Reservoirs and Radiocarbon: 14 C Dating Problems in Mývatnssveit, Northern Iceland

• Published in: Radiocarbon
• Main Authors: Ascough, Philippa L, Cook, Gordon T, Church, Mike J, Dugmore, Andrew J, McGovern, Thomas H, Dunbar, Elaine, Einarsson, árni, Frioriksson, Adolf, Gestsdóttir, Hildur
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2007
• Subjects: Mývatn; Iceland; North Atlantic
• Online Access: http://dx.doi.org/10.1017/s0033822200042818; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822200042818

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 14 C 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.