<Tr> <Th> Named by </Th> <Td> J.W. Nordquist, 1953 </Td> </Tr> <Tr> <Td_colspan="2"> Map of Bakken Formation reservoirs in the US portion of the Williston Basin (Saskatchewan is north border). Prior to 2007, most oil came from the Elm Coulee Oil Field . </Td> </Tr> <P> The Bakken Formation / ˈbɑːkən / is a rock unit from the Late Devonian to Early Mississippian age occupying about 200,000 square miles (520,000 km) of the subsurface of the Williston Basin, underlying parts of Montana, North Dakota, Saskatchewan and Manitoba . The formation was initially described by geologist J.W. Nordquist in 1953 . The formation is entirely in the subsurface, and has no surface outcrop . It is named after Henry Bakken, a farmer in Tioga, North Dakota, who owned the land where the formation was initially discovered, during drilling for oil . </P> <P> Besides the Bakken formation being a widespread prolific source rock for oil when thermally mature, significant producible oil reserves exist within the rock unit itself . Oil was first discovered within the Bakken in 1951, but past efforts to produce it have faced technical difficulties . </P>

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