Cairn Formation Stratigraphic range: Frasnian |
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Type | Formation |
Unit of | Fairholme Group |
Underlies | Southesk Formation |
Overlies | Flume Formation |
Thickness | Up to 180 metres (590 ft) |
Lithology | |
Primary | Dolostone |
Other | Limestone, chert |
Location | |
Coordinates | 52°38′N 116°58′W / 52.633°N 116.967°WCoordinates: 52°38′N 116°58′W / 52.633°N 116.967°W |
Region | Alberta |
Country | Canada |
Type section | |
Named for | Cairn River, Alberta |
Named by | D.J. McLaren, 1955 |
The Cairn Formation is a geologic formation of Late Devonian (Frasnian) age in the Western Canada Sedimentary Basin. It was named for the Cairn River near its junction with the Southesk River in Jasper National Park by D.J. McLaren in 1955.
The Cairn Formation is stratigraphically equivalent to the Leduc Formation, which is a major oil-producing formation in central Alberta. Like the Leduc Formation, it was deposited in reef environments and is highly fossiliferous. Extensive outcrops of the Cairn Formation near Canmore, Alberta are a popular field trip destination for those wishing to learn about Devonian reefs. They are also popular with rock climbers who enjoy the challenges presented by its extremely irregular surfaces.
The Cairn Formation was originally deposited as limestones and mudstones in intertidal to subtidal reef environments, and was extensively dolomitized during later diagenesis. It now consists primarily of buff to dark grey, very fine to medium grained crystalline dolostone with good intercrystalline, biomoldic and vuggy porosity. Most of it is classified as floatstone, with stromatoporoids and other fossils supported in a dolostone matrix. The Cairn also includes minor amounts of undolomitized limestone and chert.