Similar slopes of lines connecting δ18O and δ13C plots between co‐existing micrite and dolomite pairs are due to small inheritance effects on δ13C from dissolution of CaCC3and large variations in δ18O in dolomite due to dolomitizing fluids in a marine to mixing zone. The δ13C values of replaced precursor CaCO3were variable due to early meteoric diagenesis. Dolomite is in equilibrium with marine, mixed‐marine and meteoric CaCO3because dolomitization occurred when CaCO3was metastable, simultaneously with or slightly after the transformation of metastable CaCC3to calcite during early diagenesis. Recrystallization of dolomite involved the renewed growth of dolomite on early‐formed dolomite and the replacement of co‐existing CaCO3. This involved negligible depletion in δ13C and a small negative shift in δ18O.