Unit Name: Paskapoo Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Paleocene (65.5 - 55.8 ma)
Province/Territory: Alberta; Northwest Territories
Originator: Tyrrell, 1887.
Blindman River, a tributary entering the Red Deer River from the northwest, 10 km (6.25 mi) north of Red Deer, Alberta. An exact location was not specified (Paskapoo is a native word for blind man).
Only 240 m (787 ft) of strata are exposed in the type area. Elsewhere on the plains reported thicknesses range from zero to 600 m (1,968 ft). The formation thickens westward but no reliable thicknesses have been published. Estimates range up to 1,000 m (3,280 ft), but in certain areas the thickness may be much greater. The upper surface of the formation is almost always the present erosional surface, so that thickness values range from zero to some maximum, but have little interpretive value. The formation is confined to a crescent with its base along the foothills, the bottom near 50 deg N, the top at about 55° N and its outer edge extending out to 112° W at its most easterly limit.
Thickness(m): Minimum 0.
Interbedded hard to soft mudstone, siltstone and sandstone, with subordinate limestone, coal, pebble conglomerate and bentonite. Most prominent are thick (up to 15 to 20 m, 49 to 66 ft) abrupt based, massive to cross-bedded, medium- to coarse-grained, buff weathering sandstones Commonly fining-upward thinner, finer grained, well-indurated to unconsolidated sandstones occur throughout the formation. More abundant, but more recessive are soft mudstone to siltstone, usually grey to greenish grey in color. Coal seams are usually thin and dirty, but locally they are of economic interest, as in the Obed-Marsh area northeast of Hinton, Alberta. Limestone beds, reported from the plains are thin and argillaceous, but sometimes very fossiliferous. Conglomerate or conglomeratic sandstone is a minor but conspicuous component of some sections, particularly in the foothills. A conglomerate bed reported by Lang (1947) from High Divide Ridge (50-25W5) and estimated to be 485 m (1,492 ft) thick appears to be anomalous.
Overlies the Scollard Formation of the Edmonton Group in the plains, and the Coalspur Formation in the foothills abruptly, but opinions differ in whether this relationship is conformable or not (see Allan and Sanderson, 1945; Gibson, 1977b). The upper surface is usually the present erosional surface, but in a few localities the Paskapoo is overlain abruptly and disconformably by later Tertiary gravels (see Carrigy, 1971b). Laterally it is equivalent to an upper part of the Ravenscrag Formation in southern Saskatchewan.
Tyrrell (1887, p. 138) suggested that the contact of his Paskapoo with the underlying Edmonton beds represented the Tertiary/Cretaceous boundary. This time connotation to a lithostratigraphic unit has been a continuing problem. The name Paskapoo has been applied consistently in the central Alberta Plains region, except for Irish (1970) and Carrigy (1970), who lowered the basal contact with the Edmonton Group to the top of the Battle Formation, including the Scollard as a member. Gibson (1977b) returned the boundary to its original position and included the Scollard as a formation in his Edmonton Group. The name Paskapoo was introduced into the foothills by Russell (1932c). It has not been possible to correlate the strata directly from the type area, so that attempts were made to correlate on the basis of fossil age determinations. The base of the Paskapoo has been placed at different stratigraphic levels by different authors, from the top of the Brazeau to hundreds of metres above, and well above the main coal bearing zone. Recently, palynological analysis by Sweet (in: Jerzykiewicz and McLean, 1980) has shown that the coal bearing zone located approximately 250 m (820 ft) above the top of the Brazeau Formation is equivalent in age to the Ardley zone of the Edmonton Group in the plains. Therefore beds below this coal zone cannot be correlated with the type Paskapoo Formation. The base of the Paskapoo in the foothills has been placed at the base of the first prominent sandstone unit above the last major coal seam in the Coalspur Formation (Jerzykiewicz and McLean, 1980).
Allan, J.A. and Sanderson, J.O.G., 1945. Geology of Red Deer and Rosebud sheets, Alberta, Res. Counc. Alberta Rept. 13.
Carrigy, M.A., 1970. Proposed revision of the boundaries of the Paskapoo Formation in the Alberta Plains; Canadian Society of Petroleum Geologists, Bulletin of Canadian Petroleum Geology, vol. 18, no. 2 (June), pp. 156-165.
Carrigy, M.A., 1971b. Lithostratigraphy of the uppermost Cretaceous (Lance) and Paleocene strata of the Alberta Plains; Alberta Research Council, Edmonton, AB, Research Council of Alberta Bulletin 27, 161 p.
Eliuk, L.S., 1969. Correlation of the Entrance Conglomerate, Alberta, by palynology. M.Sc. thesis, Univ. Alberta.
Gibson, D.W., 1977b. Upper Cretaceous and Tertiary coal-bearing strata in the Drumheller-Ardley region, Red Deer River valley, Alberta, Geological Survey of Canada, Paper 76-35, 41 p.
Irish, E.J.W., 1970. The Edmonton Group of south-central Alberta; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 18, no. 2 (June), pp. 125-155.
Jerzykiewicz, T. and McLean, J.R., 1980. Lithostratigraphic and sedimentological framework of coal-bearing Upper Cretaceous-lower Tertiary strata, Coal Valley area, central Alberta Foothills; Geological Survey of Canada, Paper 79-12.
Lang, A.H., 1947. Brule and Entrance map-areas, Alberta; Geological Survey of Canada, Memoir 244.
Russell, L.S., 1932c. The Cretaceous-Tertiary transition of Alberta. Transactions of the Royal Society of Canada, Ser 3, v. 26, s. 4, p. 121-156.
Tyrrell, J.B., 1887. Report on a part of northern Alberta and portions of adjacent Districts of Assiniboia and Saskatchewan; Geological Survey of Canada, Ann. Rept.1886, new ser., v. 11, Part E, p. 1-176.
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.R. McLean
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 24 Nov 2010