Surface exposure ages of middle–late Pleistocene marine and fluvial terraces along the northern and southern Sanriku coasts, Northeast Japan

Abstract

To estimate long-term rates of coastal uplift along the northern Pacific coast of Northeast Japan, we determined the surface exposure ages of marine and fluvial terraces based on terrestrial in situ cosmogenic radionuclide dating of exposed bedrock surfaces. Based on reinterpretation of marine and fluvial terraces, we collected samples from the northern and southern Sanriku coast. The surface exposure ages from ¹⁰Be concentrations in quartz calculated from the measured ¹⁰Be/⁹Be ratios commonly suggest MIS 5 and MIS 7 for the marine and fluvial terraces and averaged coastal uplift rates of ca. 0.25 ± 0.15 and 0.4 mm/yr along the northern and southern Sanriku coast at intermediate timescales. The results may demonstrate different styles of crustal strain accommodation in the northern Northeast Japan arc above the subducting Pacific plate.