AN ALLUVIAL SOIL CHRONOSEQUENCE ALONG SNAKE CREEK IN THE WESTERN PIEDMONT OF GEORGIA, USA

The Snake Creek valley contains at least five different alluvial units, historical to Pleistocene or earlier in age, that document a sequence of soil development in the humid subtropical climate of the west Georgia Piedmont. Snake Creek, a 5th order tributary to the Chattahoochee River with a 90 km2 basin area, was examined to provide geomorphic context to archaeological data recovery excavations prior to impoundment of a reservoir. The modern flood plain (TO), deposited since European settlement of the region as dated by historic-period artifacts, has weak soil development, a single grained structure, no clay films, and abundant charcoal. The pre-historic flood plain (T 0.1) is covered by up to ~1 m of historical sediment, has a cambic horizon with weak prismatic structure, and abundant charcoal. Radiocarbon dates and artifacts indicate that terraces T1 and T2 were occupied by humans during the Early and Middle Woodland periods, 2600-2100 years BP, and possibly as early as the Early Archaic period, 9950-7700 years BP, and therefore predate this time. The T1 terrace soils have argillic horizons with moderate prismatic structure and faint clay films. The T2 terrace soils have argillic horizons with moderate to strong prismatic structure and distinct clay films. The T3 terrace has a thicker argillic horizon with moderate prismatic and angular blocky structure and distinct clay films. The oldest observed terrace (T4) has a >100 cm thick argillic horizon with moderate prismatic structure and distinct clay films. Soil colors become increasingly red with age, reddest colors ranging from 7.5 YR 4/6 for the floodplain to 10 YR 4/6 for terrace T4. Soil thin sections are being examined to quantify growth of clay films for the different aged units. These observations help to establish relative age indicators for alluvial soils in the southeastern Piedmont.