Unit Name: Belly River Formation
Unit Type: Lithostratigraphic
Age Interval: Santonian - Campanian (85.8 - 70.6 ma)
Province/Territory: Alberta; Saskatchewan
Originator: Dawson, 1883, p. 8B; 1884.
Named from exposures along the Belly and Bow rivers. Dawson (1884, p. 70c to 76c) referred specifically to exposures on the Belly River from the mouth of the St. Mary River (Twp. 8, Rge. 22W4M) downstream to the vicinity of the confluence of the Belly (now Oldman) and Bow rivers (Twp. 11, Rge. 13W4M). These may be taken as typical exposures.
In its restricted sense the Belly River is confined to the southern Alberta Foothills from the International Boundary to about the Clearwater River. Thicknesses of 900 to 1,300 m (2,952 to 4,264 ft) are reported. The name is often used in the plains region, where it generally refers to the interval between the Pakowki or Lea Park formations. It may be found anywhere in the region from the International Boundary to about 53° 30'N and as far east as 104° W in eastern Saskatchewan. It generally thins to the east from the values given above for the foothills to a depositional edge in Saskatchewan. Except for the westernmost edge, thicknesses in the plains rarely exceed 350 m (1,148 ft).
Predominantly interbedded mudstones to very fine-grained sandstones with subordinate, but prominent coarser grained sandstone beds. Bentonite, coal and concretionary beds are minor constituents. The dominant colors are shades of grey and green. A predominantly sandstone unit is present in the basal 10 to 30 m (33 to 98 ft), generally very fine- to medium-grained, with an overall upward increase in grain size. Some cross-bedding is usually present. Above, thick to massive sandstones are the most prominent lithology. These are fine- to very coarse-grained, with minor conglomerate, and usually are abrupt based and exhibit an upward decrease in grain size. Between are thick sequences of interbedded finer clastics, well-indurated to unconsolidated, open with abundant carbonaceous debris. These more recessive beds often constitute a large proportion of the entire section.
Overlies the Wapiabi Formation gradationally and is overlain abruptly but conformably by the Bearpaw Formation. To the north, in the foothills the Belly River is equivalent to a lower part of the Brazeau Formation. The Milk River, Pakowki and Judith River (or Oldman and Foremost) formations are lateral equivalents in the plains.
The name Belly River was applied to the sequence of sediments between the Pierre Shale (now Bearpaw Formation) and "lower dark shales of Rocky Spring Plateau" (now Colorado Group). However, it is now clear that Dawson miscorrelated the latter with shale exposures along the Milk River of what is now the Pakowki Formation. Thus, in the southern Alberta Plains Belly River was used as a group name to encompass the Pale beds, Foremost, Claggett and Milk River formations by Dowling (1916, 1917b), but confined to beds above the Pakowki and below the Bearpaw by Williams and Dyer (1930). Russell (1940) discontinued use of Belly River in the southern Alberta Plains in favor of Oldman and Foremost formations. This usage was followed by Irish (1971). McLean (1971) found that the distinction of the Oldman from Foremost was not clear or consistent and proposed that the name Judith River Formation, which has precedence be applied to the undivided sequence between the Pakowki and Bearpaw formations. The names Belly River and Oldman, which had been applied in western Saskatchewan and east central Alberta were also replaced by the name Judith River, thus unifying the nomenclature throughout southern Alberta and Saskatchewan wherever the overlying Bearpaw and the underlying Pakowki or Lea Park formations could be recognized. The name Belly River Formation has been applied in the southern Alberta Foothills to the undivided sequence from the Wapiabi Formation to the Bearpaw Formation, including Judith River, Pakowki and Milk River equivalents. The Pakowki is not recognized in the foothills, rendering the Judith River and Milk River indistinguishable. This usage has been consistent and is widely accepted. Usage of the term Belly River Formation in the plains has been fraught with confusion and should be discontinued.
Raised to Belly River Group in the Foothills of Alberta (Jerzykiewicz and Norris, 1994), and replaced by the Judith River, Oldman and Foremost formations in the plains of Alberta and Saskatchewan (McLean, 1990; Jerzykiewicz and Norris, 1994).
McLean, 1977b; Russell, 1970; Shaw and Harding, 1949; Stott, 1963; Williams, 1956.
Dawson, G.M., 1883. Preliminary report on the geology of the Bow and Belly river region, Northwest Territory, with special reference to the coal deposits. Geological Survey of Canada, Report of Progress for 1880-81-82, Part B.
Dawson, G.M., 1884. Report on the region in the vicinity of Bow and Belly rivers, Northwest Territory. Geol. and Nat. Hist. Surv. and Museum Can., Rept. Progress 1882-8344, Part C, p. 1-169.
Dowling, D.B., 1916. Water Supply, Southeastern Alberta (Contains Geological Map 1604); Geological Survey of Canada, Summary Report 1915, pp. 102-110.
Dowling, D.B., 1917b. Southern plains of Alberta; Geological Survey of Canada, Memoir 93, 200 p.
Irish, E.J.W., 1971. Geology, Southern Plains of Alberta, West of Fourth Meridian; Geological Survey of Canada, "A" Series Map 1286A, Scale: 1:500 000, NTS 72E, 72L, 72M, 82H, 82I, and 82P.
Jerzykiewicz, T. and Norris, D.K., 1994, Stratigraphy, structure and syntectonic sedimentation of the Campanian 'Belly River' clastic wedge in the southern Canadian Cordillera, Cretaceous Research, v. 15, p. 367-399.
McLean, J. R. 1990. Paskapoo Formation, p. 480-481. In D. J. Glass (ed.); Lexicon of Canadian Stratigraphy, Volume 4, Canadian Society of Petroleum Geologists, Calgary.
McLean, J.R., 1971. Stratigraphy of the Judith River Formation in the Canadian Great Plains. Saskatchewan Res. Counc., Geol. Div., Rept. 11.
McLean, J.R., 1977b. Lithostratigraphic nomenclature of the Upper Cretaceous Judith River Formation in southern Alberta; Philosophy and Practice. Bull. Can. Petrol. Geol., v. 25, p. 1105-1114.
Russell, L.S., 1940. Stratigraphy and structure. In: Geology of the southern Alberta Plains, Russell, L.S. and Landes, R.W. (Eds.). Geological Survey of Canada, Memoir 221, pp. 1-12B.
Russell, Loris S., 1970. Correlation of the Upper Cretaceous Montana Group between southern Alberta and Montana; Canadian Journal of Earth Sciences = Journal Canadien des Sciences de la Terre, vol. 7, no. 4 (August), pp. 1099-1108.
Shaw, Ernest William and Harding, Stanley Russell Lauck, 1949. Lea Park and Belly River formations of east-central Alberta; American Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 33, no. 4 (April), pp. 487-499.
Stott, D.F., 1963. The Cretaceous Alberta Group and equivalent rocks, Rocky Mountain Foothills, Alberta. Geol. Surv. Can., Memoir 317.
Williams, C.K., 1956. The Belly River Formation; Alberta Soc. Petrol. Geol., 6th Ann. Field Conf. Guidebook, p. 120-124.
Williams, M.Y. and Dyer, W.S., 1930. Geology of southern Alberta and southwestern Saskatchewan; Geological Survey of Canada, Memoir 163.
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; P.H. Davenport
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 23 Nov 2010