PRELIMINARY FACIES ANALYSIS OF THE TWIGGS CLAY FORMATION AT THE SARA DUKES MINE, SANDERSVILLE, GEORGIA

The Twiggs Clay is a smectitic clay unit as much as 100 feet thick throughout the Coastal Plain of central and eastern Georgia. With the underlying Clinchfield Sand, these two units are the updip clastic equivalents of the Ocala Limestone in southern Georgia and peninsular Florida.

Twiggs Clay and Clinchfield Sand are well exposed at Thiele Kaolin Company's Sara Duke mine about 7 miles east-southeast of Sandersville. A Late Eocene (Jacksonian) age is indicated for the Twiggs Clay there, based on the presence of the benthic foraminifera Cibicides, Cibicidina, Elphidium, and Valvulineria. Cibicindina has not been previously recognized in the Twiggs Clay in Georgia. Ostrocodes, bryozoans, gastropods, pelecypods, sponges, barnacles, and marine vertebrate teeth, were also found in basal Twiggs Clay at the Sara Dukes Mine. The observed benthic foraminifers and other calcareous fossil material, and the presence of high percentages of siliciclastics ranging in particle size from sand to unoxidized smectite clay, indicate a low energy, reducing marginal marine environment typical of deposition between the Late Eocene shoreline and an offshorebarrier bar.