Detecting Calcite Contamination on Cremated Remains from Balearic Lime Burials (Mallorca, Spain) through a Multi-Proxy Approach.

Abstract

Lime burials were a widespread funerary practice in the Balearic Islands during the Iron Age, involving the use of limestone at some stage of the cremation process. The presence of limestone has shown to alter carbon isotope composition, complicating radiocarbon dating. In cremated bone, carbon (δ13C) and oxygen (δ18O) isotopes, together with FTIR-ATR spectroscopy, provide insight into burning conditions and heat-induced changes in bone, while strontium isotopes and concentrations (δ88Sr, 87Sr/86Sr, [Sr]) assess individual mobility and diet. However, whether limestone affects the latter in lime burials, remains unknown. Twelve cremated bone fragments from the Iron Age site Cova des Robiols (Mallorca), were analysed before and after pre-treatment with acetic acid using FTIR-ATR spectroscopy, carbon (δ13C), oxygen (δ18O), and strontium (δ88Sr, 87Sr/86Sr, [Sr]) isotope analyses, to assess the impact of calcite-derived diagenesis on cremated bone. Results show that the current pre-treatment protocol for Sr analysis does not effectively remove calcite. Samples with Calcite to Phosphate (Cal/P) index values > 0.001 show wide variation in Sr concentrations, high δ88Sr values, and lower 87Sr/86Sr, closer to the limestone value (0.7079), alongside lower δ13C values. Samples with Cal/P values ≤ 0.001, in contrast, show δ88Sr values more consistent with biological apatite, and fall within expected local geological 87Sr/86Sr ranges. These findings demonstrate that a combined FTIR–multi-isotopic screening strategy can reliably distinguish between calcite-contaminated and not contaminated calcined bone remains, allowing unsuitable samples to be excluded before interpreting mobility patterns among Balearic protohistoric communities. In addition, a transferable tool for isotopic research on cremated remains from other carbonate-rich burial contexts is proposed.

Keywords

• calcined bone
• bone diagenesis
• FTIR-ATR
• carbon & oxygen isotope analysis
• strontium isotope analysis
• iron age
• balearic islands