North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: Fort Stewart;
Reference: Butler, Dwain K., Jose Llopis and Frederick L. Briuer (1993). Geophysical and Archaeological Investigations for Location of a Historic Cemetery, Fort Stewart, Georgia; prepared for U.S. Army Engineer District, Savannah.
A geophysical and arcaheological investigation was conducted at Fort Sttewart, Georgia, in order to locate a historic cemetery (the Durrence Cemetery). After examination of historical documents, maps, and aerial photos, an area of 45 x 80 ft was surveyed where the location of the site was likely. The cemetery was used during the approximate period 1808-1880 and reportedly contains 10-12 graves. Fort Stewart personnel desired to non-invasively confirm the existence of graves in the identified area. The area would then presumably be fenced.
Three geophysical methods are generally used in programs for grave location: ground penetrating radar (GPR), electrical and ectectromagnetic (EM) surveys, and magnetic surveys. WES (Waterways Experiment Station) personnel conducted these types of surveys over an area 100 ft by 120 ft approximately centered on the smaller area mareked by District personnel. Total magnetic field measurements were acquired at 10ft intervals over the complete grid with a proton precession magnetometer. Two electromagnetec survey instruments were applied at the site, the EM-31 and EM-38. While the EM-31 (taken at 10ft intervals) has a depth of investigation of approximately 20ft , the EM-38 (taken at 5ft intervals) has a depth of investigation of approximately 5ft. Magnetic anomalies can be correlated with electromagnetic anomalies to help discriminate between subsurface objects/features which are metallic and electrically conductive or are non-metallic and electrically conductive. GPR surveys were conducted along 13 east-west lines and 2 north-south lines.
Most of the isolated EM anomalies are attributed to small, surface metallic objects. One magnetic and one EM anomaly cannot be explained by known features. These are also shown in the GPR image. In terms of confidence ranking criteria, three factors should be considered: (1) spatial correlation of anomalies from differenct geophysical methods; (2) nature of the anomalies consistenct with that expected for a grave (burial); (3) GPR anomalies identifed by both independendt interpresters; (4) location of the anomaies within or immediately adjacent to the cemetery area marked by District personnel.
Results of the geophysical surveys indicate the existence of subsurface anomalous features. There are 10 geohysical anomalies within or immediately adjacent to the marked cemetery location that satisfy the four confidence ranking criteria. Othe geophysical anomalies existed within the surey are which do not suatisfy all the four criteria. The convergence of diverse types of evidence supports a recommendation to recognize the site as the "Durrence Cemetery."