Defining local 87Sr/86Sr baselines using high-resolution bioavailable strontium isoscapes: Implications for short-range prehistoric mobility in southwestern Iberia

Radiogenic strontium isotope ratios ( 87 Sr/ 86 Sr), together with aDNA analyses, constitute one of the few approaches capable of reliably reconstructing ancient human and animal mobility. Interpreting mobility patterns, however, requires a robust characterisation of bioavailable 87 Sr/ 86 Sr signatures at appropriate spatial scales. This study presents the first high-resolution bioavailable strontium isoscape for southwestern Iberia, constructed from environmental samples—including soils leachates, tree leaves, and ground vegetation—collected between the Middle Guadiana and the Lower Guadalquivir valleys, a region characterised by pronounced geological heterogeneity. The resulting isoscape captures micro-geological and micro-geographical variability and is used to define local 87 Sr/ 86 Sr baselines that are subsequently applied to mobility analyses at seven Chalcolithic archaeological sites. Catchment-area baselines derived from isoscape predictions complement those established from archaeological enamel of domestic fauna. In addition, integrating mobility cost-surface analyses and corridor modelling enhances the reconstruction of human movement, landscape interaction, and animal herding strategies. The combined use of environmental isoscape data, human and faunal enamel values, and landscape-based mobility modelling provides a robust and transferable framework for refining interpretations of short-range prehistoric mobility.