Near-surface geology and sediment-failure geohazards of the central Scotian Slope

Abstract

The central Scotian Slope demonstrates a complex seafloor morphology superimposed on a regional gradient of 24 across the margin. The west-central Scotian Slope is characterized by a relatively smooth seafloor, but with numerous 1080-m (33260-ft)-high escarpments representing slide failure scars. In the east, the seafloor is highly dissected by canyons. Throughout the region are scars and deposits of sediment mass failures, including retrogressive headwalls, rotational slumps, slides, creep, debris-flow deposits, and turbidites.The complexity of failure styles and triggering mechanisms identified underscores the need for comprehensive site assessments for situating seabed facilities. Critical factors that need to be taken into account include local terrain analysis and shallow subbottom stratigraphy. Slope-stability analysis has shown the surface sediment to be statically stable, except on steep escarpments and canyon walls. There is evidence, however, of sediment failures that approximately correlate to glacial advances (2512, 75, and 130 ka), providing some clue as to potential triggering mechanisms. Sparse, passive-margin, tectonic earthquakes, however, are the likely cause for large-scale, regionally correlated failures and failure escarpments.