Stable carbon and oxygen isotope geochemistry as provenance indicator for the picture stones on Gotland (Sweden)

ABSTRACT

The picture stones from Gotland are one of the most famous and exceptional groups of monuments known from Swedish Prehistory. These carved memorial stones and their extraordinarily rich imagery are a unique source for the study of Late Iron and Viking Age culture and in particular Scandinavian pre-Christian religions. The Gotlandic picture stones are mainly made from the thickly layered limestones surrounding the reefs and bioherms of Gotland’s carbonate platform from the middle part of the Silurian (latest Llandovery to Ludlow, Telychian – Ludfordian). However, the exact origins of the picture stones’ raw materials on Gotland have remained undetermined. In this paper, we investigate the geological origin of the raw material by isotope geochemistry. Whereas the oxygen (δ¹⁸O) and strontium isotope ratio (⁸⁷Sr/⁸⁶Sr) were strongly altered by diagenesis the carbon isotope ratio (δ¹³C) is quite stable. Because the different geological units on Gotland show specific isotope signatures, the δ¹³C values from picture stones can be used to assign them to the respective geological unit, and thus to the source area of the raw material. This also allows for an estimation of transport distance minima between the raw material source area and the find place of each sampled picture stone. Most of the picture stones seem to be produced from local material with short transport distances, less than 10 km and only a few were transported at a far distance exceeding 10 km. In summary, the transport distance was dependent mostly on the local availability of picture-stone-suitable rocks.

KEYWORDS:

• Carbon isotopes
• Gotland
• Iron Age
• oxygen isotopes
• picture stones
• strontium isotopes
• transport distances

Acknowledgements

Many thanks go to Michael M. Joachimski and Daniele Lutz, both at GeoZentrum Nordbayern (GZN), Erlangen (Germany), for measuring the carbon and oxygen isotope samples. In addition, we are grateful to Marcel Regelous, also at GZN, for measuring the strontium isotope values from the chosen field isotope samples. Many thanks go also to Anna Lene Claußen (GZN) for helping by the organizations of the field trips to Gotland in September 2018 and in September 2019, and to Birgit Leipner-Mata (GZN), for helping with the sample preparation. We are also grateful to Johan Norderäng at Gotlands Museum, Visby (Sweden), for help in the administrative part for the picture stones which were sampled for our study. Many thanks go to Alexander Andreeff Högfeldt and to an anonymous reviewer for the reviews and helpful comments on this work. We are also grateful to Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for the financial support of our project ‘Microfacies and stable isotopes of the picture stones on Gotland - a new approach for investigating the origin of the initial material’ (project number Mu 2352/7-1) in which our work is part of it. This work was in cooperation with Ancient Images 2.0 – A digital edition of the Gotlandic picture stones. https://www.ancientimages.se/.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [project number Mu 2352/7-1].