An initial attempt to date Pleistocene marine terraces in the south coast of Japan using in situ cosmogenic 10Be and 26Al

Abstract

The southern coasts of Shikoku Island and the Kii Peninsula are located along the Nankai Trough where the Philippine Sea Plate is subducting under the Eurasian plate in Japan. Relatively well-preserved marine terraces along the coast, with elevations ranging between ca. 50 and 100 m, are suitable counterparts to reconstruct the uplift history of the southwestern coast of Japan due to the unique tectonic setting. In this study, we attempt to determine the age of the marine terraces by employing in-situ terrestrial cosmogenic radionuclides (TCN), 10Be and 26Al. TCN depth profiles provide information on the timing of terrace formation. General agreement between our TCN chronology and the existing tephrochronology show that the TCN method can be applicable to a mid-latitude coastal setting where erosion must also be considered. Thus, measuring TCN on uplifted terraces around Japan can be a promising technique for clarifying uplift rates and the seismic history of the region.