Bottom roughness of the Mid-Atlantic Ridge flank observed in SeaMARC II sidescan sonar and sea beam multibeam bathymetry.

Abstract

Existing sea beam bathymetry along the Mid-Atlantic Ridge (MAR) axis, and SeaMARC II sidescan-sonar images along Kane Fracture Zone, have been analyzed to characterize patterns of bottom roughness that may be expected in the ONR acoustic reverberation corridor. Fault patterns along the MAR axis were determined in slope maps calculated from gridded beam-point data, and along Kane Fracture Zone they were mapped from sidescan-sonar images geometrically corrected for seafloor depth variations. Faults occur primarily in three orientations within well-defined provinces. MAR-parallel faults are restricted to the interior of MAR spreading segments, dip toward the spreading axis, and commonly have large throw (≳100’s m) and steep dips (up to 50°). Smaller, oblique to curvilinear faults occur at boundaries between spreading segments. MAR-orthogonal faults are restricted to fracture-valley crust generated in the large-offset Kane Transform Zone. Hummocky volcanic edifices and volcanic cones appear intermittently within spreading segments.