Abstract

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 (less than 30 ft), 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 were deposited as the foreshore and shoreface portions of beach, barrier bar and/or longshore bar sand sequences during brief stillstands or minor regressions.

The Clarita anticline was a rising, positive structural element during Atoka deposition. A thickened Atoka sequence is found to the north of this feature, and overlaps and thins across it. This was unrecognized in previous fusulinid studies which infer that Fusulinella occurs 100 ft above Profusulinella when the actual stratigraphic separation is over 1,000 ft. 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 Atokan time.

The Atoka sandstones, with updip pinchout and overlapping mudstones, can be stratigraphic traps for small hydrocarbon accumulations in the subsurface on the flanks of the Clarita anticline.