--> Abstract: Sequence Stratigraphy And Depositional Dynamics, Atoka Formation (Middle Pennsylvanian), Southern Ozarks, Northeastern Oklahoma And Northwestern Arkansas, by E. J. Valek, W. L. Manger, T. A. (Mac) Mcgilvery, and D. L. Pearson; #90928 (1999).

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VALEK, EDWARD J.1, WALTER L. MANGER1, T. A. (MAC) McGILVERY2, and DANIEL L. PEARSON2
1University of Arkansas, Fayetteville, AR
2Phillips Petroleum Corporation, Bartlesville, OK

Abstract: Sequence Stratigraphy and Depositional Dynamics, Atoka Formation (Middle Pennsylvanian), Southern Ozarks, Northeastern Oklahoma and Northwestern Arkansas

Deposition of the Atoka Formation (Middle Pennsylvanian) in the northern Arkoma Basin and adjacent shelf is characterized by an alternation of sandstones and shales. The sequence represents successive packages of fluvial-deltaic systems that prograded and aggraded across the Arkoma shelf just prior to, and during its flexural down bending into the Arkoma foreland basin. Sand-rich facies are attributed to channel and delta front subenvironments and mud-rich facies represent delta plain interdistributary bay and marine shelf settings. The distinction between the two mud-rich facies is made on the basis of color, palynofacies, and lateral persistence. Composite deltaic systems are constructive and coelesce along strike yielding an apparent sheet-like geometry. High frequency sequences within these complexes are the result of the interplay between sediment supply, autocyclic lobe switching and tectonic subsidence. Genetic stratigraphic sequences are bounded by maximum flooding surfaces defined by black, prodeltaic shales in outcrop and high gamma-ray log signatures in the subsurface. Correlation of outcrops along the northern Arkoma Basin linked to log motif in wells from producing gas fields to the south provides an outstanding surface-subsurface analog for application of high frequency sequence stratigraphy and recognition of productive, sand-rich depositional facies.

Reservoir quality is preserved in sandstone intervals that possessed high initial porosities related to the energy of their environmental setting. Traps are either stratigraphic or anticlines resulting from normal faulting. The Atoka Formation is internally sourced from shales that produce mostly dry methane.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas