Application of 34S analysis for elucidating terrestrial, marine and freshwater ecosystems: Evidence of animal movement/husbandry practices in an early Viking community around Lake Myvatn, Iceland

摘要

Carbon and nitrogen stable isotope ratios (δ~(13)C and δ~(15)N) have been used widely in archaeology to investigate palaeodiet. Sulphur stable isotope ratios (δ34S) have shown great promise in this regard but the potential of this technique within archaeological science has yet to be fully explored. Here we report δ~(34)S, δ~(13)C and δ~(15)N values for 129 samples of animal bone collagen from Skútusta{eth}ir, an early Viking age (landnám) settlement in north-east Iceland. This dataset represents the most comprehensive study to date of its kind on archaeological material and the results show a clear offset in δ~(34)S values between animals deriving their dietary resources from terrestrial (mean=+5.6±2.8‰), freshwater (mean=-2.7±1.4‰) or marine (mean=+15.9±1.5‰) reservoirs (with the three food groups being significantly different at 2σ). This offset allows reconstruction of the dietary history of domesticated herbivores and demonstrates differences in husbandry practices and animal movement/trade, which would be otherwise impossible using only δ~(13)C and δ~(15)N values. For example, several terrestrial herbivores displayed enriched bone collagen δ~(34)S values compared to the geology of the Lake Myvatn region, indicating they may have been affected by sea-spray whilst being pastured closer to the coast, before being traded inland. Additionally, the combination of heavy δ~(15)N values coupled with light δ~(34)S values within pig bone collagen suggests that these omnivores were consuming freshwater fish as a significant portion of their diet. Arctic foxes were also found to be consuming large quantities of freshwater resources and radiocarbon dating of both the pigs and foxes confirmed previous studies showing that a large freshwater radiocarbon (~(14)C) reservoir effect exists within the lake. Overall, these stable isotope and ~(14)C data have important implications for obtaining a fuller reconstruction of the diets of the early Viking settlers in Iceland, and may allow a clearer identification of the marine and/or freshwater ~(14)C reservoir effects that are known to exist in human bone collagen.