The Cairn Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...

(

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during th ...

) age in 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 ...

. It was named for the Cairn River near its junction with the Southesk River in

Jasper National Park Jasper National Park is a national park in Alberta, Canada. It is the largest national park within Alberta's Rocky Mountains spanning . It was established as a national park in 1930 and declared a UNESCO World Heritage Site in 1984. Its locatio ...

by D.J. McLaren in 1955.McLaren, D.J. 1955. Devonian formations in the Alberta Rocky Mountains between the Bow and Athabasca Rivers. Geological Survey of Canada, Bulletin 35. The Cairn Formation is stratigraphically equivalent to the

Leduc Formation The Leduc Formation is a Stratigraphy, stratigraphic unit of Late Devonian (Frasnian) Geochronology, age in the Western Canadian Sedimentary Basin, Western Canada Sedimentary Basin. It takes its name from the city of Leduc, Alberta, Leduc, and it w ...

, which is a major oil-producing formation in

central Alberta Central Alberta is a region located in the Canadian province of Alberta. Central Alberta is the most densely populated rural area in the province. Agriculture and energy are important to the area's economy. Geography Central Alberta is bordere ...

. Like the Leduc Formation, it was deposited in

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...

environments and is highly

fossiliferous 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 ...

.Shields, M.J. and Geldsetzer, H.H.J. 1992. The MacKenzie margin, Southesk-Cairn carbonate complex: depositional history, stratal geometry and comparison with other Late Devonian platform-margins. Bulletin of Canadian Petroleum Geology, vol. 40, no. 3, p. 274-293.Bloy, G.R., Hunter, I.G. and Leggett, S.R. 1984. Depositional environments of the Devonian Cairn Formation, Rocky Mountain front ranges, Canmore, Alberta. Carbonates in subsurface and outcrop: 1984 CSPG Core Conference, Canadian Society of Petroleum Geologists, p. 148. Extensive

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

s of the Cairn Formation near

Canmore, Alberta Canmore is a town in Alberta, Canada, located approximately west of Calgary near the southeast boundary of Banff National Park. It is located in the Bow Valley within Alberta's Rocky Mountains. The town shares a border with Kananaskis Country ...

are a popular

field trip A field trip or excursion is a journey by a group of people to a place away from their normal environment. When done for students, as it happens in several school systems, it is also known as school trip in the UK, Australia, New Zealand and ...

destination for those wishing to learn about Devonian reefs. They are also popular with

rock climbers Rock climbing is a sport in which participants climb up, across, or down natural rock formations. The goal is to reach the summit of a formation or the endpoint of a usually pre-defined route without falling. Rock climbing is a physically and ...

who enjoy the challenges presented by their extremely irregular surfaces.

Lithology

The Cairn Formation was originally deposited as

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

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 (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

s in

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

reef environments, and was extensively

dolomitized Dolomitization is a geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in another carbonate mineral, calcite. It is common for this mineral alteration into dolomite to take place due to e ...

during later

diagenesis Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a ...

. It now consists primarily of buff to dark grey, very fine to medium grained crystalline

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 ...

with good intercrystalline, biomoldic and

vug A vug, vugh, or vugg ( ) is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity (folding and faulting) are partially filled by quartz, ...

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

. Most of it is classified as

floatstone Floatstone is a type of carbonate rock. The original Dunham classification (Dunham, 1962) of limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed ...

, with stromatoporoids and other fossils supported in a dolomite matrix.Bloy, G.R., Leggett, S.R. and Hunter, I.G. 1989. The lower Fairholme reef complex (Cairn Formation), White Man Gap area, Canmore, Alberta. In: Reefs, Canada and adjacent areas. Canadian Society of Petroleum Geologists, Memoir 13, p. 399-402. The Cairn also includes minor amounts of undolomitized limestone and

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

Paleontology

Bulbous stromatoporoids are particularly common in the Cairn Formation and were the main reef-building organism.Cairn Formation
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org There are also tabular stromatoporoids, ''Amphipora'',

horn coral The rugosa, also called the tetracorallia or horn coral, are an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas. Solitary rugosans (e.g., '' Caninia'', '' Lophophyllidium'', '' Neoza ...

tabulate coral Tabulata, commonly known as tabulate corals, are an order of extinct forms of coral. They are almost always colonial, forming colonies of individual hexagonal cells known as corallites defined by a skeleton of calcite, similar in appearance to ...

s such as ''Thamnopora'',

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

and

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...

.Noble, J.P.A. 1970. Biofacies analysis, Cairn Formation of the Miette reef complex (Upper Devonian), Jasper National Park, Alberta. Bulletin of Canadian Petroleum Geology, vol. 14, no. 4, p. 493-543. The organisms are commonly either in growth position or have only been moved short distances. Some stromatoporoids show evidence of

bioerosion Bioerosion describes the breakdown of hard ocean substrates – and less often terrestrial substrates – by living organisms. Marine bioerosion can be caused by mollusks, polychaete worms, phoronids, sponges, crustaceans, echinoids, and ...

by boring

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

Thickness and distribution

The Cairn Formation typically ranges from to in thickness. It occurs in outcrop in the front and main ranges of 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 ...

from Kakwa Lake in northeastern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

to south of the

Bow River The Bow River is a river in Alberta, Canada. It begins within the Canadian Rocky Mountains and winds through the Alberta foothills onto the prairies, where it meets the Oldman River, the two then forming the South Saskatchewan River. These w ...

in Alberta. It is also recognized in the subsurface in some areas.Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba, p. 223-224. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. .

Relationship to other units

The Cairn Formation rests conformably on the Flume Formation, which is considered to be the lower member of the Cairn Formation in some areas, and it is overlain by the Peechee Member of the Southesk Formation. At reef margins the Cairn may interfinger with the Perdrix Formation which was deposited in deeper water, off-reef environments. The Cairn Formation is equivalent to, but not contiguous with, the lower

which lies farther to the east in

. It is also equivalent to the Cooking Lake Formation in

, and to the lower Duperow Formation and possibly the upper Souris River Formation in the

Williston Basin The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, southern Saskatchewan, and south-western Manitoba that is known for its rich deposits of petroleum and potash. The basin is a ...

. Its relationship to units in the

Crowsnest Pass Crowsnest Pass (sometimes referred to as Crow's Nest Pass, french: link=no, col du Nid-de-Corbeau) is a low mountain pass across the Continental Divide of the Canadian Rockies on the Alberta–British Columbia border. Geography The pass i ...

area of

southern Alberta Southern Alberta is a region located in the Canadian province of Alberta. In 2004, the region's population was approximately 272,017.outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

at Grassi Lakes, near

, Canada. File:Rock climbing on the Cairn Formation at Grassi Lakes, Alberta..JPG,

Rock climbing Rock climbing is a sport in which participants climb up, across, or down natural rock formations. The goal is to reach the summit of a formation or the endpoint of a usually pre-defined route without falling. Rock climbing is a physically and ...

on the Cairn Formation at Grassi Lakes. File:Stromatoporoid reef, Cairn Formation (Devonian).jpg, Cairn Formation stromatoporoid reef displayed in

Calgary Calgary ( ) is the largest city in the western Canadian province of Alberta and the largest metro area of the three Prairie Provinces. As of 2021, the city proper had a population of 1,306,784 and a metropolitan population of 1,481,806, makin ...

References

{{Western Canadian Sedimentary Basin, Canadian Rockies=yes Geologic formations of Alberta Devonian Alberta Devonian southern paleotropical deposits Frasnian Stage Dolomite formations Limestone formations Tidal deposits Western Canadian Sedimentary Basin Fossiliferous stratigraphic units of North America Paleontology in Alberta

Lithology

Paleontology

Thickness and distribution

Relationship to other units

See also

References