The McAlester-Arkansas Coal basin is an elongate arcuate basin in southeastern Oklahoma and northwestern Arkansas. It is bounded by the following: Mississippi embayment on the east, Ozark uplift on the north, Ouachita Mountains on the south, and Arbuckle Mountains on the west.

The stratigraphic sequence ranges from Cambrian through Pennsylvanian age with aggregate thicknesses of 2,000 feet of sediment along the northern rim of the basin to probably in excess of 25,000 feet in the southern part of the area. Paleozoic rocks of late Pennsylvanian age crop out over most of the area. The depositional axis has not been determined by drilling as yet. Geophysical methods may define the basin and clarify the relationship between the Arbuckle-Ozark type rocks and the Ouachita rocks.

Surface structures generally strike east-west and were formed by compressional forces from the south (Ouachita area) against the Ozark positive area on the north beginning in early Pennsylvanian time, and extending into the late Pennsylvanian. The effect of these forces is reflected by the amount of structural relief present; highly faulted structures occur south of the Choctaw fault, well defined structures north of the Choctaw fault, and gentler folds along the Arkansas River.

The basin has been the scene of exploratory work for many years with the greatest and best organized effort being carried out presently. Surface, subsurface, aerial photo interpretation, and geophysical mapping methods have been attempted. Monotonous sequences of sands and shales crop out, making surface work difficult. Rough terrane, poor accessibility, and hard drilling make seismic work expensive. Subsurface work will become increasingly important as more deep wells are drilled.

Gas prospects in Atoka and Morrow rocks are numerous, but a great volume of sediments both Pennsylvanian and pre-Pennsylvanian in age have not been evaluated.

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