett and Eagle formations are of similar age to the Lea Park.
Allan, 1918; McKellar, 1977; Meijer Drees and Myhr, 1981; Nauss, 1947; Williams and Burk, 1964.
Allan, J.A., 1918. Sections along North Saskatchewan River and Red Deer and South Saskatchewan rivers; Geological Survey of Canada, Summary Report 1917, Part C, pp. 9-13.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: R.L. McKellar; D.H. McNeil
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 May 2008