The Tunnel Mountain Formation is a geologic formation that is present on the western edge of the

Western Canada Sedimentary Basin The Western Canadian 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 ...

in the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part ...

of western Alberta. Named after Tunnel Mountain near Banff, it was deposited during the

Early Pennsylvanian The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timescale, the younger of two period (geology), subperiods (or upper of two system (stratigraphy), s ...

sub-period of the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

period.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. .

Lithology and stratigraphy

The Tunnel Mountain Formation consists of quartzose sandstone,

interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...

with lesser amounts of

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomiti ...

sandstone in the lower part, and minor beds of quartzite in the upper part. In areas where they can be differentiated, the formation is subdivided into the three formations shown below in ascending order. Where they cannot be differentiated, the name Tunnel Mountain Formation is applied to the entire sequence.Stott, D.L. 1967. Stratigraphy of the lower Rocky Mountain Supergroup in the southern Canadian Rocky Mountains. Bulletin of Canadian Petroleum Geology, vol. 15, no. 2., p. 209. * Tobermory Formation: quartz- chert sandstone, very fine- to fine-grained, quartz and dolomite cement; rare cross-bedding; minor interbeds of sandy dolomite. * Storelk Formation: quartz-chert sandstone, very fine- to coarse-grained, quartz cement, typically massive, very rare cross-bedding. *

Tyrwhitt Formation The Tunnel Mountain Formation is a geologic formation that is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of western Alberta. Named after Tunnel Mountain near Banff, it was deposited during the ...

: quartz-chert sandstone, very fine- to fine-grained, quartz and dolomite cement, rare cross-bedding; minor interbeds of sandy dolomite.

Paleontology

The dolomite beds of the Tunnel Mountain sequence include scattered brachiopods and foraminifera.

Thickness, distribution, and relationship to other units

The Tunnel Mountain Formation is present in the front ranges of the

of western Alberta, and reaches a maximum thickness of about 200 metres (600 ft). It

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlies the Etherington Formation or the Todhunter Formation of the

Mississippian Mississippian may refer to: * Mississippian (geology), a subperiod of the Carboniferous period in the geologic timescale, roughly 360 to 325 million years ago *Mississippian culture, a culture of Native American mound-builders from 900 to 1500 AD ...

Rundle Group The Rundle Group is a stratigraphical unit of Mississippian age in the Western Canadian Sedimentary Basin. It takes the name from Mount Rundle (itself taking the name from Robert Terrill Rundle), and was first described in outcrops at the nort ...

, and is conformably overlain by the Late

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

Kananaskis Formation The Kananaskis Formation is a geologic formation that is present on the western edge of the Western Canada Sedimentary Basin in the southern Canadian Rockies of western Alberta. Named after the Kananaskis Range near Banff,Glass, D.J. (editor) 19 ...

. In areas where the Kananaskis is not present, it is unconformably overlain by the Permian

Ishbel Group The Ishbel Group is a stratigraphic unit of Permian age in the Western Canadian Sedimentary Basin. It is present in the Canadian Rockies of Alberta and British Columbia. First defined by A. McGugan in 1963,McGugan, A., 1963. A Permian brachiopod ...

References

* {{cite web, title= Fossilworks: Gateway to the Paleobiology Database, author= ((Various Contributors to the Paleobiology Database)), url= http://www.fossilworks.org/cgi-bin/bridge.pl?action=home, access-date= 17 December 2021 Western Canadian Sedimentary Basin Geologic formations of Alberta Carboniferous Alberta Sandstone formations of Canada Dolomite formations Quartzite formations

Lithology and stratigraphy

Paleontology

Thickness, distribution, and relationship to other units

See also

References