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

Abstract

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 freshwater14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine14C 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 ± 1014C yr at AD 868–985, and of 144 ± 2814C yr at AD 1280–1400. 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 183014C yr, where the fish are depleted in14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2into 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 the14C activity of samples influenced by groundwater at Icelandic archaeological sites.