Measurements of the sediment cover over mid-ocean ridges are potentially useful for tectonic
and volcanic problems because sediment thickness variations may reflect variations in
seafloor age. In profiler records recently collected with the deeply towed TOBI system,
however, we find that sediments on 0-2.5 Ma seafloor do not thicken systematically with
distance from the spreading axis as would be expected from increasing seafloor age. Average
sedimentation rates calculated from the thicknesses show some tendency to increase with
depth as found elsewhere on the Mid-Atlantic Ridge. Many of the deposits drape basement
topography and occur on outlying promontories, so sediment is probably deposited from
suspension in the bottom nepheloid layer rather than from turbidity currents or other gravity
flows. Enhanced sedimentation rates in deeper areas, therefore, occur because of enhanced
suspended load within the bottom nepheloid layer or reduced bottom movement which allow
particles to settle from suspension. The profiler records reveal a variation in the style of
sedimentation from draping and localised ponding on young seafloor, to accumulation in
large turbidite ponds farther off-axis, which probably reflects the progressive accumulation in
source areas and, due to sedimentation, progressively smoother pathways favourable to
turbidity currents.
Mitchell, N. C., S. Allerton and J. Escartin, Sedimentation on young ocean floor at the
Mid-Atlantic Ridge, 29 deg N,
Marine Geology, 148, 1-8, 1998.