Middle Paleozoic rocks of Oklahoma comprise the Middle Ordovician Simpson Group, the Viola Limestone, the Sylvan Formation, and the Siluro-Devonian Hunton Group. This essentially conformable succession of strata represents a sequence, or body of rock bounded by time-transgressive interregional, unconformities. Units overlying this sequence, the Mannsville Dolomite (new name), Woodford Shale and Misener sand, show progressive onlap from southwest to northeast and represent transgression of the succeeding depositional episode. A study set in the framework of these natural rock units, instead of time-stratigraphic units system, series, and stage, leads to a more logical interpretation of part of the Paleozoic history of Oklahoma; projection of the sequences onto a time-lengt cross section (horizontal axis, distance, vertical axis, time) has afforded a visual representation of this history. Subsurface investigation of the physical relationships of formations within the Hunton Group has shown that the unit represents almost continuous sedimentation from Medial Silurian through Early Devonian.