Sourcing fire ash on archaeological sites in the Western and Northern Isles of Scotland, using mineral magnetism

Abstract

The application of a new technique developed to identify different fuel sources from ash on nine archaeological sites in the Western and Northern Isles of Scotland is presented. The technique is based on variations observed in the mineral magnetic signatures that derive from the experimental burning of different fuels. The application of the technique is successful, demonstrating both uniformity and diversity in fuel use. A marked continuity of practice in fuel procurement is apparent over thousands of years from seven sites in Lewis, with well-humified peat the dominant fuel source. This implies a long-term stability in the division and tenure of the peatlands. Greater magnetic variation is displayed by the samples from Cladh Hallan, South Uist and Scatness, Shetland, suggesting more diverse fuel procurement strategies were in operation at these sites. The uniformity and diversity in fuel types also has implications in terms of the residuality of plant remains from the fuel source within archaeobotanical assemblages recovered from the sites.