The CALMARSII project aimed to improve the physical, chemical and biological understanding of the processes underlying proxy incorporation in skeletons, carry out a critical comparison and validation of different proxies and refine the use of calcareous marine skeletons for reconstruction of past salinity changes and continental weathering fluxes.By bringing together a multidisciplinary network of biologists, chemists,geologists and engineers, our objectives were to (i) address the mechanisms of proxy incorporation to gain insight into the robustness of several proxies stored in biogenic carbonates; and (ii) reconstruct past environmental conditions. Based on species/proxy combinations, we have developed a multi-proxy approach using different types of marine carbonate skeletons and associated organic matrix. These proxies include both well-established (d18O, d13C, Ba/Ca, Mg/Ca, Sr/Ca) and newly developed ones (dD, d26Mg).