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Eagle Plain Basin

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View towards west of the subdued topography of the Eagle Plain basin. Photograph is taken from the parking lot of the Eagle Plains hotel, at kilometer 369 of the Dempster Highway.

 

 

 

 

 

 

Eagle Plain, in north central Yukon, is an under explored sedimentary basin that consists of two subbasins, Bell in the north and Eagle in the south, separated by the east-west trending Eagle arch. Sedimentary strata attain a maximum thickness of 5800 m and can be divided into a Paleozoic succession unconformably overlain by a Mesozoic succession. Lower Paleozoic strata include carbonate sedimentary rocks of the Porcupine platform in the west and basinal shale associated with the Richardson trough in the east. Upper Paleozoic strata consist of siliciclastic rocks with lesser carbonate. Paleozoic strata are unconformably overlain by Cretaceous marine siltstone, shale and sandstone deposited in a developing foreland basin adjacent the Cordilleran orogen. In the northern part of the basin, Jurassic siliciclastic strata can be found unconformably between Paleozoic and Cretaceous sediments.

Evidence for petroleum systems in the Eagle Plain basin are plentiful, including the presence of hydrocarbon-bearing strata, source rocks, shows in drill stem tests of natural gas and crude oil from wells, and surface seepages of crude oil. Oil and gas bearing zones are found throughout the Eagle Plain stratigraphic succession in both structural and stratigraphic traps. Formations with proven oil reserves discovered in Eagle Plain include the Cretaceous Fishing Branch Formation; Permian Jungle Creek Formation;  Mississippian Hart River Formation (Canoe River and Chance Sandstone members). Formations with proven gas reserves include the Cretaceous Fishing Branch Formation; Permian Jungle Creek Formation; Mississippian Hart River Formation (Canoe River and Chance Sandstone members); Upper Devonian to Lower Mississippian Tuttle Formation; Devonian Ogilvie Formation; and Ordovician Bouvette Formation.

Source rocks can be found in both Paleozoic and Mesozoic strata including the Cambrian to Devonian Road River Group, Upper Devonian Canol Formation, Upper Devonian to Lower Mississippian Ford Lake Shale, Pennsylvanian Blackie and Ettrain formations, and Cretaceous Porcupine River, Mount Goodenough, and Whitestone River formations.

Oil-stained shale has been observed at the surface in Upper Devonian strata in the southern part of the basin. Oil-stains have also been observed in surface sandstone samples in the Upper Cretaceous Eagle Plain Group. Of interest is a Hart River Formation shale outcrop on the Eagle River that was observed to be burning during in spring 2008 presumably from the presence of hydrocarbons.

Thirty four wells have been drilled in the Eagle Plain basin, with the majority (22) drilled in the southern Eagle subbasin. Thirty three wells were drilled between 1958 and 1985, with one drilled in 2005. All oil and gas discoveries to date are found in the Eagle subbasin. In addition to well data, seismic data exist in the basin, some of which are available through the National Energy Board. In 2009, a regional airborne gravity and magnetic survey was completed over the Eagle Plain basin with over 45 400 line-km of data collected on east-west oriented lines at 800-m spacing.


Further Reading

Osadetz, K.G., Zhuoheng, C., and Bird, T.D., 2005. Petroleum Resource Assessment, Eagle Plain Basin and Environs, Yukon Territory, Canada, Yukon Geological Survey Open File 2005-2/Geological Survey of Canada, Open File 4922, 88 p.