Reservoirs and radiocarbon: 14 C dating problems in Myvatnssveit, Northern Iceland

• Main Authors: Ascough, P.L., Cook, G.T., Church, M.J., Dugmore, A.J., McGovern, T.G., Dunbar, E., Einarsson, E., Frioriksson, A., Gestsdottir, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2007
• Subjects: QE Geology; GE Environmental Sciences; Mývatn; Iceland; North Atlantic
• Online Access: https://eprints.gla.ac.uk/5020/; https://eprints.gla.ac.uk/5020/1/id5020.pdf; http://www.radiocarbon.org/

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (~AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14 C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14 C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new ΔR values for the north coast of Iceland, indicating a ΔR of 106 ± 10 14 C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean ΔR of 111 ± 10 14 C yr. The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14 C yr, where the fish are depleted in 14 C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO 2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14 C activity of samples influenced by groundwater at Icelandic archaeological sites.