Seismic Sedimentologic Interpretation of a Carbonate Slope, North Margin of Little Bahama Bank: ABSTRACT

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Analyses of seismic profiles and descriptions of sediments from ODP Leg 101 cores were combined to investigate the evolution of the northern margin of Little Bahama Bank, which has been prograding northward since the early Mio­ cene. Modern depositional systems on the midslope and lower slope are found to be uncharacteristic of interpreted an­ cient sedimentary environments. Large slump masses covered much of the lower slope during the middle Miocene, pos­ sibly triggered by a regional tectonic event. Throughout the late Miocene and most of the Pliocene, a channel and levee system meandered across the sediment apron of the lower slope. The modern lower slope contains no meandering chan­ nels, although gullies incised in the midslope funnel sediments to the base-of-slope apron, actively promoting sediment bypass on an accretionary margin. These changes in sedimentation pattern on the lower slope indicate increasing strength of ocean-bottom contour-following currents from the Pliocene. Pliocene to Holocene gravitational creep has produced large-scale rotational movement of unlithified sediments and a major detachment surface along the base of the middle Miocene slump masses. These creep lobes extend far into the lower slope, where sediments are contorted by propagation of, and movement along, multiple minor detachment surfaces.