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Seismic facies analyses of more than 1,200 km of high-resolution air-gun seismic reflection profiles, combined with sedimentologic data from 150 bottom samples, and observations from submersibles, have resulted in correlation of reflection patterns with sedimentary facies for various off-platform carbonate environments in the northern Bahamas. Divergent to oblique progradational reflection patterns have been recorded from large (100 km × 50 km × 600 m) carbonate-sediment drifts of well-sorted fine sands off the northwest corners of both Little (LBB) and Great Bahama Bank (GBB). These drifts have been constructed since the middle Miocene by contour-following near-bottom flow of the Florida Current with velocities of up to 50 cm/sec and greater. Discontinuous subb ttom reflections were observed at the base of the slope south of LBB and were found to correlate with proximal turbidites. An even, parallel, continuous subbottom reflection pattern is typical of basinal areas of pelagic oozes, deposited uniformly over wide areas, interbedded with thin, distal turbidites.
Large-scale (1 to 5 km across) mounded, chaotic to contorted-discordant reflection patterns were observed predominately on the upper slope south of LBB and appear to be indicative of large slumps. Smaller scale (less than 0.5 km across), mounded, chaotic reflection patterns, however, were found to correlate with in-situ constructional deep-water bioherms (lithoherms) found at the base of the slope west of LBB. Chaotic reflection patterns are common on upper slopes and are interpreted as a highly variable sediment gravity-flow and slump facies. Lenses of wavy, subparallel, chaotic reflectors found on the slope north of GBB are interpreted as channelized debris-flow deposits.
Recognition of similar reflection patterns from ancient off-platform limestone sequences may be useful in the seismic stratigraphic interpretations of paleo-environments and lithofacies.
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