The Sassenach Formation is a stratigraphic unit of Late Devonian (early Famennian) age. It is present on the western edge of the Western Canada Sedimentary Basin in the Rocky Mountains and foothills of Alberta. It consists primarily of mudstone, siltstone, and silty carbonate rocks, and was named for Mount Sassenach in Jasper National Park by D. J. McLaren and E. W. Mountjoy in 1962.
The Sassenach Formation was deposited near the beginning of the Fammenian stage of the Devonian, following the Frasnian–Fammenian extinction event.Geldsetzer, H.H.J., Goodfellow, W.D., McLaren, D.J. and Orchard, M.J. 1987. Sulfur-isotope anomaly associated with the Frasnian-Famennian extinction, Medicine Lake, Alberta. Geology, vol. 15, no. 5, p. 393-396.Wang, K., Geldsetzer, H.H.J., Goodfellow, W.D. and Krouse, H.R. 1996. Carbon and sulfur isotope anomalies across the Frasnian-Famennian extinction boundary, Alberta, Canada. Geology, vol. 24, no. 2, p. 187-191. It includes fossil conodonts.Wang, K. and Geldsetzer, H.H.J. 1995. Late Devonian conodonts define the precise horizon of the Frasnian-Famennian boundary at Cinquefoil Mountain, Jasper, Alberta. Canadian Journal of Earth Sciences, vol. 31, p. 1825-1834.
Lithology and thickness
The Sassenach Formation was deposited below wave base in an off-reef marine setting. It consists of silty to sandy mudstone and siltstone, with argillaceous to silty and sandy limestone and dolomite. It has a maximum thickness of about .
Distribution and relationship to other units
The Sassenach Formation is present in the Rocky Mountains and foothills of Alberta, extending from northern Jasper National Park to the North Saskatchewan River, and it has also been tentatively recognized in some areas farther south. It overlies the Southesk Formation or the Mount Hawk Formation, depending on the location. It is overlain by the Palliser Formation, and is laterally equivalent to the upper beds of the Alexo Formation.
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