ESR dating of Soma (Manisa, West Anatolia – Turkey) fossil gastropoda shells

Electron spin resonance (ESR) spectroscopy technique has been employed to date the aragonitic fresh-water gastropod shells (Melanoides curvicosta) collected from Soma (Manisa) district (West Anatolia) of Turkey. The influence of the annealing temperature and γ-radiation dose on dating signal at g = 2.0016 is investigated. The thermal stability and dose response of the ESR signals were found to be suitable for an age determination using a signal at g = 2.0016. The activation energy (E), frequency factor (s) and mean-lifetime (τ) at 15 °C of the g = 2.0016 center were calculated to be 1.67 ± 0.01 eV, (3.6 ± 0.7) × 1013 s−1 and 2.02 × 108 years, respectively. The ESR signal growth curve on additional γ-irradiation has been best fitted by an exponential saturation function. Based on this model, accumulated dose (AD) value for dating is obtained. We have determined the ESR age of the terrestrial gastropods to be 2.57 ± 0.30 Ma. The results show that the ESR age falls into the Late Pliocene (Romanian) epoch of the geological time scale, which agreed with the paleoecological and paleogeographic distribution and stratigraphic level of the fauna.