In search of paleotsunami deposits in Himi city, Toyama prefecture

Abstract

Sedimentological study was carried out in order to clarify the paleotsunami history in the northern Hokuriku region. Facies analysis for short core samples collected from the lowland behind a beach ridge in Shimao, Himi city, Toyama prefecture determine that the lowland beds consist of sediments from a beach ridge, a marsh, a pond and a swamp, and identify six event deposits in these sediments. Two of these event deposits or wood fragments rich layers were found in the almost same depth below the ground level, setting these two event deposits as an event bed. The observed ¹⁴C age below this event bed is 2,344-2,155 cal BP. The mineralogical and sedimentological characteristics as well as spatial distribution of the observed event bed suggest that it may have been originated from a tsunami. However, the possibility of a river flooding event cannot be excluded, and therefore further study is needed to clarify the origin of it.