Multi-regional calibration of Patella caerulea as a palaeothermometer using oxygen isotope values and Mg/Ca ratios

Abstract

This study presents a comprehensive calibration of the Patella caerulea as a palaeotemperature archive across the Central and Eastern Mediterranean, focusing on Mg/Ca ratios and δ¹⁸O values. We analysed 131 modern specimens collected from 22 localities, with a focus on the Aegean region. Our results demonstrate strong correlations between Mg/Ca ratios and the temperature proxy δ¹⁸O_shell, with a mean R² value of 0.89. These findings reinforce the utility of Mg/Ca as a reliable, though specimen-specific, proxy for relative SST variations, supporting its role in reconstructing seasonal temperature patterns and revealing areas of interest for subsequent methods. Additionally, oxygen isotope data from both shells and water samples at selected sites agreed well with element chemical data (Mg/Ca), confirming the usefulness of SST estimates based on δ¹⁸O values as well as the season of death in ~80% of studied specimens. Findings of the present study enhance our understanding of the applicability of P. caerulea as a palaeotemperature archive and provide a robust baseline for future palaeoclimate studies in Mediterranean archaeological contexts.