USING INTEGRATED GEOPHYSICAL METHODS TO FIND THE SITE OF AN 18th CENTURY TAVERN IN YORK, MAINE

At the request of The Museums of Old York, an integrated EM induction, ground penetrating radar (GPR) and electrical resistivity survey was conducted on a site in York, Maine. This site is reputed to be the location of a 17^th century garrison house, later converted during the 18^th century into a tavern named the Green Dragon. The data acquisition grid for the site was 36 x 36 meters. Data lines were at meter intervals for the EM and GPR. The EM data (InPhase, Quadature, and Conductivity) were collected using 15 KHz, 10 KHz, and 5 KHz frequencies. The GPR data were collected using a 400 MHz antenna with a 50 ns window. The electrical resistivity data were collected along three lines within the grid using a Wenner array with a 1.6 α meter spacing. The EM and resistivity surveys were used to provide a reconnaissance of the site’s subsurface to focus in on potential areas of interest. The EM data was post-processed using MagMap2000_© and Surfer10_© using specifically the conductivity data. The resistivity surveys were post-processed using RES2DINV_© software. Once these areas were determined, they were then compared to the GPR data to provide evidence that an anomaly was present. The GPR data was post-processed using Radian_© 6 software. By using these techniques it was determined that anomalies potentially representing the foundation of the Green Dragon were found in the field area. The suspected anomaly is roughly 10m x 5m in size, which is typical of the dimensions of garrison houses built during the 17^th century. However, anomalies in other areas of the site suggest the presence of additional structures. One of these anomalies was collected by a resistivity survey line, which showed the anomalous feature 10 meters north of the suspected foundation. This anomaly is also present in the EM and GPR data and may represent the foundation of a barn.