USE OF GROUND-PENETRATING RADAR AND ELECTROMAGNETIC INDUCTION PROFILING TO IMAGE A BURIED REVOLUTIONARY WAR TRENCH AT CHIMNEY POINT, ADDISON COUNTY, VERMONT

Geoarchaeology studies can provide information critical to investigations mandated by federal and state laws aimed at documenting and protecting historic resources. This study presents the results of a service-learning project conducted by the field geophysics class at the University of Vermont (UVM) for UVM’s Consulting Archeology Program (CAP), which has worked extensively with the Chimney Point Historic Site in Addison County, Vermont. In particular, the goal of this project was to locate a Revolutionary War era defensive trench. This trench, according to an American map from 1815, spans the length of Chimney Point and was dug by a British battalion. Prior work by CAP included a series of test pits that appeared to intersect the trench locally. This project aimed at building on their preliminary findings by imaging the subsurface. Two non-invasive geophysical imaging techniques collected scans of the area that likely contained the trench: Ground-Penetrating Radar (GPR) and Electromagnetic Induction (EMI). The GPR analysis was successful in identifying a continuous linear structure resembling a trench along the surveyed area, while the EMI analysis did not yield conclusive results. A GPR grid was constructed across the hypothesized area of the trench and produced anomalies, which were interpreted as a continuous linear feature. The position of these anomalies when plotted in x-y coordinates were linearly correlated with an R² value of 0.9638. The calculated orientation of this linear feature is approximately in line with the hypothesized orientation of the trench based on CAP’s test pit studies. Although EMI data did not show any features that are attributed to the trench, the position of a former road appeared to be revealed. The fact that the trench was not visible in the EMI data is likely due to conductivity of the infilled soil being close to that of the surrounding soil. However, the GPR data is sufficient to identify the location and trend of the defensive trench. This confirmation adds an important detail to the ever-expanding understanding of human history at Chimney Point.