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[MIS11-05] Tsunami deposits in Holocene sediments on Shita Plain, Shizuoka, central Japan
Keywords:Shita plain, Holocene, tsunami deposits
Geological coring in Hamatome lowland of the northern Shita plain, central Japan, revealed occurrence of two event deposits which composed of single or multiple graded beds with sharp erosional bases and 10–60-cm-thickness and represent the higher-energy hydrodynamic event. Radiocarbon dates show that two event deposits were deposited from AD 780 to AD 1025, and after AD1025, respectively. The lower event deposit overlies back marsh clay and in turn is overlain by backshore and beach ridge deposits, indicating that higher-energy hydrodynamic event was accompanied with rapid transgression. The correspondence between geological and historical records, we concluded that lower event deposit was caused by AD 887 Ninna tsunami and that the transgression was associated with submarine landslide and/or erosion by tsunami. The upper event deposit may be caused by AD 1498 Meio tsunami.