Shaunavon Formation

The Shaunavon Formation is a stratigraphical unit of Bathonian age in the Western Canadian Sedimentary Basin.

Shaunavon Formation
Stratigraphic range: Bathonian
↓
TypeGeological formation
Sub-unitsUpper Shaunavon
Lower Shaunavon
UnderliesSawtooth Formation
OverliesGravelbourg Formation
Thicknessup to 48 metres (160 ft)[1]
Lithology
PrimaryLimestone
OtherSandstone, shale
Location
Coordinates49.464°N 107.514°W / 49.464; -107.514 (Shaunavon Formation)
RegionWCSB
Country Canada
Type section
Named forShaunavon, Saskatchewan
Named byR.L. Milner and G.E. Thomas, 1954

It takes the name from the town of Shaunavon, and was first described in the Tidewater A.O. Eastend Crown No. 1 well, drilled south-west of the settlement, by R.L. Milner and G.E. Thomas in 1954.[2]

Lithology

The Shaunavon Formation is composed of two members. The lower member consists of buff microcrystalline massive limestone in the lower part with an oolitic bed at the top. The upper member consists of calcareous sandstone and oolitic limestone, shell coquina and argillaceous limestone with interbeds of gray and green shale. [1] Dolomitisation can occur in both members. Lenticular beds separated by sedimentation breaks are common in the upper member. Channels also occur in the upper Shaunavon.

Hydrocarbon production

Oil is produced from the Shaunavon Formation in south-western Saskatchewan.

Distribution

The Shaunavon Formation reaches a maximum thickness of 48 metres (160 ft).[1] It occurs in the sub-surface in south-western Saskatchewan. In the Williston Basin it appears present in Montana and North Dakota as the lower part of the Sawtooth Formation and Piper Formation. East of Weyburn, it grades into the shaley facies of the Melita Formation of Manitoba.

Relationship to other units

The Shaunavon Formation is conformably overlain by the Sawtooth Formation and conformably overlays the Gravelbourg Formation.[1]

It is equivalent to the Sawtooth Formation in southern Alberta, as well as to the Bowes member and Firemoon Member of the Piper Formation in Montana.

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References
  1. Lexicon of Canadian Geologic Units. "Shaunavon Formation". Retrieved 2010-01-01.
  2. Milner, R.L. and Thomas, G E., 1954. Jurassic System in Saskatchewan. In: Western Canada Sedimentary Basin American Association of Petroleum Geologists, p. 250-267
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