ABSTRACT

The Middle Pennsylvanian (Desmoinesian) "Cherokee" Group consists of cyclothemic sequences which represent transgressive-regressive couplets. Regressions, which interrupted an overall transgression of the Cherokee sea, are marked by the presence of five lenticular sandstone units in the study area. In descending order, these sandstones are known as the Prue, Upper Skinner, Lower Skinner, Red Fork, and Bartlesville. The geometry of each of the "Cherokee" sandstones was determined from sub-surface data which served as the basis for estimation of depositional environments and interpretation of sandstone trends.

Each of the sandstones in the area is thought to be representative of deltaic environments, and the sandstone bodies are classified as major and minor distributary channel deposits and delta-fringe deposits. The latter includes a variety of sandstone bodies such as distributary-mouth bars and offshore bars. The Bartlesville and Prue sandstones have dominant northeasterly trends, whereas, trends for the Red Fork, Lower Skinner, and Upper Skinner are north-south. Stacking of genetic units in some of these sandstones resulted in a complicated geometry associated with multistoried and multilateral units.

Local structural trends are a reflection of basement-fault configuration at depth and possibly differential compaction, although the latter has not been clearly demonstrated. Rocks of the "Cherokee" Group are the oldest Pennsylvanian units in the area and unconformably overlie a Mississippian surface which was extensively eroded during Late Mississippian and Early Pennsylvanian time. Paleotopography influenced the distribution of lower "Cherokee" sediments, particularly the trend of the Bartlesville Sandstone in the eastern part of the area. Paleostructural control, characterized by differential compaction, structural movement, or a combination of both influenced the distribution of upper "Cherokee" sediments.

Log maps are thought to improve the accuracy of determining sandstone trends and estimating sandstone edges. They represent a more useful exploration tool for delineating subtle sandstone trends than conventional isopach maps.