HYDROCHEMISTRY AND SEDIMENTOLOGY OF THE LITTLE TALLAPOOSA RIVER FLOODPLAIN, PIEDMONT PHYSIOGRAPHIC PROVINCE, GEORGIA, USA

An ongoing study on the University of West Georgia campus examines hydrogeology and sedimentology of a riparian wetland located on the floodplain of the Little Tallapoosa River in the Piedmont Physiographic Province, Carroll County, Georgia. The site is underlain by three main types of regolith: 1) organic-rich, predominantly fine-grained, Holocene floodplain alluvium, 2) coarser-grained, pedogenically altered (Pleistocene?) terrace alluvium, and 3) saprolite; sampling wells have been installed in all three media. Alluvium ranges from zero to at least 4.8 m in thickness. Local variations in major-ion water chemistry appear to be strongly controlled by regolith type, particularly organic-rich Holocene alluvium, which significantly affects redox-sensitive species such as Fe²⁺, NO₃^- and Mn²⁺. A 4.1m sediment core in Holocene alluvium was collected in 2011 using the Vibracore method. The core reveals silt- and clay-rich fluvial sediments, minor peat, and a buried soil horizon at a depth of 2.6 m. Basal core sediments show a conventional C-14 age of 750 +/-30 BP; a second sample above the buried soil horizon gives a conventional C-14 age of 10 +/-30 BP. We also measured sediment concentrations of Cd, Cu, Ni, Pb, and Zn at approximate 0.15 m intervals using an aqua regia digestion and ICP-AES analysis. Sample concentrations are significantly below modern background levels at depths below the buried soil horizon and at or above modern background above the soil horizon. We tentatively interpret the buried soil to represent the pre-settlement land surface in this area.