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Process, time and architecture: lessons from slope contourites and their failures in the path of the Labrador Current
Piper, D.J.W. (2014). Process, time and architecture: lessons from slope contourites and their failures in the path of the Labrador Current, in: Van Rooij, D. et al. (Ed.) Book of Abstracts. 2nd Deep-Water Circulation Congress: The Contourite Log-book. Ghent, Belgium, 10-12 September 2014. VLIZ Special Publication, 69: pp. 3-4
In: Van Rooij, D.; Rüggeberg, A. (Ed.) (2014). Book of Abstracts. 2nd Deep-Water Circulation Congress: The Contourite Log-book. Ghent, Belgium, 10-12 September 2014. VLIZ Special Publication, 69. Ghent University, Department of Geology and Soil Science/Flanders Marine Institute (VLIZ): Oostende. xviii, 152 pp., more
In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more

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Keywords
    Liquefaction; Marine
Author keywords
    Drift architecture; Current strength; Spreading failure; Earthquake trigger

Author  Top 
  • Piper, D.J.W.

Abstract
    The southeastern Canadian continental slope is swept by the powerful Labrador Current. Over the past glacial cycle, changes in ocean circulation, meltwater supply, and glacial ice extent produced strong changes in current strength and pathways which are reflected in sediment drift architecture. Previous studies show that failure of sediment on steep (>3°), canyoned slopes off eastern Canada recurs every ~10-30 ka and are likely related to earthquakes. On gently dipping (1–1.5°) flanks of drifts in Flemish Pass, Atterberg limits show that some silty winnowed sediment is susceptible to liquefaction by cyclic loading. Here, failures occur every ~10-30 ka as on steeper slopes, followed by ~200–400 ka periods of stability and sediment accumulation. Build up of pore pressure from migrating sub-surface gas and fluids then allows earthquake-triggered failure on such low slopes. The style of failure is mostly lateral spreading with partly retrogressive failure upslope. Sediment drifts respond in a complex manner to changes in current flow on at least millennial and longer time scales, with resulting spatial variation in sediment type. Failure preconditioning on low slopes requires winnowed silty sediment capable of liquefaction and less permeable muddier plume sediment that allow build up of gas, followed by triggering by M>7 earthquakes.

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