An Investigation of the Ability of Geophysical Methods to Detect and Define Fulachta Fia (Burnt Mounds) on Clare Island, Co. Mayo, Ireland.

Measurements of electrical resistivity and magnetic susceptibility have been made in order to determine the geophysical signature of a number of fulachta fia (burnt mounds of probable Bronze Age) on Clare Island, County Mayo, Ireland. Visible remains of fulachta fia on Clare Island frequently show a characteristic horseshoe-shaped structure at the surface, covered by a very thin layer of topsoil. Magnetic susceptibility and electrical resistivity surveys over two intact fulachta fia were carried out in order to map their lateral and vertical extent. The magnetic susceptibility surveys provided horseshoe-shaped signatures, which immediately identify the extent and orientation of both the surveyed monuments. The success of the resistivity method was found to be dependant upon the proximity of unwanted sources of resistivity variation not related to these archaeological targets, and possibly climatological and method-related influences. These results illustrate the feasibility of using geophysical methods to define a characteristic signature related to fulachta fia. The reproduction of this signature over suspected archaeological sites can provide confirmation of the existence of a monument without the need for an intrusive excavation. Resistivity surveys over two damaged fulachta fia partially exposed in the bank of a drainage channel have revealed useful information on the degree of preservation of these monuments. Resistivity anomalies were identified coincident with the location of fractured rock exposed in the channel bank, despite the terrain effect caused by the proximity to the channel edge