Biostratigraphically constrained ages of Mississippian mixed carbonate-siliciclastic sequences, STACK play, Anadarko basin, Oklahoma

Abstract

The ages of Mississippian stratigraphic intervals within the STACK play of the Anadarko basin remain poorly understood due to the lack of biostratigraphic constraints. Godwin (2018) refined outcrop stratigraphy of Meramecian and Chesterian strata in northeastern Oklahoma and described siltstones and carbonates similar to those observed in STACK rocks. The four principal conodont biozones in the Meramecian through middle Chesterian outcrop sections were recognized in conodonts recovered from the Pan American, Barnes D-2 core from Major County. These results revealed that given the recovery of distinct taxa, these four key biozones are recognizable in a subsurface section and provide a mechanism for constraining the ages of the Mississippian intervals in the study area.

A sequence stratigraphic framework based on depositional facies and vertical stacking patterns within the Barnes core was correlated with the principal biozones and electrofacies from wireline logs. The contact between the Meramecian and Chesterian ages was identified honoring biostratigraphic constraints. The Osagean and Meramecian boundary however, could not be resolved due to limited conodont recovery. Osagean rocks may still be present in the Barnes D-2 core, in the approximately 200 feet of Mississippian carbonate section below the first identified biozone. Using stratigraphic surfaces including radiogenic intervals on the gamma-ray curve, wireline logs were correlated to identify clinoform geometry. Thirty (30) selected wireline logs were used to construct a cross section that illustrates the Mississippian stratigraphic architecture subparallel to paleodip. This cross section begins in Major County with the Pan American, Barnes D-2 in Section 23, T.22N., R.16W., and terminates with the Pan American, Effie B. York well in Section 13, T.18N., R.09W., northwestern Kingfisher County. This correlation shows that most of the Mississippian section in the Starr-Lacey field area, western Kingfisher County and eastern Blaine County, is early Chesterian and Meramecian.