An equation that relates the oxygen isotope ratio of the aragonite to sea surface temperature and the oxygen isotope ratio of the water was developed by Grossman and Ku (1986). This is a slightly modified form.
d18Oc(PDB) is the oxygen isotope ratio of the carbonate relative to the Pee Dee Belemnite standard, d18Ow(PDB) is the oxygen isotope ratio of the water relative to the Pee Dee Belemnite standard, and SST is the sea surface temperature. d18Ow(PDB) can be changed to the SMOW (Standard Mean Ocean Water) scale by adding 0.22. d18Ow(SMOW) is related to salinity by the equation
Using modern temperature and salinity observations from Cedar Key, this equation can be used to produce a predicted oxygen isotope ratio curve for moderncampechiensis shells.