Deposition and preservation of fine-grained turbidites around the Japanese islands

Ken IKEHARA; Kazuko USAMI; Naohisa NISHIDA

Presentation information

Oral

Symbol H (Human Geosciences) » H-CG Complex & General

[H-CG37_30PM2] Interdisciplinary approach to earth's changing surface

Wed. Apr 30, 2014 4:15 PM - 5:30 PM 421 (4F)

Convener:*Naofumi Yamaguchi(Center for Water Environment Studies, Ibaraki University), Hajime Naruse(Department of Geology and Mineralogy, Graduate School of Science, Kyoto University), Shigehiro Fujino(Faculty of Life and Environmental Sciences, University of Tsukuba), Koji Seike(Atmosphere and Ocean Research Institute, University of Tokyo), Chair:Naofumi Yamaguchi(Center for Water Environment Studies, Ibaraki University)

5:00 PM - 5:15 PM

[HCG37-11] Deposition and preservation of fine-grained turbidites around the Japanese islands

*Ken IKEHARA¹, Kazuko USAMI¹, Naohisa NISHIDA¹ (1.Geological Survey of Japan, AIST)

Keywords:turbidite, earthquake, tsunami, preservation potential, sedimentary structure, depositional process

We will report the sedimentological characteristics of fine-grained turbidites occurred around the Japanese islands such as off Sanriku, off Kumano, Suraga Bay, Beppu Bay, Japan Trench and off Hidaka. Some of these are thought to be formed in relation to the slope failures by the earthquake-ground shaking. Sometimes, subaqueous debris flow deposits were observed below the fine-grained turbidites. Agitation of the shelf floor by the tsunami waves is another mechanism to create the fine-grained turbidites. Third mechanism is the hyperpycnal flows related to the flood events. Preservation potential of the fine-grained turbidites will be discussed based on the repeated surveys of surface sediments off Sanriku region after the 2011 Tohoku-oki earthquake and its related tsunami. Based on these observation, we will discuss on the depositional processes of the fine-grained turbidites and preferable setting to preserve them as the geological records.