DELINEATING HOLOCENE FLOODPLAIN TERRACE SEQUENCES ON UPATOI CREEK, FORT BENNING, GA

Fluvial terrace sequences represent potential archives of Quaternary palaeoclimatic fluctuations and fluvial system behavior. Upatoi Creek is a major tributary of the Chattahoochee River in west central Georgia south of the Fall Line and drains a major portion of Fort Benning Military Reservation. Watersheds in the region have experienced legacy sedimentation from historic land clearing and agriculture; landuse and maneuver activities associated with the relocation of the Armor School to Fort Benning are expected to increase catchment disturbance and sediment delivery to streams in the installation. The Upatoi and its tributaries have incised into their former floodplains, forming the T1 terrace about 3 to 4 m above stream level, leaving extensive abandoned terraces 3-4 m above the current floodplain with multiple meander scars and other features. Paleoenvironmental investigation of an abandoned meander scar with basal dates of 9,940 ±220 yr and 10,310±220 yr record a drier, diverse early Holocene forest with Quercus, Pinus and abundant non-arboreal pollen. Increases in Nyssa indicate wetter conditions by the mid-Holocene. Forests continue to be dominated by tupelo until historic times, when their decline indicates a lowering of the water table due to incision of Upatoi Creek. General patterns are consistent with the regional synthesis reported by Leigh (2008). Currently, a high resolution DEM derived from LIDAR data is being used to map the floodplains of Upatoi Creek and its larger tributaries. Objectives include identifying and mapping floodplain features that may include multiple terraces and features for further paleoenvironmental research.