Magnetic prospecting at a prehistoric and historic settlement in Maine

Magnetic surveys at a prehistoric and historic site in Maine were performed in order to improve understanding of cultural features identified from excavations that detailed cultural characteristics at discrete locations, but failed to define the geometry and extent of subsurface features. The objective of the magnetic work was to non-invasively define this spatial distribution of features. Such information is required to nominate both sites to the US National Register of Historic Places. Environmental and cultural factors in Maine favour the application of the magnetic method in archaeological prospecting. At the Spiller Farm palaeoamerican site, excavations had revealed a hearth and over 130 fragments of stone tools. The objective of the magnetic survey was to define additional hearths and cultural material within the vicinity. Measurements were made on a 45 by 25 m grid at 1 m intervals. Signal processing improved definition of a +50 nT anomaly that, upon partial excavation, was found to be associated with a sizeable burnt feature. Laminations in the excavated feature, combined with an increase in palaeo-artefact counts around it, indicate that the feature is a palaeo-hearth, rather than a natural burnt feature. At the Fort Hill historic site, previous excavations revealed a hearth, stone debris related to the fort foundations and numerous historic artefacts but did not resolve the fort geometry. Magnetic measurements were performed on a 55 by 45 m grid at 1 m intervals. Linear anomalies (+20 nT) were interpreted primarily as the response to residual metal in the fort foundations. The geometry of the fort and the meeting house, known to exist from historic accounts, were directly inferred from the survey. The hearth location and artefact distribution correlate well with the magnetic data. The dimensions of the fort (41 by 19 m) were found to be considerably larger than that expected from historic references. Copyright © 2000 John Wiley & Sons, Ltd.