Diatom assemblages in tsunami deposits in a paddy field and on paved roads from Ibaraki and Chiba Prefectures, Japan, generated by the 2011 Tohoku tsunami

Abstract

We visited Juo and Kashima (Ibaraki) and Hasunuma (Chiba) a few days after the 2011 earthquake off the Pacific coast of Tohoku. The tsunami left sandy deposits in paddy fields and on paved roads in the study sites, and the deposits comprise graded and laminated sandy sediments. Diatoms are abundant in the deposits and consist of mixed assemblages, including species with different environmental preferences. Diatom valves are better preserved than in modern tsunami deposits associated with the 1998 Papua New Guinea and the 1994 Java tsunamis, although some selective preservation is recognized due to the damage of species with fragile valves.