Geology and age model of the Lower Pleistocene Nojima, Ofuna, and Koshiba Formations of the middle Kazusa Group, a forearc basin-fill sequence on the Miura Peninsula, the Pacific side of central Japan

Island Arc ◽  
2014 ◽  
Vol 23 (2) ◽  
pp. 157-179 ◽  
Author(s):  
Atsushi Nozaki ◽  
Ryuichi Majima ◽  
Koji Kameo ◽  
Saburo Sakai ◽  
Atsuro Kouda ◽  
...  
Keyword(s):  
Forearc Basin ◽  
Central Japan ◽  
The Pacific ◽  
Pacific Side ◽  
Lower Pleistocene ◽  
Group A ◽  
Age Model ◽  
Basin Fill

Preferential formation of a slide plane in translational submarine landslide deposits in a Pleistocene forearc basin fill exposed in east-central Japan

2018 ◽  
Vol 477 (1) ◽  
pp. 241-253 ◽  
Author(s):  
Masayuki Utsunomiya ◽  
Atsushi Noda ◽  
Makoto Otsubo
Keyword(s):  
Pore Pressure ◽  
Slip Zone ◽  
Submarine Landslides ◽  
Forearc Basin ◽  
Central Japan ◽  
East Central ◽  
Preferential Formation ◽  
Lapilli Tuff ◽  
Tephra Beds ◽  
Basin Fill

AbstractTephra beds are considered to be potential failure planes for submarine landslides. Here, we report on an example of a coarse-ash/lapilli-tuff bed influencing translational slides. The studied mass-transport deposit (MTD) is intercalated in the Pleistocene forearc basin fill exposed in east-central Japan. This MTD consists of stacked siltstone blocks resulting from repeated imbricate thrusts branching from the décollement. The basal slide plane is located immediately below a pumice-rich coarse ash/lapilli-tuff bed. The material comprising the slip zone is injected into the overlying coarse-ash/lapilli-tuff bed, suggesting an upwards escape of excess porewater that resulted from elevated pore pressure. To explain this mode of occurrence, we propose that the detachment preferentially occurred at the top and base of the coarse-ash-tuff-rich interval which appears to have been stronger relative to the adjacent silt-dominated interval. The pumiceous coarse-ash and lapilli-tuff bed behaved as a rigid plate on top of the high-pore-pressure slip zone, which sustained the translational slide on the gentle continental slope. Therefore, in translational submarine landslides, the preferential formation of a slide plane is caused by differing frictional resistances in the layered sediments.

scholarly journals A shell-concentrated sandstone bed containing vesicomyid shells from the Lower Pleistocene Nojima Formation, Kazusa Group, Pacific side of central Japan

2014 ◽  
Vol 120 (7) ◽  
pp. 221-231 ◽  
Author(s):  
Masayuki Utsunomiya ◽  
Chihiro Nagahama ◽  
Robert G. Jenkins ◽  
Atsushi Nozaki ◽  
Ryuichi Majima
Keyword(s):  
Central Japan ◽  
Pacific Side ◽  
Lower Pleistocene
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