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Cairn Formation

Cairn Formation
Stratigraphic range: Frasnian
Cairn Formation dolostone with bulbous stromatoporoids..JPG
Cairn Formation dolostone with bulbous stromatoporoids. The red pocket knife is 9 cm (3.5 in) long.
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°W / 52.633; -116.967 (Cairn Formation)Coordinates: 52°38′N 116°58′W / 52.633°N 116.967°W / 52.633; -116.967 (Cairn Formation)
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.


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