Date of this Version
Depositional patterns and regional stratigraphic relationships in the carbonate-dominated Pennsylvanian and Permian deposits in western Nebraska are not well established due to poor surface exposure. Examination of petroleum drillcores and wireline logs, along with thin sections and biostratigraphic analysis allow new insight into facies distributions, depositional environment, and regional stratigraphic relationships. Nine shallowing upward cycles are identified that can be correlated across the southern Nebraska Panhandle within the Pennsylvanian (Virgilian)-Permian (Wolfcampian) stratigraphy (Admire, Council Grove, and Chase Groups). These cycles are composed of facies representing deposition from open marine through nonmarine environments. Results show that depositional settings in western Nebraska were shallower and more restricted than in other nearby areas of the Midcontinent and that regional climatic conditions became more arid through time, from the Pennsylvanian into the Permian. Increasing our understanding of these subsurface relationships will be useful in two primary regards. First, it will aid petroleum exploration efforts in this region by providing a better understanding of depositional patterns and facies variability, and second, it will contribute to our knowledge about regional variations in climate and their increasing aridity through time.