Acoustic evidences of along-slope processes associated with mass movement deposits on the Madeira Island lower slope (Eastern Central Atlantic).

Abstract

The Madeira Island lower slope has been build-up mostly by along slope-processes associated with mass movement deposits as seen in GEBCO bathymetry, multibeam bathymetry, Parasound echosounder profiles and multichannel seismic reflection profiles. A plastered contourite drift (Madeira Drift) developed on this lower slope, being composed of seismic units D1, D2 and D3. The most probable water mass responsible for its deposition is the Antarctica Bottom Water (AABW). The youngest sediments of seismic units D2 and D3 are affected by gravity-driven processes, probably slumps and debris flows, which moved downslope towards west. Parasound profiles show evidences of such mass movements on present-day seabottom (e.g. diffraction hyperbolae echoes) but also of past-events buried within the contourite sediments. These older debris flows are recognized by semitransparent/transparent acoustic facies and lenticular shape.