CARBONATE EOLIANITES IN THE MISSISSIPPIAN MAXVILLE LIMESTONE OF SOUTHEAST OHIO

A number of Paleozoic and Mesozoic limestones have been reinterpreted as carbonate eolianites based on outcrop scale and petrographic criteria. It has been shown that structures traditionally associated with subtidal marine sands or eolian dunes can be found in both and may not be diagnostic of either. At present, reverse grading associated with wind ripples seems to be the most diagnostic criterion for eolianites. Additional petrographic criteria include but are not limited to fine (thin section scale) lamination, broken and abraded ooids and skeletal grains, a lack of large skeletal grains, and tight packing of grains.

Four cores of the Late Mississippian Maxville Limestone from southeast Ohio preserve a basal sandy grainstone that comprises eolian dune, subtidal shoal, and possibly beach facies. Sandy grainstones are overlain by muddy lagoonal and tidal flat sediments. The sandy grainstones of the lower Maxville have been correlated to the Loyalhanna Limestone of northern West Virginia and southwest Pennsylvania portions of which have also been shown to have an eolian origin.

Total thickness of the Maxville Limestone ranges from 15 to 32 meters in the cores. Sandy grainstones present at the base of the Maxville vary from 6 to 9.5 meters in thickness. In one core, the lower 2 meters of the sandy grainstone is dolomitized and highly porous. Exposure surfaces are present throughout the Maxville Limestone and are commonly found at the top of the grainstone facies.

The sandy grainstones are composed of well sorted, fine to medium sand size quartz and carbonate grains including skeletal grains, peloids, and ooids. Some portions are cross-bedded while others are massive. Cross beds are distinguished by variations in grain size and grain composition. Fine lamination and inverse grading are commonly present. Cross-bedded grainstones also contain broken and abraded skeletal grains and ooids and are tightly packed. These grainstones are interpreted as carbonate eolianites. Grainstones with low angle laminations are also recognized. These units include thin beds of larger shells and clasts and may be beach deposits associated with the dunes. Massive grainstones are sometime mottled and burrowed and may represent nearshore subtidal sands or vegetated parts of the dune where cross bedding has been destroyed.