Mississippian limestone and chert reservoirs at Tonkawa field in north-central Oklahoma formed on a regionally extensive carbonate ramp. The deposits commonly form shoaling-upward lithofacies successions that stack into high-frequency transgressive–regressive cycles and form reservoir zones. Localized uplift, subaerial exposure, and associated diagenetic processes have significantly impacted lithology and reservoir-quality distribution. Tonkawa field is on the eastern margin of the Nemaha uplift and exhibits an upthrown western block and a downthrown eastern side, which are offset by as much as 500 ft (150 m) of vertical displacement. Erosion of the western block has removed over 450 ft (135 m) of...