Our Bones, who art contaminated : Glues, strontium isotopes, and mobility in early Swedish Christians

Abstract: This thesis aims to build upon previous research into contamination and its effects on isotopes by focusing on the strontium isotopic ratio (87Sr/86Sr), which is used in mobility studies to study the movements of past humans and animals and to build past economic trading networks. Contamination is a broad topic, and in the scope of this thesis, it concerns the introduction of contaminants from the soil after interment and the post-excavation preservation efforts. Due to these effects, this thesis analyzed three types of adhesives and consolidants that were or are still in use. These include strontium-containing glues, specifically animal-based glues, as well as “Karlsons klister,” which was identified as polyvinyl acetate, and epoxy resins. The latter are used to stabilize and mount small materials, such as otoliths. In addition, this thesis aims to focus on the methodological development of pretreatment methods for bones, using the Swedish Early Christians as a focus and comparing the results to the tooth enamel of the same individuals.The Christianization period in Sweden overlaps the Late Viking Age and the Early Medieval period, between the 8th and the 11th centuries. This period saw dynamic changes, which initiated the movement of people to Christianized areas. Two sites were the primary focus of this thesis, Varnhem in southwestern Sweden, which contains one of the earliest Christian communities in Sweden, and Västerhus, a well-studied site in northern Sweden, which was constructed during a period of rapid infrastructure growth. These two sites not only differ in period of use, and cemetery size, but also in regard to whether individuals were local or non-local based on their 87Sr/86Sr results. In addition, this thesis introduces the differences in individual diets using carbon, nitrogen, and sulfur. Four experiments were conducted for this thesis: two were manual contamination experiments on uncontaminated modern skeletal tissues, horse bone and cod otoliths, which were contaminated with animal-based glues and epoxy resin, respectively. These experiments tested the effects of the contamination on the biogenic 87Sr/86Sr values. The final two experiments focused on the two early Christian sites and evaluated these individuals' mobility using their enamel and bone. The enamel recorded the intra-individual strontium consumption during tooth formation so that they could be aged to site arrival. The bones from these sites were tested for diagenesis, and the coating on the Västerhus bones was identified. Then the efficacy of two pretreatment methods was tested against these types of contamination.The adhesives produced varying effects on the 87Sr/86Sr values. The strontium-containing glues affected the biogenic values of the horse bone, the resin did not appear to affect the otolith values, and the “Karlsons klister” did not appear to affect the 87Sr/86Sr values in the Västerhus bones. Neither the ashing nor the washing method effectively removed the contamination from the animal-based glues; however, it did appear to affect the values in the diagenetically altered bones.