Foraminifera in the Atoka Formation were studied to demonstrate their usefulness in stratigraphic zonation and to attempt interpretation of the environment of deposition and paleoecology of the Atoka beds in which Foraminifera occur.

Five stratigraphic sections of the Atoka Formation, the greatest 5,600 feet thick, were described and shale samples were collected for microfaunal analysis. No Foraminifera were found in Atoka sandstones.

The Atoka Formation in the central Ouachitas is typical black shale flysch. It consists of a thick series of alternating beds of fine-grained, graded sandstones and black shales. The lower half of the formation is sandstone facies featured by thick massive sandstones. The upper half of the formation is shale facies featured by thin turbidite sandstones.

The Atoka microfauna is composed of a few conodont specimens, abundant monaxonid, and hexactinellid seliceous sponge spicules, Radiolaria, and a rich assemblage of siliceous arenaceous Foraminifera consisting of 20 genera and 42 species. The foraminiferal assemblage is a typical flysch assemblage dominated by species of four genera: Thuramminoides, Ammodiscus, Hyperammina, and a new species of Agathammina.

Thurammina diforamens, robust specimens of Hyperammina bulbosa and Reophax fittsi, small specimens of Hyperammina casteri, and Hyperammina expansa, Ammodiscus constrictus, Glomospira cf. "G. pusilla," Textularia

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"eximia Eichwald," and Paleotextularia grahamensis are diagnostic of lowermost Atoka strata.

Foraminifera were not found in the Atoka sandstone facies where the sandstone: shale ratio exceeds 0.50.

Small specimens of Hyperammina bulbosa and of Glomospira articulosa, and robust specimens of Hyperammina casteri are diagnostic of the lower part of the shale facies. Spiroplectammina parva, Trochammina rudis, Mooreinella biserialis, and species of Ammobaculities are diagnostic of the lower part of the shale facies.

Only the lower 1,000 to 2,000 feet of the Atoka Formation in the central Ouachitas is Morrowan; all of the overlying Atoka strata are Atokan.

All of the Atoka strata in the Kiamichi Range and the sandstone facies in the Winding Stair Range were deposited in an outer neritic to upper bathyal basin. The allocthonous sandstones were deposited by a combination of overloaded normal marine currents and turbidity currents. The upper shale facies in and north of the Winding Stair Range was deposited in a deep bathyal reducing basin. The allocthonous sandstones were deposited by turbidity currents.

PHILIP H. STARK

Philip H. Stark is an Exploration Geologist for Mobil Oil Company in Wichita, Kansas. After attending the State University of Iowa, he continued studies at Oklahoma University, receiving a B.S. degree in 1958, and completed graduate work in geology at the University of Wisconsin, receiving an M.S. degree in 1961 and a Ph.D. in January, 1963. His experience in the petroleum industry includes stratigraphic studies in the San Juan and Permian Basins, in north central Texas, southern Oklahoma and the Hugoton Embayment in Kansas. Mr. Stark is a member of Sigma Gamma Epsilon, Sigma Xi, S.E.P.M., G.S.A. and A.A.P.G.

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