LITHOLOGY AND PALEONTOLOGY OF THE SANDERSVILLE LIMESTONE MEMBER OF THE TOBACCO ROAD SANDSTONE ON THE COASTAL PLAIN, GEORGIA

The Sandersville Limestone member of the Tobacco Road Sandstone of Georgia has long been recongnized solely from its limited exposures near the type locality near Sandersville, GA. Recent research on the Sanderville member has extended the geographic extent along a northeast-soutwest transect of the upper Eocene outcrop belt within the Georgia Coastal Plain. The Sandersville member has a diverse marine fossil assemblage dominated by byrozoa, mollusks, and echinoids. Other fauna present are foraminifera, ostracods, ophiuroids, fish, marine reptiles, and mammals. Based on the fossil assemblages, the Sandersville member is middle Jacksonian in age. The depositional environment is nearshore to open marine. Smectite, trace amounts of kaolinite, and illite are the clay minerals found in the Sandersville member. The amount of insoluble residue increases southwest of type locality and quartz is the dominant mineral present in the insoluble residue. The Sandersville member underwent a diverse diagenetic history ranging from carbonate dissolution to pervasive silicification. It is highly silicified northeast of the type locality and silicification occurred during early diagenesis by percolation of silica rich waters locally derived from the overlying Tobacco Road Sandstone. A tentative Eocene shoreline for middle Jacksonian time has been determined for the Sandersville member.