Cathodoluminescence study of oyster shell growth modalities allows to propose a new method of investigation, which is less dependent on the conditions of preservation of fossilized shells conditions that the classical sclerochronological approach. Analysis by cathodoluminescence of sections of the hinge under the ligamental area of fossil oyster shells Crassostrea aginensis Tournouer, 1914 (Aquitanian) and Ostrea bellovacina Lamarck, 1806 (Thanentian) allowed to calculate the age based on the seasonal growth of shells, whereas the none preservation of the morphological marks of growth made a sclerochronologic analysis impossible. Moreover, this part of the shell seems the most reliable site to carry out geochemical analyses to characterize the record of palaeoenvironmental data by the biomineralization process of these organisms.