Unit Name: Ma Butte Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Albian (112 - 99.6 ma)
Age Justification: Contains a prominent dicotyledonous (angiosperm) flora distinct from that in the underlying Beaver Mines Formation.
Province/Territory: Alberta
Originator: McLean, 1980.
Type Locality:
East face of Ma Butte, north of Coleman, in the Crowsnest Pass, southwestern Alberta. (Sec. 17 and 18, Twp. 9, Rge. 4W5M).
Distribution:
The type section is 120 m (394 ft). Reported thicknesses to the north, toward the Bow River range from 70 to 132 m (230 to 433 ft). To the north the formation thins and is absent north of the Red Deer River. Usage of the term is confined to the foothills and the westernmost edge of the adjacent plains.
Locality Data:
Thickness(m): Typical 120.
Lithology:
Predominantly interbedded mudstone, siltstone and very fine grained sandstone, with subordinate tuff and bentonite beds which increase in abundance upward. Coarser grained sandstones with some conglomerate beds are conspicuous features in outcrop. They are quartzose, in contrast to the feldspathic sandstones of the underlying Beaver Mines Formation. Colors are shades of greenish grey, olive-grey and purple to red.
Relationship:
Overlies the Beaver Mines Formation abruptly and disconformably. Overlain gradationally by the Crowsnest Formation in the southernmost foothills, and abruptly and disconformably by the Blackstone Formation (Sunkay Member) to the north. To the east it correlates with the Bow Island Formation. There are no equivalent beds in the central and northern foothills of Alberta.
History:
Introduced for the lower part of the now obsolete Mill Creek Formation when the Crowsnest Formation was removed from it (McLean, 1980).
Other Citations:
Douglas, 1950; Mellon, 1967; Norris, 1964.
References:
Douglas, R.J.W., 1950. Callum Creek, Langford Creek and Gap map-areas, Alberta. Geological Survey of Canada, Memoir 255.
McLean, J.R., 1980. Lithostratigraphy of the Lower Cretaceous coal-bearing sequence, Foothills of Alberta; Geological Survey of Canada, Paper 80-29.
Mellon, G.B., 1967. Stratigraphy and petrography of the Lower Cretaceous Blairmore and Mannville groups, Alberta Foothills and Plains; Res. Counc. Alberta, Bulletin 21.
Norris, D.K., 1964. The Lower Cretaceous of the southeastern Canadian Cordillera; Bulletin of Canadian Petroleum Geology, vol. 12, Field Conf. Guidebook issue, pp. 512-535.
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