The McAlester basin was a geosynclinal trough through the Atokan and Desmoinesian epochs. Later history is obscure and the trough seems not to have been geosynclinal. There was a narrow platform area in the Atokan, a moderate one in early Desmoinesian, and an extremely broad and stable platform during the remainder of Desmoinesian time. A few of the outstanding characteristics are the following.

Atoka basinal sediments are shallow-water, fine-grained clastics, with little preserved fossil life, virtually no coal, and rapid changes in grain size and thickness.

Atoka platform sediments are rich in carbonates, occur in a belt less than 100 miles wide, and reach maximum thickness of 350 feet.

Des Moines basinal sediments were deposited in swamps and in shallow marine water. Unlike those of some basinal sequences, the units have great continuity and relatively small lateral change in thickness and grain size.

Des Moines platform sediments are cyclical and have remarkable continuity of units, excepting most sandstones. Many of the coal beds and such thin units as the Doneley limestone, Tiawah limestone, and Verdigris limestone can be traced over much of the platform and some can be recognized far into the basinal area.

During the Upper Pennsylvanian the basin was only weakly geosynclinal, and its history is that of a dying paleogeographic element.

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