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

Abstract

The application of 87 Sr/ 86 Sr 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 87 Sr/ 86 Sr compositions of surface waters. Water unaffected by agriculture in western Denmark has an average 87 Sr/ 86 Sr ratio of 0.7124 as compared to an average of 0.7097 in water from nearby farmland. The 87 Sr/ 86 Sr 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, 87 Sr/ 86 Sr-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.