PLEISTOCENE LANDFORMS ON OSSABAW ISLAND: EVIDENCE FROM SOILS, PALEOSOLS, AND DIGITAL CARTOGRAPHY

Ossabaw Island is a relatively pristine barrier island currently located just south of the mouth of the Ogeechee River on the Georgia coast. The modern island contains at least one remnant island from the Pleistocene onto which shoreface sands have accreted. While efforts to obtain absolute age constraints have so far proven unsuccessful, the soils mapped on the island do delineate remnants of the Pleistocene island. Spodosols which contain deeply buried organic matter accumulations are mapped entirely within areas which define a ridge toward the landward side of the island. Recent coring at two locations along this ridge identified buried A horizon sediments at depths ranging from 1.5 - 2.5 meters below the present land surface. Preliminary laboratory results identify the paleosol based upon soil particle size, percent organic matter, and soil pH. Reconstructions of the appearance of the island when submerged are consistent with formation of the paleosol during the last interglacial (MIS 5e) highstand (~135 ka). However, alternative periods of formation during MIS 5a (~87–77 ka), MIS 3, or even the last glacial maximum may be more consistent with the soil morphology and sedimentology which success a backshore, dune, or upland pine forest environment.