The Atoka Formation along the southwestern margin of the Arkoma basin in Coal and Pontotoc Counties, Oklahoma, is predominantly a mudstone unit interbedded with thin (30 ft or 9 m), horizontally stratified sandstones and rare, thin, sandy limestones. The Atoka was deposited primarily during a marine transgression on a shallow shelf that received minor amounts of sand-size sediment. The sandstones present were deposited as the foreshore and shoreface parts of beach, barrier-bar, and/or longshore bar sand sequences during brief still-stands or minor regressions.
The Clarita anticline was a rising, positive structural element during Atoka deposition. A thickened Atoka sequence is present north of this feature and overlaps and thins onto and across it. This was unrecognized in previous fusulinid studies which infer that Fusulinella occurs 100 ft (30 m) above Profusulinella when the actual stratigraphic separation is over 1,000 ft (300 m). Movement of the Clarita anticline, an eastward extension of the Hunton anticline, indicates that the Arbuckle Mountains, were first beginning to undergo structural uplift in early Atoka time.
The multistory Atoka sandstones, with updip pinch-out and overlapping mudstones, can be stratigraphic traps for small hydrocarbon accumulations in the subsurface on the flanks of the Clarita anticline.