Sedimentological and micropaleontological characteristics of tsunami deposits associated with the 2024 Noto Peninsula earthquake

This study reports sedimentological and paleontological features of deposits left by the 2024 Noto Peninsula tsunami in Suzu City, Japan. Tsunami deposits were found up to 70 m inland from the post-tsunami shoreline along our transect. The tsunami deposits were collected at five locations for observation by Soft X-ray and CT images, grain-size analysis, and diatom analysis. Soft X-ray and CT images identified that the five stratigraphic units (Units 1–5) at the most seaward location (SZ1) and deposits with faint laminae at the other locations (SZ2–4). Grain-size analysis showed that the tsunami deposits generally composed of fine to very fine sand at all sampled locations. At SZ1, Unit 3 exhibits climbing ripples with their leeside seaward. The ripple tops were probably dragged seaward. The eroded upper contact of Unit 4 implies yet another current at SZ1. Diatom assemblages within the tsunami deposits are dominated by marine and brackish species, except Unit 4 at SZ1 with more than 30% freshwater terrestrial species. Diatom assemblages in the tsunami deposits, vented sediments, and beach sand suggest that the SZ1 tsunami deposit was derived from both terrestrial and marine sources, while the main source was the coastal beach at the other locations.