Devonian   Time: 408 to 360 mya Duration: 48 million years   The oldest known coal beds in North America that may be suitable for future mining are bituminous in rank and located in the southwestern part of the Northwest Territories and in the Arctic islands of northern Canada. The late Devonian Speckty Kopf Formation in the eastern Pennsylvanian Anthracite region and correlative rocks in central Pennsylvania, western Maryland, and northern West Virginia in the Appalachian Coal Region contain thin, high-ash beds that appear to be non-commercial.

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