3D Seismic Interpretation of Paleokarst Sinkholes, Boone Limestone, Lower Mississippian: Subsurface Eastern Arkoma Basin, Conway County, Arkansas

Unconventional natural gas discoveries in the Fayetteville Shale of the eastern Arkoma Basin have led to improved understanding of subsurface geology in central Arkansas. This study interprets 3D seismic data for evidence of paleokarst within the Mississippian formations in a portion of the subsurface of Conway County, Arkansas. Quantitative data interpretation suggests that sinkholes developed during the Mississippian portion of the eastern Arkoma Basin record.;In a nine square mile area, 3D seismic mapping of Mississippian formations show 14 closed depressions interpreted as karst sinkholes. Time and depth structure maps were created and utilized to estimate the timing of dissolution and infill of the sinkholes. Measuring the size and morphology for each sinkhole, histograms were made to summarize sinkhole characteristics. Sinkhole areas in the Boone Limestone correspond to areas of low acoustic impedance, likely indicating enhanced porosity due to fractures and dissolution.;Scale of the observed sinkholes suggests that they are consistent with modern solution sinkholes. Sinkholes in the study area occupied 10.7% of the entire Boone Limestone surface. Structure maps suggest that dissolution and collapse of the Boone continued throughout the marine transgression and deposition of both the Moorefield Shale and Hindsville Limestone in the Meramecian and early Chesterian. Final filling was accomplished during the deposition of the Fayetteville Shale in the late Chesterian. Regionally, sinkholes developed in early Ordovician carbonates have been filled with late Pennsylvanian sediments.