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

• Main Authors: Ascough, P. L., Cook, G. T., Church, M. J., Dugmore, A. J., McGovern, T. H., Dunbar, E., Einarsson, Á., Friðriksson, A, Gestsdóttir, H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: University of Arizona 2007
• Subjects: Marine reservoir effect; Freshwater reservoir effect; Norse period; North Iceland; Mývatnssveit; Mývatn; Iceland; North Atlantic
• Online Access: http://dro.dur.ac.uk/5227/; http://dro.dur.ac.uk/5227/1/5227.pdf; http://www.radiocarbon.org/

This paper examines two potential sources of the 14C offset between human and terrestrial mammal (horse) bones recovered from Norse (c.870-1000 AD) pagan graves in Mývatnssveit, North Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine reservoir 14C effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusc shell) at two archaeological sites in Mývatnssveit and one on the North Icelandic coast. These produced three new ΔR values for the North coast of Iceland, indicating a ΔR of +106 ± 1014C yr at 868-985 AD, and of +144 ± 2814C yr at 1280-1400 AD. These values are statistically comparable and give an overall weighted mean ΔR of +111 ± 1014C 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 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude that: 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 14C activity of samples influenced by groundwater at Icelandic archaeological sites.