Atop Gallows Hill : magnetic susceptibility in archaeological reconnaissance

Abstract

This thesis synthesizes documentary evidence with two major sets of geophysical data in a comparative study between a potential subsurface archaeological feature, tentatively identified as the possible remains of a colonial palisade, and an experimental palisade trench. In 2013 a geophysical survey was undertaken at the Lunenburg Academy National Historic Site, Lunenburg, Nova Scotia. This survey revealed several anomalies, including one that may indicate the 18th century palisade line. In an effort to better understand this feature an interdisciplinary methodology was employed. The background study included a review of historic material on the construction and life span of British era palisades. It was enlightened with environmental and remote sensing data to identify the archaeological potential of Gallows Hill and to provide a framework for the interpretation of geophysical responses from the experimental research component. The objectives of the experimental research were to generate a susceptibility response for an earth filled trench of known dimensions, comparable to British North American palisades, and contribute to a literature on the accuracy of the EM38B inphase component as a non-invasive remote sensing technology, for detecting subtle features. The origin of the linear magnetic susceptibility anomaly on Gallows Hill remains unknown, although geophysical surveys conducted for this thesis confirmed its existence and mapped it at a higher resolution than the 2013 survey. The results of the experimental research component do not support the conclusions drawn regarding the tentative identification of the linear anomaly as the palisade. In this case, it appears that traditional archaeological excavation may be the best method for determining the nature and significance of the linear anomaly. Excavation would inform the geophysical survey results, providing insight into the response of the EM38B to the trench feature, contributing to discussion on the effect of tightening magnetic susceptibility transect spacing for detecting features in archaeological mapping.