The Plio-Miocene sediments of the Gulf Coast and the Atoka sediments of the Arkoma basin represent similar stratigraphic sequences deposited in quite different tectonic settings. The Plio-Miocene units are associated with the orogenically placid Gulf Coast geosyncline. The pattern of deposition has been development of load-produced basins (depocenters) during cyclic offlap. The Atokan units are associated with the Ouachita orogeny and represent shelf and trough suites. Certain aspects of these stratigraphic sequences are comparable with the modern sediments of the northwestern Gulf of Mexico.

The depositional patterns of the Plio-Miocene and the Atokan sedimentary prisms reflect structural-sedimentation interrelationships. In each prism, flexure zones demark abrupt thickening of the sedimentary units. The Atokan sediments were deposited on more competent sub-strata than were the Plio-Miocene sediments so that fewer major flexures developed. The depositional axis of the Atoka probably was tectonically controlled (a facies scarp) and the depositional axis of the Plio-Miocene (if properly located) was determined by sedimentary processes.

The Plio-Miocene and the Atoka have other features in common. Each is very predominantly clastic, represents a new area of maximum sediment accumulation in the depositional basin, and displaced a carbonate-shale facies. Prograding deltaic facies dominate the depositional environments but cyclic deposition is a prominent aspect of the sedimentation. Both the Atoka and the Plio-Miocene thicken at comparatively rapid rates and attain greater thicknesses than the associated older and younger sediments.

Kuendig (1959) has suggested that geosynclines should be classified by structural configuration, not sedimentary content. However, the similarities of the Plio-Miocene and the Atoka indicate that sedimentary patterns reflect source areas, transport and depositional processes, and topography. They do not reflect the structure of the catchment basin.

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