The post-Hunton unconformity in southern Oklahoma is evidenced by the age of the rocks encountered at the base of the Woodford shale. A pre-Woodford distribution study illustrates the magnitude of pre-Mississippian folding, and suggests a tectonic framework for delineating pre-Woodford structural trends. An isopachous study of the Hunton suggests that the first pronounced structure building in southern Oklahoma occurred during middle Hunton time, at the close of the Silurian Period. The Hunton exhibits radical variations in thickness as a result of truncation at the basal Woodford unconformity and also the unconformities and facies changes within the Hunton group. Woodford rests unconformably on rocks ranging in age from Arbuckle, in the Hollis basin in southwest Oklahoma to upper Hunton, in south-central Oklahoma. A unique carbonate sequence attaining a maximum thickness of 115 feet in the subsurface occurs at the base of the Woodford shale, and rests unconformably on beds as old as Viola along the Mannsville-Aylesworth anticlinal trend in south-central Oklahoma. This carbonate occurrence, its lithologic description, and its possible relationship with the outcrop are briefly discussed.