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Origin of shallow submarine mass movements and their glide planes—Sedimentological and geotechnical analyses from the continental slope off northern Norway
Author(s) -
Baeten Nicole J.,
Laberg Jan Sverre,
Vanneste Maarten,
Forsberg Carl Fredrik,
Kvalstad Tore J.,
Forwick Matthias,
Vorren Tore O.,
Haflidason Haflidi
Publication year - 2014
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2013jf003068
Subject(s) - geology , submarine landslide , mass movement , geomorphology , landslide , submarine , debris , shear (geology) , pore water pressure , continental shelf , seismology , geotechnical engineering , petrology , oceanography
Submarine landslides are often characterized by a basal surface of rupture parallel to the stratigraphy, in which downslope movement is initiated. However, little is known about the sedimentology and physical properties of the sediments within these surfaces. In this study, we present a multiproxy analysis of the sediments collected from a giant piston core penetrating a shallow submarine mass transport deposit, in combination with high‐resolution seismoacoustic data to identify and characterize the basal glide plane and the weaker sediments in which movement was initiated. The initial phase of instability consists of a single fracture that formed due to the downslope movement of a mostly intact slab of sediments. The 16 m long core, comprising mostly undisturbed massive and laminated ice‐rafted debris‐rich clay penetrated this slab. The base of the slab is characterized by a high‐amplitude semicontinuous reflection visible on the subbottom profiler data at about 12.5 m depth, interpreted to originate from the glide plane on top of a plumite deposit. This plumite has dilative behavior with pore pressure decrease with increasing shear strain and high undrained shear strength. Movement probably started within contouritic sediments immediately above the glide plane, characterized by higher sensitivities and higher water contents. The occurrence of the mass movements documented in this study are likely affected by the presence of a submarine landslide complex directly downslope. The slide scar of this landslide complex promoted retrogressive movement farther upslope and progressive spreading of strain softening along the slide base and in the slide mass. Numerical models (infinite slope, BING, and retrogressive slope models) illustrate that the present‐day continental slope is essentially stable and allow reconstruction of the failure processes when initiated by an external trigger.