Stratigraphy and Economic Potential of Cambrian and Lower Ordovician Rocks in Ohio

Abstract: Fine-grained to conglomeratic basal Mt. Simon Sandstone (0–350 ft) is overlain in western Ohio by fine-grained glauconitic Eau Claire Sandstone (200–600 ft) and in eastern Ohio by Rome dolomite and poorly sorted sandstone (190–750 ft). The Rome is overlain by the Conasauga Formation (40–400 ft), consisting of siltstone, sandstone, limestone, dolomite, and southward-thickening prodelta shale. Eau Claire and Conasauga are overlain by a deltaic sandstone (0–170 ft) derived from the north; in northeastern Ohio the equivalent rocks are dolomite and discontinuous sandstone. The Knox Dolomite (0–1,200 ft) overlies these beds and in eastern Ohio includes the Rose Run sandstone (100–120 ft). Both Rose Run and deltaic sandstone subcrop below the Knox unconformity as potential traps. Only one show (gas) has been recorded from the Mt. Simon. Younger sandstones (Rome, Conasauga, deltaic, Rose Run, and unnamed sandstone in the Knox) are potential reservoirs where they have structure or form stratigraphic traps (porosity pinchouts, facies boundaries, erosional highs below the Knox unconformity). Gas and oil have been produced from the Knox from both structural and stratigraphic traps. Prime exploration areas are north-central Ohio, where sediments were deposited close to the shoreline, and eastern Ohio, currently active, where secondary porosity below the Knox unconformity has created gas reservoirs.