PHASE II MULTIPARAMETER GEOPHYSICAL ANALYSIS OF A 17TH CENTURY COLONIAL SITE IN WESTERN MAINE

The ongoing Chadbourne excavation in South Berwick, Maine is uncovering the site of a substantial house, barn and outbuildings occupied from 1650 to 1690 and destroyed in a French and First Nations raid in 1690 and never rebuilt. The structures were generally earthfast with either a sill on grade or a shallow trench in the silty glaciomarine clay of the uppermost Presumpscott Fm. A full spectrum of geophysical techniques were employed to discover additional structures and features and clarify the location of suspected structures. Seismics, magnetics and electrical resistivity provided useful results, however, the best data were generated by ground penetrating radar (GPR). Presumably, this was due to infilling of the foundation holes in the clay with silty, fine to medium sands generating a slight contrast in moisture content. Over 7 linear kilometers of radar data were collected, most of which were on lines spaced 20cm apart using a 400mHz antennae. The data were deconvoluted but not migrated. Analysis of the GPR and resistivity data identified two previously undiscovered structures, the probable trace of a palisaded defensive ditch and the possible location of the well.