Strontium isotope identification of possible rural immigrants in 17th century mass graves at St. Gertrude Church cemetery in Riga, Latvia

Abstract

The aims of this study were to explore the origins of 19 children buried in two mass graves and the general cemetery at the post-medieval St Gertrude Church cemetery in Riga, Latvia, using strontium isotope analysis (87Sr/86Sr), and to establish local soil Sr biosphere ranges from faunal samples from two areas of Latvia. The results confirmed the presence of one clear outlier in the population and one child who may have had originated from the region of Vidzeme. The lack of significant differences in 87Sr/86Sr between the other individuals analysed suggested that they were representative of one population. A strong correlation between 87Sr/86Sr ratios and previously obtained mean δ13C and δ15N values in children from mass graves suggested possible short-term dietary changes with increased proportion of marine resources and food sources subject to sea spray. The study has yielded the first comparative 87Sr/86Sr data from archaeological skeletons in Latvia, which will be essential for future research addressing comparative mobility studies in the region.