Unit Name: Mount Head Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Visean (345.3 - 328.3 ma)
Province/Territory: Alberta; British Columbia

Originator: Douglas, 1953b.

Type Locality:
A type section has not been designated. The type area is the Mount Head map-area, NTS 82J/7 and 10, Rocky Mountain Foothills and eastern front ranges, southwestern Alberta (Douglas, 1958b; Macqueen and Bamber, 1968).

In the Rocky Mountains and foothills the Mount Head Formation extends from the United States border in southeastern British Columbia and southwestern Alberta to 55°15'N in east-central British Columbia (Oswald, 1964, Price, 1965; Macqueen and Bamber, 1968; Beauchamp et al., 1986; Richards et al., 1983). In the interior plains it occurs from the United States border in southwestern Alberta to 53°15'N. Farther north on the plains it lithologic and stratigraphic equivalents have been included in the Debolt Formation by Macauley et al. (1964); an arbitrary nomenclatural boundary separates the two. The Mount Head thickens southwestward overall, but its thickness is highly variable because of several episodes of subaerial erosion and a southwestward facies change to the Livingstone Formation. The Mount Head, over 300 m (984 ft) thick in the western front ranges, is principally between 75 and 250 m (246 and 820 ft) thick in the Rocky Mountains, and normally less than 75 m (246 ft) thick to the east (Douglas, 1958b; Price, 1965; Macqueen and Bamber, 1968).

Douglas (1958b) divided part of the Mount Head into the Wileman, Baril, Salter, Loomis, Marston and Carnarvon members. A seventh member, the Opal was erected by Macqueen and Bamber (1968). These members are widely distributed, but cannot be easily identified in most of the eastern Rockies from 51°45'N to 53°30'N, the central to eastern foothills and interior plains. Only the lower three members are present from 53°30'N to 55°15'N. The recessive, thin to medium bedded Wileman, which abruptly overlies the Turner Valley and Livingstone formations thickens from 7.6 m (25 ft) in the northeast to 25 m (82 ft) in the southwest, and is chiefly silty, microcrystalline dolostone with locally abundant small and medium scale crossbedding. Resistant, southwestward thickening deposits of the Baril unconformably overlie the Wileman and range in thickness from 11 to 39 m (36 to 128 ft). Pelletoid-skeletal and skeletal-ooid lime grainstone with subordinate dolostone constitute most of the medium- to very thick-bedded Baril, which commonly shows large scale cross-bedding. In western sections cherty, pelletoid-skeletal wackestone and packstone are common and become more abundant upward. The recessive Salter, thickening from 29 m (95 ft) in the northeast to 67 m (220 ft) in the southwest generally conformably overlies the Baril, but in the southwest it gradationally overlies the Livingstone Formation. Microcrystalline, silty dolostone, fenestral cryptalgal boundstone and foraminiferal-algal lime wackestone predominate in this thin to medium bedded unit. Skeletal and ooid lime grainstone are common in the southwest; anhydrite and related solution-collapse breccia are widespread in the northwest. Chert is very abundant in mixed-skeletal limestone at southwestern localities. In most areas the resistant, northeastward thinning Loomis is 30 to 101 m (98 to 331 ft) thick. It unconformably overlies the Salter and is predominantly massive, thick to very thick bedded lime grainstone. The Loomis, abruptly overlain by the Marston in the east is conformably overlain by the Opal in the west Deposits of the recessive, rhythmically bedded Marston pass southwestward into the lower Opal. The medium-bedded Marston consists of microcrystalline dolostone with subordinate fenestral, cryptalgal boundstone, solution-collapse breccias, ooid to skeletal limestone, shale and marlstone. The Opal thickens southwestward and is 161 m (528 ft) thick at its type locality. It overlies the Loomis, passes northeastward into the Marston and lower to middle Carnarvon, and is generally abruptly overlain by the upper Carnarvon in the southwest. The moderately resistant, medium- to very thick-bedded lower Opal consist of cross-bedded, pelletoid-skeletal and ooid-skeletal lime grainstone with subordinate marlstone and cherty, pelletoid-skeletal lime packstone and wackestone. The recessive, medium- to thick-bedded upper Opal comprises shale and marlstone rhythmically interbedded with fenestral cryptalgal boundstone, peloid-skeletal lime wackestone and packstone, and breccias. The resistant, medium- to thick-bedded Carnarvon conformably overlies the Marston in the northeast and abruptly overlies the Opal to the southwest. Peloid-skeletal lime wackestone to packstone, rhythmically interbedded with thin shale beds constitute the Carnarvon, which is unconformably overlain by the Etherington Formation. Most of the medium- to thick-bedded, undivided Mount Head comprises sparsely fossiliferous, yellowish grey silty dolostone. Shale, anhydrite, siltstone, solution-collapse breccias and dolomitized skeletal limes tone are commonly present. Chert nodules and irregular masses are plentiful in many units (Macqueen and Bamber, 1968; Bamber et al., 1981, McGugan, 1984).

The Mount Head abruptly overlies the Turner Valley Formation in the northeast at a contact that is locally a subaerial unconformity. To the southwest the Mount Head abruptly overlies the eastern Livingstone Formation. Farther southwestward the basal Mount Head becomes younger as its four lower members grade laterally basinward into the Livingstone (Macqueen and Bamber, 1968; Macqueen et al., 1972). The Mount Head is unconformably overlain by the Etherington Formation in most of the southern Rocky Mountains south of 52°30'N; and in part of the adjacent foothills, but the contact with the Etherington in the southwest may be partly conformable. East, northeast and northwest of the erosional edge of the Etherington, Permian and Mesozoic strata overlie the Mount Head (Richards et al., 1983).

Bamber, E.W., Macqueen, R.W., and Ollerenshaw, N.C., 1981. Mississippian stratigraphy and sedimentology, Canyon Creek (Moose Mountain), Alberta; in, Field guide to geology and mineral deposits, Thompson, R.I. and Cook, D.G. (Eds.), Calgary 1981 Annual Meeting; Geological Association of Canada (GAC), Mineralogical Association of Canada (MAC), Canadian Geophysical Union (CGU), pp. 177-194.
Beauchamp, B., Richards, B.C., Bamber, E.W., and Mamet, B.L., 1986. Lower Carboniferous lithostratigraphy and carbonate facies, upper Banff Formation and Rundle Group, east-central British Columbia, Project 810011; in, Current Research, Part A (Issued in two sections) (Pages 385-826), Stratigraphy; Geological Survey of Canada, Paper 86-1A, pp. 627-644.
Douglas, R.J.W., 1953b. Carboniferous stratigraphy in the southern Foothills of Alberta; Alberta Soc. Petrol. Geol., 3rd Ann. Field Conf. Guidebook, p. 66-88.
Douglas, R.J.W., 1958b. Chungo Creek map-area, Alberta (report and geologic map 6-1958) (Scale: 1 in. to 1 mile); Geological Survey of Canada, Paper No. 58-3, 45 p.
Macauley, G., Penner, D.G., Procter, R.M., and Tisdall, W.H., 1964. Carboniferous; In: Geological history of western Canada, McCrossan, R.G. and Glaister, R.P. (Eds.), p. 89-102. Alberta Soc. Petrol. Geol.
Macqueen, R.W. and Bamber, E.W., 1968. Stratigraphy and facies relationships of the Upper Mississippian Mount Head Formation, Rocky Mountains and foothills, southwestern Alberta; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 16, no. 3 (September), pp. 225-287.
Macqueen, R.W., Bamber, E.W., and Mamet, B.L., 1972. Lower Carboniferous stratigraphy and sedimentology of the southern Canadian Rocky Mountains. 24th Internat. Geol. Congress, Montreal, Quebec, Guidebook, Field Excursion C17.
McGugan, Alan, 1984. Carboniferous and Permian Ishbel Group stratigrapy, North Saskatchewan Valley, Canadian Rocky Mountains, western Alberta; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 32, no. 4 (December), pp. 372-381.
Oswald, D.H., 1964. Mississippian stratigraphy of southeastern British Columbia. Bull. Can. Petrol. Geol., Flathead Valley Guidebook issue, v. 12, p. 452-459.
Price, R.A., 1965. Flathead map-area, British Columbia and Alberta; Geological Survey of Canada, Memoir 336.
Richards, B.C., Bamber, E.W., Higgins, A.C. and Utting, J., 1993. Carboniferous, Chapter 4E. In: Sedimentary cover of the North American Craton: Canada; Stott, D.F. and Aitken, J.D. (Eds.). Geol. Surv. Can., v. 5, (also Geol. Soc. Amer., The Geology of North America, DNAG, v. D-1), p. 202-271.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: B.C. Richards
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 15 Nov 2012