Agricultural lime disturbs natural strontium isotope variations: Implications for provenance and migration studies

Abstract

Agricultural liming severely affects the use of strontium isotopes in prehistoric provenance and migration studies.

Abstract

The application of ⁸⁷Sr/ ⁸⁶Sr in prehistoric mobility studies requires accurate strontium reference maps. These are often based from present-day surface waters. However, the use of agricultural lime in low to noncalcareous soils can substantially change the ⁸⁷Sr/ ⁸⁶Sr compositions of surface waters. Water unaffected by agriculture in western Denmark has an average ⁸⁷Sr/ ⁸⁶Sr ratio of 0.7124 as compared to an average of 0.7097 in water from nearby farmland. The ⁸⁷Sr/ ⁸⁶Sr ratio obtained from samples over 1.5 km along a stream, which originates in a forest and flows through lime-treated farmland, decreased from 0.7131 to 0.7099. Thus, ⁸⁷Sr/ ⁸⁶Sr-based mobility and provenance studies in regions with low to noncalcareous soils should be reassessed. For example, reinterpreting the iconic Bronze Age women at Egtved and Skrydstrup using values unaffected by agricultural lime indicates that it is most plausible that these individuals originated close to their burial sites and not far abroad as previously suggested.