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Keywords:

  • imaging;
  • linear earthwork;
  • Mull of Galloway;
  • promontory fort;
  • pseudosection;
  • resistivity

Abstract

Resistivity imaging was carried out over two linear earthworks that cut off a peninsula at the neck of the Mull of Galloway. The geophysical work formed part of a wider research programme, funded by Historic Scotland, involving excavation and survey, designed to assess the extent of erosion to the site. The southern (inner) line of earthworks is ca. 440 m long, whereas the northern (outer) earthwork measures only ca. 120 m. Both survive as turf and gorse covered, upstanding banks and ditches. Four resistivity images were taken across the earthworks. A further image was placed just to the south of the southern earthwork in an attempt to trace cobbles identified during excavation. The surveys used a Geopulse Imager system with 25 electrodes and an interelectrode spacing of 1 m, and apparent resistivities were acquired with the Wenner configuration. Topographic corrections were applied to the 22-m-long pseudosections, which were then inverted using Res2DInv to obtain resistivity models. Excavation of trenches through the earthworks confirmed that the resistivity models had been successful in providing an accurate picture of the character and construction of these rampart and ditch systems. Copyright © Crown Copyright 2001. Recorded with the permission of the controller of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.