Dunvegan Formation

Dunvegan Formation Stratigraphic range: Cenomanian ~99–94 Ma PreЄ Є O S D C P T J K Pg N ↓
Dunvegan Sandstone
Type	Geological formation
Underlies	Smoky Group
Overlies	Fort St. John Group (Shaftesbury Formation)
Thickness	up to 380 feet (120 m)[1]
Lithology
Primary	Sandstone
Other	Shale
Location
Coordinates	[ ⚑ ] : 55°55′14″N 118°37′55″W / 55.92043°N 118.63203°W / 55.92043; -118.63203 (Dunvegan Formation)
Region	Northeast  British Columbia Northwest  Alberta
Country	Canada
Type section
Named for	Dunvegan, Alberta
Named by	George Mercer Dawson
Year defined	1881
Dunvegan Formation (Canada)

The Dunvegan Formation is a stratigraphical unit of Cenomanian age in the Western Canadian Sedimentary Basin.

It takes the name from the settlement of Dunvegan, Alberta, and was first described in an outcrop on Peace River near Dunvegan by George Mercer Dawson in 1881.^[2]

Lithology

The Dunvegan Formation is composed of marine, and deltaic sandstone with thin shale interbeds in the Peace River Country. East of Dunvegan, Alberta it is of marine origin, and in its western reaches in British Columbia it was deposited in a continental facies, where the sandstone becomes more conglomeratic. During Dunvegan time, a brackish water environment was present in the Wapiti River area and south of Grande Prairie, where the formation is porous.

Hydrocarbon production

The Dunvegan Formation had an initial established recoverable oil reserve of 9.9 million m³, with 3.1 million m³ already produced as of 2008.^[3] Gas reserves totaled 18.7 million m³, with 4.5 million m³ already produced.^[4]

Distribution

The Dunvegan Formation is 180 feet (50 m) thick in its type locality in Peace River Country and up to 380 feet (120 m) in the sub-surface of the Canadian Rockies foothills. It occurs south of Fort Nelson and the Liard River in north-east British Columbia, thins out south of the Peace River Country. South of the Athabasca River, the Dunvegan grades laterally into the Blackstone Formation.

The Dunvegan Formation is exposed in outcrop along and near the Peace River east of the foothills, in the Peace River Country and the Chinchaga area, as well as patches in north-western Alberta and south of the Caribou Mountains.

Relationship to other units

The Dunvegan Formation is conformably overlain by marine shales of the Kaskapau Formation in the Peace River Country and overlies conformably and transitionally the shale of the Fort St. John Group. The relationship between the Dunvegan and the overlying/underlying units is diachronous and the boundaries of the Dunvegan are placed at the first and last appearances of sandstone within the shale-dominated succession.^[5]

References

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