Isotope values of the bioavailable strontium in inland southwestern Sweden—A baseline for mobility studies

Abstract

The inland area of southwestern Sweden is well known for its well-preserved archaeological animal and human remains dating back to the Mesolithic and Neolithic (10000–4000 and 4000–1700 BC). They allow application of multiple bioarchaeological methods, giving insights into various and complementary aspects of prehistoric human life, as well as economic and social structures. One important aspect concerns human mobility and its relation to social networks and to circulation of objects. Here, strontium isotope analysis plays a crucial role. The present study aims to construct a strontium isotope baseline of southwestern Sweden with considerably greater coverage and higher resolution than previously published data. As the region has been affected by glacial events, the relation between bedrock geology and isotope signals of the bioavailable strontium in such areas is given special attention. We determined strontium isotope ratios for 61 water and five archaeological animal samples, and combined the data with previous measurements of two water and 21 non-domestic faunal samples. The results reveal a complex pattern. Several areas with distinct baseline ranges can be distinguished, although with overlaps between some of them. Overall, the bioavailable strontium isotope signals mirror the basement geology of the region. The highest ratios occur in the geologically oldest eastern parts of the Precambrian terrain, while lower ratios are found in the western part, and the lowest ratios occur in the youngest Paleozoic areas. At the same time, there are minor deviations compared to the underlying bedrock, due to glacial transport, overlying sediments, and local intrusions of younger rocks. The background data set now available allows for more nuanced and detailed interpretations of human and animal mobility in the region, in particular by identification of subregions with differing strontium isotope ratios within the Precambrian province. Also, we can now identify long distance mobility with greater confidence.

Mobility patterns in inland southwestern Sweden during the Neolithic and Early Bronze Age

“…This investigation builds on a recently published Sr isotope baseline study of inland southwestern Sweden (Blank et al 2018a). It confirmed that the different proxies for the isotope composition of the bioavailable Sr in general mirror the basement geology, although some effects of glacial transport, overlying sediments and local intrusions of younger rocks were observed.…”

“…2). According to the baseline model proposed by Blank et al (2018a), the low 87 Sr/ 86 Sr ratios of Falbygden extend towards the south-southwest, which corresponds with the general direction of movement of the glacial ice in this region (Påsse and Pile 2016).…”

“…The term Falbygden is here used in an expanded sense and encompasses the entire Cambro-Silurian sedimentary zone, which is surrounded by Precambrian crystalline rocks. Previous research (Blank et al 2018a;Blank and Knipper in press;Sjögren et al 2009; Sjögren and Price 2013a) has demonstrated a clear distinction between the Sr isotope ratios in the Cambro-Silurian and the Precambrian regions. Thus, the geological conditions of Falbygden provide an ideal setting for mobility studies based on Sr isotopes.…”

“…Thus, the geological conditions of Falbygden provide an ideal setting for mobility studies based on Sr isotopes. A recent Sr isotope baseline (Blank et al 2018a) of the inland of southwestern Sweden allows more elaborate discussions of mobility patterns. Furthermore, the calcareous soils are favourable for bone preservation, and a remarkable assemblage of wellpreserved archaeological animal and human remains has been recovered from the megalithic graves.…”

Coalescing traditions—Coalescing people: Community formation in Pannonia after the decline of the Roman Empire

“…The classification of 87 Sr/ 86 Sr ratios as non-local requires comparative data that characterize the isotope ratios of the biologically available strontium. Samples to establish Sr isotope baselines can include enamel of supposedly locally fed animals from archaeological contexts, modern water or vegetation as well as archaeological bones [43][44][45][46][47].…”