CORRELATION OF UPPER THREE RUNS AQUIFER TO THE EOCENE SANDERSVILLE LIMESTONE, COASTAL PLAIN GEORGIA
The Upper Three Runs Aquifer is a partially lithified wackestone containing calcite, fine-grained quartz, and abraded pelecypods, gastropods, and bryozoa. Clay mineralogy determined by X-ray diffraction shows smectite, heulandite and opal-CT. Bryozoa species Ochetosella Jacksonica, of middle Jacksonian age in central Georgia, was identified by scanning electron microscopy (SEM). Heulandite is an authigenic phase based on SEM images.
Based on our results, the Upper Three Runs aquifer is age correlative to both the Middle Jacksonian Sandersville Limestone and to the Ocmulgee Formation in the western Georgia Coastal Plain. The low fossil abundance and diversity, fine-grained clastics, and the presence of smectite indicate the Upper Three Runs was deposited in a deeper marine setting relative to the shallow marine depositional environment of the fossiliferous Sandersville member and Ocmulgee Formation.