Three named major cycles of marine transgression and regression (cyclothems) in the lower Cherokee Group are recognized from the Arkoma Basin margin in east-central Oklahoma across the northern Midcontinent shelf, on the basis of distinctive conodont morphotypes. The lowest of these (McCurtain) is characterized by Idiognathodus cf. praeobliquus and absence of I. obliquus and Idiognathoides. The middle cyclothem (Doneley) is the first major cyclothem to yield I. obliquus. The uppermost (Inola) yielded abundant Idiognathodus, Neognathodus and Idioprioniodus, and sparse Gondolella, and is characterized by large numbers of Idiognathodus podolskensis. All three contain large numbers of I. amplificus. At the base of the succession, the genus Idiognathoides in three cores from northeastern Kansas to south-central Iowa confirms the presence of Atokan strata in the Forest City Basin. The McCurtain cyclothem extends from Oklahoma to the Forest City Basin in northeastern Kansas. The Doneley and Inola cyclothems extend from Oklahoma into Iowa. The Inola Limestone of Oklahoma is equivalent to the Hackberry Branch Limestone of western Missouri. The Bluejacket Coal of Oklahoma, at the base of the Inola cyclothem, is likely equivalent to Bluejacket A Coal of Kansas, Weir B or C coals in Missouri, and a middle Laddsdale coal in Iowa. The Rowe Coal of Oklahoma, Kansas, and Missouri, at the base of the Doneley cyclothem, is likely equivalent to the Cliffland Coal of Iowa. Inconsistent marine lithofacies in all three cyclothems suggest a complex depositional history on irregular surfaces.

An integrated stratigraphic analysis of a ~350 ft drill core from Upton County (Texas) has revealed pervasive variability of several key siliciclastic and carbonate lithofacies in vertical section, where organic-rich siliceous mudrock beds alternate with aluminum-rich mudrocks and calcareous gravity flow deposits. Sediment chemistry, especially major and trace elements derived from x-ray fluorescence, captures this variability with high sensitivity. The high frequency chemostratigraphic variability appears to be cyclic, and it is interpreted to represent the first example of deep-water Late Pennsylvanian cyclothems for the Midland Basin. Positive trace metal (Mo, Cr) correlations to total organic carbon and gamma ray response in siliceous mudrocks, in conjunction with abundant pyrite, indicate bottom-water anoxia and possibly euxinia within the basin. The influence of glacial ice-sheets on the water level of the global ocean, in concert with local oceanographic gradients, regional tectonics, and tropical paleoclimate, constitute the primary controls on lithofacies and chemostratigraphy. The results of this study have implications for understanding the depositional history of the Midland Basin, as well as for identifying horizontal drilling zones for resource development.

Subsurface data derived from ~388 ft of drill core from Martin County (TX) were used to understand the depositional setting of the Wolfcamp-D, a petroleum producing interval in the Midland Basin. Elemental geochemistry collected via x-ray fluorescence revealed a highly variable depositional history marked by the deposition of diverse siliciclastic and carbonate lithofacies. Integration of multiple datasets resulted in the interpretation of nine lithofacies, whose deposition appears cyclical. Correlations between molybdenum and total organic carbon indicate slow recharge of bottom waters and anoxic/euxinicconditions within the basin. The presence of phosphatic nodules coinciding with siliceous black mudrocks suggested high levels of primary productivity driven by upwelling. High-frequency sea level variability, driven by far-field glaciation and regional paleoclimate, were key controls on both the chemostratigraphy and lithofacies. Along-strike variability is seen throughout the basin due to paleobathymetry, proximity and connections to paleochannels, and localized structures. Rhenium-osmium (Re/Os) geochronology was conducted on siliceous mudrocks with high total organic carbon. A depositional age of 300 ± 18 Ma was obtained, partially confirming previous correlations to shelf biostratigraphic data. Scatter in the Re/Os data is likely due to mixing in the basin or non-hydrogenous Os incorporated into the analysis due to the method of preparation.

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