Fish Reservoir Effect on Charred Food Residue 14C Dates: Are Stable Isotope Analyses the Solution?

Abstract

In order to verify the relative dating based on pot type morphology and decoration of the Swifterbant pottery collected at the Final Mesolithic site of Doel "Deurganckdok" (Belgium) and of the Late Iron Age pottery excavated at Grijpskerke (the Netherlands), direct radiocarbon dates were obtained on charred food residue preserved on the inner surface of numerous potsherds. In addition, a number of indirect 14C dates were obtained from samples of organic material. In the case of Doel, the results indicate an important incompatibility between the charred food residue dates and the other dates, the former being systematically older. This difference may be explained by a reservoir effect of the charred food residue, caused by the processing of (freshwater) fish. The 14C dates for the rijpskerke site are in agreement between the charred food residue and the organic material. The stable isotopes of the charred food residue were analyzed to demonstrate fish processing in the pottery, but the results were inconclusive.