The Eagle Plain basin is an intermontane structural depression, 120 by 60 miles, which straddles the Arctic Circle in the Yukon Territory, Canada. Geologic history was influenced by a mildly positive central core which was flanked by local depositional basins through most of post-Cambrian time. Paleozoic basins include the Richardson basin, the area of the present southern Richardson Mountains, a Late Devonian basin west of the Richardson Mountains in the northeast, and a prominent Permo-Pennsylvanian area of depression in the southeast. Depositional topographic profiles identified in Permo-Pennsylvanian seismic record sections suggest shoreline conditions north of the present erosional limit of the Pennsylvanian, indicating increasingly positive behavior of the central c re during the late Paleozoic.

Regional uplift during the Triassic hiatus culminated in the development and erosion of the Eagle arch, which plunged gently northeast through the stable core. Late Jurassic and Early Cretaceous sands onlapped the area from the north. Not until Albian time, when a depositional trough along the present Dave Lord ridge linked the northern Richardson Mountains to the Kandik basin of the Alaska border region, did Mesozoic seas inundate the Eagle arch and the southern Eagle Plain. Laramide deformation of the mountain belts and the concurrent development of simple folds in the enclosed Eagle Plain basin were the final acts in a Mesozoic diastrophic cycle, during which pressure from the Yukon stable block in the northwest at first fostered and later crushed the Kandik-Richardson trough again t the stable Eagle Plain.

Exploratory drilling has been directed mainly toward the testing of the folded subcrop of Permo-Pennsylvanian sandstone, and the lower Paleozoic carbonate reservoirs on major anticlines. Fourteen wells have been drilled, with the resultant discovery of one oil and two gas accumulations, all in Permo-Pennsylvanian rocks.

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