ABSTRACT Multiple orders of depositional cyclicity in the Mayes Group of northeastern Oklahoma are delineated by refined depositional facies associations and stratigraphic surfaces. Facies associations include deep subtidal facies, shallow subtidal facies (including distal and proximal subfacies), carbonate shoal facies, and shoal crest facies. The Mayes Group records a primary transgressive–regressive depositional cycle bounded below by a major unconformity (sub-Mayes unconformity) and above by an important provincial conodont biostratigraphic boundary and widespread flooding surface at the base of the Fayetteville Shale. Within the Mayes Group, two secondary transgressive–regressive depositional cycles are separated by an interpreted unconformity. The lower Mayes cycle comprises the Bayou Manard and Lindsey Bridge members of the Pryor Creek Formation, whereas the Ordnance Plant Member is grouped with the Hindsville Formation in the upper Mayes cycle. Present in both the lower and upper Mayes cycles are high-frequency shallowing-upward cycles bounded by flooding surfaces. Evaluating the distribution of facies and stratigraphic surfaces within a framework of multiple orders of depositional cyclicity is essential to interpreting the geologic evolution of the southern mid-continent during the Meramecian and Chesterian, and impacts oil and gas production by improving our understanding of reservoir compartmentalization.

ABSTRACT 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 the Mississippian and Woodford Shale such that, locally, Pennsylvanian shales lie directly on the Ordovician Wilcox sandstone. On the eastern side of the field, greater than 400 ft (120 m) of Mississippian strata are present. Mississippian lithologies include (1) porous chert conglomerate, (2) porous tripolitic chert, (3) massive-to-laminated dense chert, (4) dense chert breccia, (5) bioturbated limestone, (6) limestone breccia, and (7) nodular-to-bedded mudstone (shale). The main reservoir rock, tripolitic chert, primarily formed by in situ karst development of subaerial highs (e.g., sponge bioherms and cherty limestone) followed by silica replacement of calcite and partial to complete dissolution of the remaining calcite to form secondary porosity. Tripolitic chert is most common at the top of the Mississippian, but deeper cycles within the Mississippian are also capped by high-porosity, low-resistivity chert. Detailed 3-D lithology and porosity models that are constrained to core, well-log, and seismic-inversion-derived P-Impedance data illustrate the heterogeneous character of the deposits. In general, wells drilled in areas of thin tripolitic chert reach peak-oil production early, but production declines rapidly because of limited reservoir volume. Areas with greater tripolitic chert thickness require more time to reach peak-oil production but produce at higher rates for longer periods and therefore have higher long-term cumulative production. Cumulative oil production is variable even where tripolitic chert is relatively thick; therefore, factors other than tripolitic chert thickness must impact oil production (e.g., karst, fractures, water saturation).

ABSTRACT The Salem Limestone (Valmeyeran, Mississippian) is a preeminent dimensional limestone quarried in a two-county area of south-central Indiana for nearly 200 years. Advances in quarry technology in the past 30 years produce nearly smooth-sawn quarry walls that show the exquisite depositional details of the Salem carbonate shoal. The Salem shoal is part of a large-scale shoaling sequence that produced a carbonate platform during the middle Mississippian that began at the end of Borden Group (Mississippian) delta deposition and culminated with the deposition of the Ste. Genevieve Limestone (Mississippian). The Salem was deposited as a high-energy, but subtidal shoal above fair-weather wave base. Four environments are recognizable within the shoal: active shoal, open lagoon, intrashoal channel, and intershoal channel. A shoal crest environment may also be present as a fifth environment. A hierarchy of bounding surfaces can be defined using the sawed quarry exposures. First-order surfaces are foreset laminae and appear as inclined or horizontal stratification. Second-order surfaces are the contacts between similar bedforms, and third-order surfaces truncate first- and second-order surfaces, representing breaks in sedimentation. Combined they define mesoforms within the shoal complex. Fourth-order surfaces, similar to third-order surfaces, represent a change from a shoal to lagoonal setting. Evidence of hard-ground development occurs along third-order surfaces, associated with encrusting bryozoan holdfasts, corals, and columnar subtidal stromatolites. Tracing surfaces on the quarry walls is vital to reconstructing the internal architecture of the shoal and the processes that operated within it. We will examine this shoal architecture by visiting quarries and an outcrop, and we will visit a mill where quarried stone blocks are fabricated into panels and shapes for buildings.