ICE AND FIRE | Geophysical survey results hint at archaeology


The geophysical survey conducted by AOC Archaeology Group, Alistair Galt pictured here, earlier this year has now been analysed. Magnetic susceptibility indicates areas where burning and disturbance has occured – from recent times but also into the more distant past. Work starts later this month to ground-test these areas of interest, and areas where surface finds of stone tools have been recovered.

Test pits, usually 0.5m² or 1m² will be excavated initially to identify areas of past human activity and ongoing potential for more detailed archaeological work. These will also help to distinguish archaeological potential from natural geological anomalies and more recent activity related to the repeated fires, footpaths, field boundaries, and erosion. We follow stratigraphy – distinct layers – from the surface to natural substrate and sieve everything to recover even the smallest finds. Any burnt material, usually charcoal, is carefully bagged in aluminium foil for possible radiocarbon dating where directly associated with human activity. We also take soil samples to analyse in more detail and to wet sieve in a controlled environment (called flotation) where charcoal floats and tiny artefacts are visible in the residues. Equally, any features such as stakeholes, postholes, hearths, or modified surfaces, are carefully recorded, 3D plotted, photographed, planned and sectioned.

© 2017 AOC Archaeology Group.

This example, above, of one of the interpreted geophysical results shows:

  • The possible archaeological features are anomalies with a strong magnetic response based either on their relationships to known topographic features, such as the depression in the north thought to be archaeological, or their unusual patterning which might suggest a possible archaeological source. At this stage it must be stressed that until more intrusive work is undertaken that these must be considered to be natural responses rather than definitive archaeology but we are more hopeful of these being archaeological.
  • The discrete linear trends identified in the geophysics have a more tentative positive or negative responses that are distinct from the background noise. These can mostly be seen in the aerial photography and LIDAR, which suggests they are related to these features.
  • The unclear trends have a weaker positive or negative response than the discrete linear trends and are more likely to be related to natural features, as no features can be seen in the basemap or the LIDAR.
  • The geology is identified as a highly magnetic background noise, and is extensive in the south eastern area in particular, probably as a result of the geology being closer to the surface. The modern disturbance is where a stronger dipolar response has been recorded and where the modern paths are known to be located. Likewise it must be stressed that the fire damage on the site may well have also added to these areas of disturbance and may well be the cause of both the geology and modern disturbance areas.

– ICE AND FIRE Project Team