Abstract: Geologic Provinces of Oklahoma
Robert A. Northcutt, Jock A. Campbell
The geologic provinces of Oklahoma are mainly the product of tectonics and attendant sedimentation of Pennsylvanian age. Most boundaries are structural; thus, the provinces map is a generalized tectonic map. Permian and post-Palezoic strata tend to mask those structures, but most of those strata have been removed by erosion, except in the Anadarko Basin and the Wichita Uplift provinces. The location of most of Oklahoma's oil and gas resources are either influenced by, or are the direct result of Pennsylvanian tectonics and sedimentation patterns. Therefore, the present study also defines provinces in the subsurface on the basis of geological criteria. The authors have attempted to use the originally published names for the recognized provinces. However, we have also used he most geologically correct names, i.e., Nemaha Uplift, Nemaha Fault Zone, and Central Oklahoma Fault, in lieu of Nemaha "Ridge."
Oklahoma is separated into five major uplifts and five major basins. Most of these have subprovinces, which sum to 20 additional identified geologic units. The Gulf Coastal Plain is not included in this study because it is a veneer of Cretaceous cover that masks significant structures. Faults are the most common boundary element. Although their precise age commonly is known only approximately, their geographic location is less controversial, except in detail. Stratigraphic/structural boundaries are based on less precise geological information. Such boundaries interpreted at the surface are influenced by both geology and geomorphology, and are therefore strongly influenced by the present level of erosion. The major example of a surface stratigraphic/structural boundary is the southwest rn limit of the Ozark Uplift in eastern Oklahoma. Stratigraphic/structural boundaries in the subsurface are commonly based on structural or isopachous contours from well or geophysical data, or on a structural trend, as well as the experience of the authors. Basement structure is preferred. An example is the boundary that separates the Marietta Basin from adjacent geologic elements.
Important subsurface boundaries in the Anadarko and Arkoma Basins have been neglected in previous studies: The Anadarko Basin/Shelf boundary is placed near the 700-ft isochore of the Atokan and Desmoinesian Series (Rascoe, 1962), at which there is a marked rate of change of thickening southward into the basin. The northern limit of the Arkoma Basin seems to merge imperceptibly into the southern part of the Cherokee Platform, and has been variously drawn by a number of authors. For the purpose of this study the boundary is modified from the "hinge line" of the Atokan Series (Weirich, 1953). This boundary approximates the striking rate of change of thickness of Atokan strata southward into the Arkoma Basin.
AAPG Search and Discovery Article #90957©1995 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma