The potential of combined Mg/Ca and δ18O measurements within the shell of the bivalve Pecten maximus to estimate seawater δ18O composition

► Study of Mg/Ca and δ18O in Pecten maximus as temperature and seawater δ18O proxies. ► Mg/Ca in the inner shell was strongly related with temperature (r2 = 0.77). ► Seawater δ18O estimated with accuracy of 0.15‰ and uncertainty of 0.35 or 0.63‰. ► Mg/Ca and δ18O in P. maximus are potential proxies for seawater temperature and δ18O.