Marine reservoir effects in early Christian graves from Norway

Abstract We investigated radiocarbon dates of human bone samples from several medieval sites in Trondheim, central Norway. Stable isotope data was used to estimate marine correction for the radiocarbon dates, which is necessary to correct the radiocarbon ages and establish age models for the archaeological layers. We observed that a marine correction without ΔR does not lead to a well-defined model for all sites. Allowing a variable ΔR improves the model, which indicates that food sources and trade routes have changed over time, influencing the mobility of food resources as well as of people. However, this does not work for all sites, indicating that variation of reservoir ages could also be the result of individual preferences for the food and that fish with different ΔR, and thus different geographical origin, was consumed during the same periods. Many radiocarbon and stable isotope (δ 13 C, δ 15 N) measurements have been carried out for the project. We calculated %marine consumption from the isotope values and found that it varies greatly, between 7% and 51%, and apparently independent of period, social status, churchyard location or other factors. Based on these data, we determined average reservoir ages for the marine food consumed in Trondheim during different phases, varying between ΔR = –150 and 280 years.