--> Abstract: Sedimentary Record of Longitudinal Transport in Late Pleistocene-Holocene of Bahamian Trough, by Paul D. Crevello; #90961 (1978).
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Abstract: Sedimentary Record of Longitudinal Transport in Late Pleistocene-Holocene of Bahamian Trough

Previous HitPaulTop D. Crevello

The upper 7 m of sediment in Exuma Sound shows a record of longitudinal transport by carbonate gravity flows. The basin, one of three intraplatform basins of the Great Bahama Bank, is 170 km along its axially dipping seafloor and 25 to 35 km wide between toe-of-slopes. With 48 closely spaced piston cores taken in conjunction with a detailed bathymetric and seismic reflection survey (3.5 kHz) in northern Exuma Sound, three gravity flows were mapped in a study area 45 by 75 km--two turbidites and one combination debris flow-turbidite. The turbidites are graded and/or laminated, grain-supported, skeletal calcarenites and calcilutites, whereas a composite sequence for the debris flow-turbidite is (a) a basal, poorly sorted, lithoclast gravel slurry (pebbly mudstone to muddy rudite) that grades abruptly into (b) a slightly graded, algal-plate, chalk-lithoclastic rudite and (c) parallel and/or cross-laminated, skeletal calcarenite and calcilutite.

Tracing one turbidite shows that it traveled 7 km onto the basin floor, then turned south down the axis for an additional 10 km. The seismic survey and isopach maps show that layers of gravel and sand, up to 1.5 m thick, which reach the basin axis, traveled 15 to 70 km from their platform-margin source. Sparse coring throughout the rest of the basin shows similar deposits and it seems likely that there is pervasive longitudinal transport from localized platform sources that rim the entire basin. From the cores in the study area it is estimated that 20% of the upper 7 m of sediment in Exuma Sound is deposited by sediment-gravity flows.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma