4th International Submarine Canyon Symposium (INCISE2018)

5-7 November 2018, Shenzhen, CHINA

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This is the detail of Repeated deposition of thick muddy turbidites and mass-transport deposits in small basins along the Japan Trench floor

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Author
Ken Ikehara
Co-Author(s)
Toshiya Kanamatsu, Kazuko Usami, Arata Kioka and Michael Strasser
Abstarct Title
Repeated deposition of thick muddy turbidites and mass-transport deposits in small basins along the Japan Trench floor
Abstarct Body
Japan Trench is a plate boundary between the Pacific and Okhotsk Plates with its convergent rate of 8.0¬¬–8.6 cm/y. Horst-graben bathymetric relief on the obliquely subducting Pacific Plate makes a series of small basins along the trench floor. In each small basin, some thick acoustically transparent layers are found in the sub-bottom profiling records. Collected cores from the basins contained thick muddy turbidite beds. At the central Japan Trench where no apparent submarine canyon occurs in the lower slope, the thick muddy turbidites were correlated to onshore tsunami deposits on Sendai Plain, and considered as earthquake-induced turbidites. Differences of radiocarbon ages between hemipelagic and turbidite mud suggested the surface sediment remobilization by the huge earthquakes for the origin of turbidity currents. On the other hand, apparent submarine canyon is found at the northern and southern ends of the trench. At the southern end, the thickest muddy turbidite was obtained. Submarine canyon may play important role to transport the fine materials. A thick homogeneous mud (MTD) occurred at the northernmost basin. The MTD contained well-preserved calcareous benthic foraminifers which were lived in the outer shelf to the upper slope. There are several submarine landslide bodies in the upper slope of the Hidaka Trough. Submarine landslides in the upper slope may provide a significant amount of mud to the ultra-deep trench floor.
INCISE Theme
Special Session: Canyons and trenches in the South China Sea and West Pacific
Presentation Type
Oral Presentation
Keywords
Japan Trench, homogeneous mud, benthic foraminifer, slope failure

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