Carbonate slope morphology revealing sediment transfer from bank-to-slope (Little Bahama Bank, Bahamas)

International audienceNew high-quality multibeam and high-resolution seismic data reveal new observations on sedimenttransfer and distribution and margin morphometrics in the uppermost slope of Northeastern LittleBahama Bank between 20 and 300 m water depth. The echofacies/backscatter facies show an alongslopesediment distribution forming successive strips. The upper part of the uppermost slope corresponds tothe alternation of several submerged coral terraces and escarpments that could be related to LateQuaternary sea-level variations. The terraces could either be related to periods of stagnating sea-level orslow-down in sea-level change and therefore increased erosion by waves, or periods of accelerated sealevelrise since the Last Glacial Maximum. Terraces could therefore be related to coral construction anddrowing. The medium part corresponds to the marginal escarpment, a steep cemented area. The lowerpart of the uppermost slope shows a discontinuous Holocene sediment wedge with varying thicknessbetween 0 and 35 m. It is separated from the upper part by a zone of well-cemented seafloor associatedwith the marginal escarpment. Passing cold fronts result in sediment export caused by density cascading.The associated sediment fall-out and convective sedimentation can generate density currents that formthis wedge and eventually flow through linear structures on the upper slope. The survey reveals thepresence of recently active channels that extend over the entire uppermost slope and interrupt thewedge. The channels connect shallow tidal channels to submarine valleys connected to the proximal partof canyons. They directly feed the canyons with platform-derived sediment forming low-densityturbidity currents and could supply the deepest part of the system with coarse-grained sedimentdirectly exported from the carbonate platform