Early Pennsylvanian sediments exhibit the existence of a continental shelf in the sea progressively migrating northwestward in sympathy with subsidence of the Ouachita trough. This platform is defined on the northwest by an encroaching shoreline, on the southeast by a migrating flexure or hinge line. Littoral deposition, that is, barrier beaches, bars, lentils and general discontinuity prevailed in the sands over the shelf. Accumulation of commercial petroleum, whether in anticlinal or stratigraphic traps, is limited to the shelf. This condition is strong evidence of local origin, migration and accumulation of oil. The progressive migrating character of the shelf may be depicted by a series of isopach maps grouping the strata as follows: 1. Atoka and Hartshorne; 2. McAles er, Warner and Savannah ("Lower Cherokee"); 3. Boggy ("Middle Cherokee"); 4. Stuart, Thurman, Senora and Calvin ("Upper Cherokee").

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