Exshaw Formation

Exshaw Formation
Stratigraphic range: Late Famennian to Middle Tournaisian
TypeGeological formation
Sub-unitsLower and Upper Exshaw
UnderliesBanff Formation
OverliesWabamun Formation, Kotcho Formation, Palliser Formation
Thicknessup to 50 metres (160 ft)[1]
Lithology
PrimaryShale
OtherSiltstone, limestone
Location
Coordinates51°05′29″N 115°09′29″W / 51.09139°N 115.15806°W / 51.09139; -115.15806 (Exshaw Formation)
Region Alberta
Country Canada
Type section
Named forExshaw, Alberta
Named byP.S. Warren, 1937[2]

The Exshaw Formation is a stratigraphic unit in the Western Canada Sedimentary Basin.[3] It takes the name from the hamlet of Exshaw, Alberta in the Canadian Rockies, and was first described from outcrops on the banks of Jura Creek north of Exshaw by P.S. Warren in 1937.[2] The formation is of Late Devonian (late Famennian) to Early Mississippian (middle Tournaisian) age as determined by conodont biostratigraphy, and it straddles the Devonian-Carboniferous boundary.[2][4]

The Exshaw strata were deposited in a marine setting during the Hangenberg event, an oceanic anoxic event associated with the Late Devonian extinction. The black shales of the Exshaw Formation are rich in organic matter and are one of the most important petroleum source rocks of the Western Canada Sedimentary Basin.[5]

  1. ^ Cite error: The named reference lexicon was invoked but never defined (see the help page).
  2. ^ a b c Warren, P.S., 1937. Age of the Exshaw shale in the Canadian Rockies. American Journal of Science, Series 5, volume 33, pages 454-457.
  3. ^ Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 13: Devonian Wabamun Group of the Western Canada Sedimentary Basin". Retrieved 2014-10-18.{{cite web}}: CS1 maint: multiple names: authors list (link)
  4. ^ Meijer Dries, N.C. and Johnston, D.I. 1996. Famennian and Tournaisian biostratigraphy of the Big Valley, Exshaw and Bakken Formations, southeastern Alberta and Southwestern Saskatchewan. Bulletin of Canadian Petroleum Geology, vol. 44, no. 4, p. 683-694.
  5. ^ Caplan, M.L. and Bustin, R.M. 1996. Factors governing organic matter accumulation and preservation in a marine petroleum source rock from the Upper Devonian to Lower Carboniferous Exshaw Formation, Alberta. Bulletin of Canadian Petroleum Geology, vol. 44, no. 3, p. 474-494.