Late Quaternary sediment, sediment mass flow processes and slope stability on the Scotian Slope, Canada

Authors

  • DAVID C. MOSHER,

    1. Atlantic Geoscience Centre, Bedford Institute of Oceanography, PO 1006 Dartmouth, Nova Scotia, Canada B2Y 4A2
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      Pacific Geoscience Centre, PO Box 6000, 9860 west Saanich Rd, Sidney, British Columbia, Canada V8L 4B2.

  • KATHRYN MORAN,

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      Pacific Geoscience Centre, PO Box 6000, 9860 west Saanich Rd, Sidney, British Columbia, Canada V8L 4B2.

  • RICHARD N. HISCOTT

    1. Department of Earth Science, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1V 3X5
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ABSTRACT

The study area, just to the west of the Verrill Canyon on the Scotian Slope, eastern Canada, exhibits both large and small scale sediment mass movement features. Study of high resolution seismic reflection and sidescan sonar data shows that a large portion (approximately 70%) of the near surface sediment (<20 m) in the area has undergone erosion, rotational slumping and internal deformation. Remoulded sediment observed in physical properties profiles of piston cores and sediment deformation structures are further evidence of slumping. Small scale mass flow events are recorded by abundant turbidites and debris flow deposits noted in piston cores. Sediment physical properties are highly dependent on sediment type (lithofacies). Frequent facies changes, both temporally and spatially, make correlation between cores difficult.

Although the small scale mass movement events correlate with glacial recession on the continental shelf and lower relative sea levels, the triggering mechanisms for the large scale events are less obvious. Slope stability analyses indicate that, at present, the seabed is stable. The most plausible explanation for large scale slope failures in this region are ground accelerations related to earthquake shock. Our analyses demonstrate that it is unlikely that large magnitude, distant earthquakes, such as those previously proposed in the Laurentian Slope Seismic Zone (LSP) model, could initiate failure of sediment in the study region. Our data support the interpretation that more frequent, lower magnitude earthquakes, closer to the study region, as previously proposed in the Eastern Slope Experimental Source Zone (ESX) model, are the likely causes of large scale slope failures. Furthermore, excess pore pressures resulting from shallow gas and/or high sedimentation rates during deglaciation contribute to slope failure.

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