ESR DATING OF QUARTZ AND PLAGIOCLASE FROM VOLCANIC ASHES USING E'1, AL AND TI CENTERS

Two volcanic ash layers named Kasuri and Sakura in the Osaka Group were dated by electron spin resonance (ESR). The obtained equivalent dose (ED) using ESR signal intensity of Ti centers was larger than the one using Al centers for plagioclase in Kasuri ash layer. An annealing experiment indicates that artificial gamma-ray irradiation produces unstable Al centers as well as stable ones in plagioclase, while both stabilities of Ti centers in irradiated and in non-irradiated aliquots are the same. The age obtained using Ti centers in plagioclase is consistent with the stratigraphy and fission track (FT) ages. The obtained total accumulated doses using E', Al and Ti centers were consistent for quartz in Sakura ash layer. The termal stability of E' centers is also investigated by an annealing experiment.