Three Forks Group#Subdivisions
{{Infobox rockunit
| name = Three Forks Group
| image =
| caption =
| type = Geologic group
| age = {{Fossil range|Famennian|Tournaisian|Famennian to Tournaisian}}
| prilithology = Dolomite, mudstone, shale
| otherlithology =
| namedfor = Three Forks, Montana
| namedby = A.C. Peale, 1893
| region = Western Canadian Sedimentary Basin, Williston Basin
| country = Canada, United States
| coordinates =
| unitof =
| subunits = Bakken Formation, Lyleton Formation, Big Valley Formation, Torquay Formation
| underlies = Madison Group
| overlies = Saskatchewan Group
| thickness = {{convert|35|m|ft|-1}} to {{convert|80|m|ft|-1}}
| extent =
| area =
| map =
| map_caption =
}}
The Three Forks Group is a stratigraphic unit of Famennian age in the Williston Basin.
It takes the name from the city of Three Forks, Montana, and was first described in outcrop near the city by A.C. Peale in 1893 (for the Three Forks Shale).Peale, A.C., 1893. The Paleozoic section in the vicinity of Three Forks, Montana. U.S G.S., Bull. 110, p. 9-56.
Lithology
The Three Forks Group is composed of dolomite, mudstone and bituminous shale.
{{Cite web
|url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?
|title = Three Forks Group
|author = Lexicon of Canadian Geologic Units
|accessdate = 2010-01-01
|url-status = dead
|archiveurl = https://web.archive.org/web/20090416121153/http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl
|archivedate = 2009-04-16
}}
=Hydrocarbon production=
In the subsurface of the Williston Basin, the Three Forks is referred to as the Three Forks Formation, which lies between the Birdbear Formation below, and the Bakken Formation above.US Geological Survey, [http://ngmdb.usgs.gov/Geolex/NewRefsmry/sumry_10854.html Three Forks], accessed 6 Jan. 2013.
Oil produced from the Three Forks Formation in the Williston Basin of North Dakota and south-eastern Saskatchewan is often included in production statistics with the overlying Bakken Formation. For instance, the Three Forks and Bakken were combined in estimates of potential production released by the United States Geological Survey on April 30, 2013. The estimate by the USGS projects that 7.4 billion barrels of oil can be recovered from the Bakken and Three Forks formations and 6.7 trillion cubic feet of natural gas and 530 million barrels of natural gas liquids using current technology.{{cite web |url=http://www.valleynewslive.com/story/22118577/north-dakota-oil-boom-getting-bigger |title=North Dakota Oil Boom Getting Bigger - Valley News Live - KVLY/KXJB - Fargo/Grand Forks |accessdate=2013-05-01 |url-status=dead |archiveurl=https://web.archive.org/web/20131029190609/http://www.valleynewslive.com/story/22118577/north-dakota-oil-boom-getting-bigger |archivedate=2013-10-29 }}{{cite news|title=Northern plains site has twice as much oil as previously thought, Interior says|url=https://www.washingtonpost.com/national/health-science/northern-plains-site-has-twice-as-much-oil-as-previously-thought-interior-says/2013/04/30/16e0a436-b1cf-11e2-9a98-4be1688d7d84_story.html|accessdate=May 1, 2013|newspaper=The Washington Post|date=April 30, 2013|author=Lenny Bernstein|quote=The doubling of the estimate resulted largely because of the first look at the Three Forks Formation in North Dakota, which the Geological Survey said contains 3.73 billion barrels of oil. Its reassessment of the Bakken Formation, which lies above Three Forks, showed 3.65 billion barrels, only a little more than a 2008 USGS estimate. The agency’s conclusion that the formations contain 6.7 trillion cubic feet of natural gas and 530 million barrels of natural gas liquids represented a tripling of previous estimates.}}{{cite web|title=National Assessment of Oil and Gas Fact Sheet Assessment of Undiscovered Oil Resources in the Bakken and Three Forks Formations, Williston Basin Province, Montana, North Dakota, and South Dakota, 2013|url=http://pubs.usgs.gov/fs/2013/3013/fs2013-3013.pdf|work=Fact Sheet 2013–3013|publisher=United States Geological Survey|accessdate=May 1, 2013|author=Stephanie B. Gaswirth |author2=Kristen R. Marra |author3=Troy A. Cook |author4=Ronald R. Charpentier |author5=Donald L. Gautier |author6=Debra K. Higley |author7=Timothy R. Klett |author8=Michael D. Lewan |author9=Paul G. Lillis |author10=Christopher J. Schenk |author11=Marilyn E. Tennyson |author12=Katherine J. Whidden |quote=Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered volumes of 7.4 billion barrels of oil, 6.7 trillion cubic feet of associated/dissolved natural gas, and 0.53 billion barrels of natural gas liquids in the Bakken and Three Forks Formations in the Williston Basin Province of Montana, North Dakota, and South Dakota.}}
Distribution
Subdivisions
Relationship to other units
The Three Forks Group conformably overlies the Saskatchewan Group and is disconformably overlain by the Madison Group.
It is equivalent to the sum of the Wabamun Group and Exshaw Formation in Alberta.
References
{{reflist}}
{{Western Canadian Sedimentary Basin|Saskatchewan=yes}}
Category:Geologic groups of North Dakota
Category:Geologic groups of Montana
Category:Geologic groups of Saskatchewan
Category:Carboniferous southern paleotemperate deposits