A Chronology for a Massacre : Bayesian C-14 Analysis of the Archaeological Record from Sandby Borg, Öland

Abstract: This thesis addresses radiocarbon (C-14) dating of bioarcheological finds from Sandby borg, an iron-age ring fort on the east coast of the Baltic Sea island of Öland, Sweden. Archaeological evidence suggests that Sandby borg was used during the European migration period and that its main period of usage was terminated by an isolated incidence of inter-personal violence where the inhabitants were killed or abducted. Radiocarbon dating of individual archaeological finds from this period becomes imprecise due to fluctuations of C-14 ratios in the atmosphere during the period 420-530 AD. In the work presented here, Bayesian modelling, whereby multiple finds as well as chronological information from typology and stratigraphy are combined into a statistical model is deployed, together with an estimate of the percentage of maritime products in the diet of individuals subjected to C-14 dating. The outcome of this analysis suggests that the usage ranges from 410-537 AD (95.4% probability) and that the lethal attack took place between the years 532 and 558 AD (95.4% probability). This latter dating interval is about 40-60 years later than what has been suggested from previous studies. The reliability of the modified chronology and its consequences for our understanding of the Sandby borg site is discussed, and some future directions of research are proposed.