10:15 AM - 10:30 AM
[MIS25-06] Geologic evidence of tsunamis in Kujukuri
Keywords:Japan Trench, Tsunami deposit, Kujukuri
We have found two anomalous marine sand layers preserved in low-energy freshwater environments where they would not normally occur (i.e., present day rice paddies). The medium to coarse sand layers range in thickness from 3-10 cm, are intercalated with muddy peat, and the two upper layers can be traced 3.8 km inland and ~5 km along the present Kujukuri coastline near Sanmu City. The sand layers have features consistent with tsunami deposits found elsewhere, such as a distinct erosional base, marine geochemical signature, offshore foraminifera, rip-up clasts, normal grading, and a mud drape. Preliminary radiocarbon dating of seeds, charcoal and insect cuticles constrain the age of the upper sand to A.D. 1613 ? 1651. Possible candidates for the upper sand are the Genroku tsunami of A.D. 1703 and the Empo tsunami of A.D. 1677. The age of the bottom sand is A.D. 971 ? 1047, an age that coincides with an 11th century gap in the historical record.