Isotopic composition of Conomurex fasciatus shells as an environmental proxy for the Red Sea

Raman spectroscopy results on modern C. fasciatus shell samples show these specimens to be aragonitic. Ground fragments from archaeological C. fasciatus shells used for isotope analyses were also measured by Raman spectroscopy and shown to be well preserved against diagenetic alterations leading to aragonite to calcite transformation. Measured shell-edge δ18O values range from −0.5‰ to −1.7‰. Calculated modern shell edge temperatures from these δ18O values correlate with modern SST measured on site with an error of ±2.4 °C. Two different growth rates occurred in the shells of C. fasciatus. The measurement of growth increments in the lip part of adult specimens indicates a tide-related growth rate of ∼13 mm/year. Sequential δ18O data from juvenile parts of the shell indicates a faster growth rate of ∼90 mm/year. This growth rate and the correlation of δ18O with measured temperatures allows the use of C. fasciatus shell δ18O as a palaeoclimate proxy.