The Ma Butte Formation is a

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

unit of

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

) age in the

Western Canada Sedimentary Basin The Western Canada Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary ba ...

. It was named for Ma Butte, a mountain north of

Coleman, Alberta Coleman is a community in the Rocky Mountains within the Municipality of Crowsnest Pass in southwest Alberta, Canada. It was formerly incorporated as a town prior to 1979 when it amalgamated with four other municipalities to form Crowsnest Pas ...

, by J.R. McLean in 1980. It is present in the foothills of southwestern Alberta and it contains plant fossils.Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. .

Stratigraphy and lithology

The Ma Butte Formation is a unit of the

Blairmore Group The Blairmore Group, originally named the Blairmore Formation, is a geologic unit of Early Cretaceous age in the Western Canada Sedimentary Basin that is present in southwestern Alberta and southeastern British Columbia. It is subdivided into fo ...

. It consists primarily of fine-grained

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s interbedded with

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

s. Some coarser grained sandstones and conglomerate beds are also present. Beds of

bentonite Bentonite ( ) is an Absorption (chemistry), absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelli ...

and

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

increase upward toward the contact with the overlying

Crowsnest Formation The Crowsnest Formation, also called the Crowsnest Volcanics, is a geological formation in southwestern Alberta, Canada, on the southwestern margin of the Western Canadian Sedimentary Basin, Western Canada Sedimentary Basin. It was named for the Cr ...

. The sandstones of the Ma Butte Formation are

quartzose Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical fo ...

, in contrast with the feldspathic sandstones of the underlying Beaver Mines Formation.

Distribution and thickness

The Ma Butte Formation is present in the southern foothills of Alberta as far north as the

Red Deer River The Red Deer River is a river in Alberta and a small portion of Saskatchewan, Canada. It is a major tributary of the South Saskatchewan River and is part of the larger Saskatchewan / Nelson River, Nelson system that empties into Hudson Bay. T ...

. It has a maximum reported thickness of near the

Bow River The headwaters of the Bow River in Alberta, Canada, start at the Bow Glacier and Bow Lake (Alberta), Bow Lake in Banff National Park in the Canadian Rockies, Canadian Rocky Mountains. The glacial stream that feeds Bow Lake (Alberta), Bow Lake ...

Depositional environment and paleontology

The sediments of the Ma Butte Formation were derived from erosion of mountain ranges to the west, transported eastward by river systems, and deposited in a variety of floodplain environments. They include angiosperm (flowering plant)

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

, in contrast to the underlying Beaver Mines Formation. This marks the first appearance of angiosperms in this area.

Relationship to other units

The Ma Butte Formation is also known as the Mill Creek Formation. It disconformably overlies the Beaver Mines Formation. It is conformably overlain by the Crowsnest Formation in the south and the contact between the two is gradational. It is disconformably overlain by the Blackstone Formation in the north, and it is correlative with the Bow Island Formation to the east.

References

{{reflist Geologic formations of Alberta Cretaceous Alberta Albian Stage Sandstone formations of Canada Siltstone formations of Canada Mudstone formations of Canada Tuff formations of Canada Western Canadian Sedimentary Basin Conglomerate formations of Canada