Radiocarbon Dating

Abstract

Radiocarbon ages should never be considered in isolation. The nature of the sample material, its environment and history, as well as the measurement techniques all play a part and need to be evaluated carefully in the interpretation of the ages. The carbonaceous material on which the radiocarbon isotope concentration measurements are made is the final product of photosynthesis of contemporary atmospheric carbon dioxide preserved in the sedimentary sequence. Its position in the stratigraphical column in normal circumstances allows the relative ages of the stratigraphical units to be assessed. The determinations are made on the assumption that the samples measured are related directly or indirectly to some event the age of which is required in the investigation. Rarely is it that the age of the material itself is of intrinsic interest. It is therefore most important that the provenance of the sample is thoroughly examined and the manner in which the material reached the situation in which it was discovered is important. The subsequent possible disturbance of the sample and particularly the possibilities of its being contaminated by one or more carbon-bearing materials of different age must be assessed. In particular the geological and geochemical conditions of the sample environment are of critical importance in leading to a correct age interpretation. The environment of the carbonaceous samples from Holywell Coombe is unusual and extreme because of the highly calcareous nature of the deposits. This is an important consideration in the evaluation of the ages obtained and for this reason is discussed further.