Links Between Morphology and Geotechnical Characteristics of Large Debris Flow Deposits in the Albatross Area on the Scotian Slope (SE Canada)

Abstract

Links between morphology and geotechnical characteristics of large debris flow deposits in the albatross area on the Scotian slope (SE Canada) A succession of debris flow deposits are recognized in the Albatross area of the Scotian Slope (SE Canada). A geotechnical study has been conducted on samples recovered in 28 piston cores. Results show that sediment of the area can be separated into four geotechnical groups according to consolidation state. These groups are strongly related to the nature of the deposits. All the cores sampled in the proximal part of the debris flow deposits show overconsolidated blocks included in a normally consolidated matrix. The thickness of initial failures is estimated as 30–56 m based on the peak value of undrained shear strength measured on debris flow deposits. Simple viscous analysis of the most recent debris flow allows an estimate of postdepositional erosion at the location where debris flows have been channeled. The calculated maximum value of 80 m is consistent with results from seismic reflection profiling, but the relationship of this erosion with the debris flow motion remains uncertain. Stratigraphically equivalent debris flows 50 km west in the Verrill Canyon area transformed into turbidity currents. Whether such a transformation is due to the initial pore pressure conditions related to shallow gas or to earthquake accelerations, high pore pressure is generated and leads to grain buoyancy and a high entrainment rate. Ignitive turbidity currents generated on low slope are probably earthquake triggered and associated with shallow gas.