EAA 2022: Abstract

Little is known about how peat fires influence the preservation and stable isotope values of cereal grains recovered from archaeological hearths. Stable carbon and nitrogen isotope ratios (δ13C, δ15N) can be used to reconstruct agrarian practices from these grains. Therefore, a series of archaeological experiments with peat hearths was conducted, adding a set number of grains of Bere barley, an Atlantic Scottish landrace, to each hearth. The experiments simulated Iron Age (IA) charring conditions in Atlantic Scotland, and the results were applied to archaeological barley grains from Clachtoll broch, Sutherland. Overall, the preservation of the experimental grains was poor except for one perfectly preserved grain. This matches archaeobotanical preservation profiles from IA Atlantic Scottish cereal assemblages. The experiments show a significant increase in δ15N values for the poorly-preserved cereal grains in the experimental hearths. A decrease in grain size and preservation were found to be correlated, as were preservation and an increase in δ15N. Therefore, it is proposed that only very well-preserved cereal grains (P1-P3 following Hubbard and al Azm 1990) charred by peat fires should be used for stable isotope analysis in reconstructing ancient land management strategies in Atlantic Scotland and the wider North Atlantic region. Our archaeological application of the experimental findings to the barley grains at Clachtoll broch, produced an average δ15N value of 5.30±1.70‰ from 100+ grains, indicating that they were grown in fields with significant anthropogenic amendment.

experimental archaeology, stable isotopes, Iron Age, Scotland, peat hearths, Bere barley

Oral presentation

  Abstract (PDF)

Fiona Walker-Friedrichs²

Darren Gröcke²
Andy Heald¹
Graeme Cavers¹
Jackaline Robertson¹
Mike Church²