W. Derek Hamilton

Deciphering diet and monitoring movement: Multiple stable isotope analysis of the viking age settlement at Hofstaðir, Lake Mývatn, Iceland.

OBJECTIVES A previous multi-isotope study of archaeological faunal samples from Skútustaðir, an early Viking age settlement on the southern shores of Lake Mývatn in north-east Iceland, demonstrated that there are clear differences in δ(34)S stable isotope values between animals deriving their dietary protein from terrestrial, freshwater, and marine reservoirs. The aim of this study was to use this information to more accurately determine the diet of humans excavated from a nearby late Viking age churchyard. MATERIALS AND METHODS δ(13)C, δ(15)N, and δ(34)S analyses were undertaken on terrestrial animal (n = 39) and human (n = 46) bone collagen from Hofstaðir, a high-status Viking-period farmstead ∼10 km north-west of Skútustaðir. RESULTS δ(34)S values for Hofstaðir herbivores were ∼6‰ higher relative to those from Skútustaðir (δ(34)S: 11.4 ± 2.3‰ versus 5.6 ± 2.8‰), while human δ(13)C, δ(15)N, and δ(34)S values were broad ranging (-20.2‰ to -17.3‰, 7.4‰ to 12.3‰, and 5.5‰ to 14.9‰, respectively). DISCUSSION Results suggest that the baseline δ(34)S value for the Mývatn region is higher than previously predicted due to a possible sea-spray effect, but the massive deposition of Tanytarsus gracilentus (midges) (δ(34)S: -3.9‰) in the soil in the immediate vicinity of the lake is potentially lowering this value. Several terrestrial herbivores displayed higher bone collagen δ(34)S values than their contemporaries, suggesting trade and/or movement of animals to the region from coastal areas. Broad ranging δ(13)C, δ(15)N, and δ(34)S values for humans suggest the population were consuming varied diets, while outliers within the dataset could conceivably have been migrants to the area.

The myths and realities of Bayesian chronological modeling revealed

We review the history of Bayesian chronological modeling in archaeology and demonstrate that there has been a surge over the past several years in American archaeological applications. Most of these applications have been performed by archaeologists who are self-taught in this method because formal training opportunities in Bayesian chronological modeling are infrequently provided. We define and address misconceptions about Bayesian chronological modeling that we have encountered in conversations with colleagues and in anonymous reviews, some of which have been expressed in the published literature. Objectivity and scientific rigor is inherent in the Bayesian chronological modeling process. Each stage of this process is described in detail, and we present examples of this process in practice. Our concluding discussion focuses on the potential that Bayesian chronological modeling has for enhancing understandings of important topics. En este artículo se reseña la historia de la modelización cronológica bayesiana en arqueología y se demuestra que en los últimos años arqueología americana ha experimentado un auge en su aplicación. La mayor parte de los análisis han sido desarrollados por arqueólogos que son autodidactas en el aprendizaje del método, ya que las oportunidades de formación en el análisis bayesiano son muy limitadas. Se explica cuáles son los errores más comunes en la aplicación de la modelización cronológica bayesiana, algunas de los cuales ya han sido señaladas en otros trabajos, que hemos encontrado al conversar con compañeros y en revisiones anónimas. La objetividad y el rigor científico resultan inherentes al proceso de modelización cronológica bayesiana. Se describe en detalle cada etapa de este proceso, presentando ejemplos de su puesta en práctica. Nuestra conclusión se centra en torno al potencial de este método para mejorar nuestra comprensión sobre temas de gran relevancia.

Stable isotopes, chronology and Bayesian models for the Viking archaeology of north-east Iceland

ABSTRACT This paper reviews the results of a long-term research project that used stable isotope analyses (δ13C, δ15N, δ34S) and Bayesian mixing models to better model the chronology for a presumed Viking Age cemetery at Hofstaðir, near Lake Mývatn in north-east Iceland. δ13C and radiocarbon dating indicated that many of the individuals consumed a large amount of marine protein, which results in a marine reservoir effect (MRE), making ages older than expected. In addition to the MRE, geological activity in the region has the potential to introduce massive quantities of radioactive ‘dead’ carbon into the freshwater system, resulting in a very large freshwater reservoir effect (FRE) that can offset radiocarbon ages on the order of a few thousand years. The radiocarbon dates of organisms that derive an unknown proportion of their carbon from both marine and freshwater reservoirs are extremely difficult to ‘correct’, or, more appropriately, model. The research not only highlights the complexities of dealing with multiple reservoirs, but also how important it is to develop models that are temporally and geographically relevant to the site under study. Finally, it shows how this data can be used to inform the development of chronological models for refining the dating for archaeological activity.