Submarine landslides and mass-transport deposition in the Nankai fore-arc

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Author(s): Strasser, M.; Henry, P.; Kanamatsu, Toshiya; Moe, K.; Moore, G. F.
Integrated Ocean Drilling Program, Expedition 333 Scientists
Author Affiliation(s): Primary:
Eidgenössische Technische Hochshcule Zürich, Geological Institute, Zurich, Switzerland
Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, France
Japan Agency for Marine-Earth Science and Technology, Japan
University of Hawaii at Manoa, United States
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Multiple lines of evidence exist for a range of sediment mass movement processes within the shallow megasplay fault zone (MSFZ) area and the adjacent slope basin in the outer fore-arc of the Nankai subduction zone, Japan. Diagnostic features observed in 3-D reflection seismic data and in cores from Integrated Ocean Drilling Program (IODP) Expedition 316 document a complex mass movement history spanning at least ∼2.87 million years. Various modes and scales of sediment remobilization can be related to the different morphotectonic settings in which they occurred and allow integration of knowledge on the spatial and temporal distribution of submarine landslides into a holistic reconstruction of the tectonostratigraphic evolution. New data from the most-recent Nankai IODP Expedition 333, which drilled and cored a Pleistocene-to-Holocene succession of the slope-basin seaward of the MSFZ, provides unprecedented details on submarine landslide processes occurring over the last Million year. The slope-basin represents the depocentre for downslope sediment transport and is characterized in 3-D reflection seismic data by several mass-transport deposits (MTDs), including an up to 180 m thick MTD. Here we present D/V Chikyu shipboard results and first post cruise results from Site C0018, including litho-bio- magneto-tephra- and stable isotope-stratigraphy, X-ray computed tomography analysis and physical properties data. Six MTDs were identified from visual core description and X-ray CT-scans. The thickest MTD is also the oldest (emplaced between 0.85 and 1.05 Ma) and it coincides with a lithological transition between a sandy turbidite sequence below, and ash-bearing hemipelagites comprising several MTDs above. Deformation styles within the MTD are heterogeneous: intervals of disturbed sediments are interbedded within intervals inferred to retain original, coherent bedding. In three occurrences the base of the MTD is defined by a shear zone within fine-grained sediments. These observations suggest that slumping and mass-transport is dominated by localized plastic deformation. Other MTDs are related to basal granular volcaniclastic deposits, suggesting earthquake-induced liquefaction as failure mechanism. However, the temporal distribution of observed landslides suggests submarine slope destabilization does not occur systematically during subduction zone earthquakes. This implies that pre-conditioning factors such as sedimentation, tectonic oversteepening and/or lateral transmission of fluids overpressure may exert the key role in controlling the temporal and spatial occurrence of submarine landslides. Nevertheless, mass movements are an active process that is shaping the present-day seafloor, as evidenced by numerous slump scars in bathymetry data and the occurrence of a shallow, presumably Holocene, MTD at Site C0018.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Bathymetry; Cenozoic; Continental slope; Cores; Deformation; Expedition 316; Expedition 333; Failures; Faults; Fine-grained materials; Geophysical methods; IODP Site C0018; Integrated Ocean Drilling Program; Interpretation; Liquefaction; Marine environment; Mass movements; Mechanism; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Plastic deformation; Quaternary; Sediment transport; Sediments; Seismic methods; Seismicity; Shear zones; Slumping; Subduction zones; Submarine environment; Three-dimensional models; Transport; Volcaniclastics; West Pacific
Coordinates: N330925 N330925 E1364053 E1364053
Record ID: 2015099609
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