[H-QR05] Natural hazard and human activity recorded in underwater geoarchaeological structure

[HQR05-P02] Characteristics and its significance of marine cores collected from inner Uranouchi Bay, Kochi Prefecture

*Masafumi MURAYAMA¹, Wataru Tanikawa², Akira Ijiri², Tatsuhiko Hoshino², Takehiro Hirose², Toshiya Fujiwara², Kazuya Kitada², Kastuya Nejigaki³, Tokuyama Hidekazu⁴, Go-Ichiro Uramoto⁴, Kazuno Arai⁴, Kondo Yasuo³, Yuhji Yamamoto⁴, Research Member Kurodagoori⁴ (1.Faculty of Agriculture and Marine Science, Kochi University, 2.JAMSTEC, 3.Graduate School of Integrated Arts and Sciences, Kochi University, 4.Center for Advanced Marine Core Research, Kochi University)

Keywords:Kuroda-Gori archeological survey, Uranouchi Bay, Event Sediments

For the purpose of the Kuroda-Gori archeological survey, sediment cores collected from the inner part (10m depth) of Uranouchi Bay, Kochi Prefecture, were analyzed. The history of changes in the marine environment and biota at that time was also restored. Uranouchi Bay, located in the central part of Tosa Bay, Kochi Prefecture, faces the north side of the Yokonami Peninsula, is elongated in the east and west, and is known as a sinking bay with a depth of 12 km. A 4-m sediment core was collected by vibro coring using the Kochi University research vessel "Nechun". Since the sampling point was not affected by the surrounding river, this core sample is considered to have recorded detailed environmental changes in the bay. The collected core samples were subjected to X-ray CT and MSCL analysis, and then halved to describe the naked eye and to collect and identify frequently occurring shellfish. The lithology of the sediment is olive-colored sity clay, which generally contains many shell pieces. The area near the upper part of the core was dark and had a strong hydrogen sulfide odor. In addition, event deposits with well-developed grains are observed in the lower part of the core, and the origin of the deposits will be examined in the future.