TESTING A NEW STRATIGRAPHIC CORRELATIVE TOOL WITH THE NONMARINE LIMESTONES OF THE PENNSYLVANIAN NEAR MACKSBURG, OHIO

The continental Pennsylvanian and Permian rocks of southeastern Ohio display poor lateral continuity because of the lack of diagnostic flora and fauna, rapid lateral facies changes, and paleosols with many erosional incisions. With no prominent marker beds, such as coal and marine limestones, correlation across the area of the mudrocks, sandstones, and nonmarine limestones, interpreted originally as cyclothems, is difficult. A geochemical correlative tool is needed to precisely identify similar beds across the region. Strontium isotopic ratios (⁸⁷Sr/⁸⁶Sr) from the nonmarine limestone units have been used to reconstruct the tectonic history of these Late Paleozoic rocks, though sampling to date has been restricted to one sample per unit to observe changes over time. Because Sr isotopic ratios are seemingly unique to each limestone unit, it is probable that they reflect the signal of the drainage area rocks at the time of deposition and can be used as a correlative tool. More precise stratigraphic correlation will facilitate more detailed paleoenvironmental reconstructions across the region.

To test the applicability of Sr isotopes as a correlative tool, ten limestone samples were collected across the bottom of a limestone layer in the Monongahela Group (Pennsylvanian) exposed near Macksburg, OH in northern Washington County to see if the Sr isotopic ratios were similar across this nonmarine unit. Sr isotopic ratios ranged from 0.710414 to 0.710441. The non-parametric Kolmogorov-Smirov statistical test confirmed that these data reflect one population. The next field test is to compare these data with that from a probable correlated unit in Athens County to the west. Detailed petrographic work on the nonmarine limestones shows that they are palustrine carbonates developed on a siliciclastic fluvial floodplain of a probable anastomosing river system sourced from the east.