INVESTIGATION OF A POSSIBLE INDIAN MOUND USING LIDAR AND GROUND-PENETRATING RADAR (GPR)

We evaluate the archaeological and geological content of a possible Indian mound located in north Florida using contour mapping of LiDAR data as well as 2D and 3D mapping of the subsurface with ground-penetrating radar (GPR). We believe this mound to have been built during the Mississippian period (800-1600 CE) when the practice of mound building was widespread. Contour mapping of LiDAR data indicates an elevation of over 65 feet (20 meters) above the surrounding terrain and a surface area of approximately 160 acres (65 ha). If the feature is cultural then it is the tallest known Indian mound in Florida by over 15 feet. In order to identify geophysical anomalies which may indicate both natural and cultural features, we used a MÅLA 500 MHz GPR antenna to survey a grid of 75 x 100 m covering most of the mound surface. Profiles were initially processed in 2D using RadExplorer, correcting the “time zero,” removing DC signal noise, and correcting amplitude for signal loss with depth. Time slices of 4 ns each were also mapped from the raw data using GPR Process. The GPR results show disturbance to the mound both by tree roots and by a significant ramp or trench for the road which runs up to the top from the northeast. At least one metal object near the surface can also be identified from “ringing” in the radar signal return. Several rectangular anomalies near the summit of the mound at approximately 80-160 cm below surface are of particular interest as probable prehistoric features. Additional 2D and 3D analysis of our GPR data as well as fieldwork to ground-truth anomalies should help to confirm that this feature is a prehistoric cultural mound.