The southwest Florida continental slope, bordering the northern Straits of Florida, consists of a thick accumulation of carbonate sediments. High-resolution seismic data show oblique prograding clinoforms oriented offbank indicating large amounts of shelf-derived material are being transported off the shelf and deposited on the slope. No evidence of mass wasting was found, suggesting deposition occurred by a continuous influx from the adjacent shelf.
Sediment cores show an upward gradation from medium to coarse carbonate sands and granules to fine muds. The sand and granule fraction, dominated by coralline algae, mollusks, and benthic foraminifera, is typical of sediments found on the adjacent shelf. The fine fraction, however, is a foram or pteropod ooze containing only minor amounts of shelf-derived material.
The fining-upward sequence indicated the greatest input of shelf material occurred during lowered sea level. During these periods, large quantities of shelf sediments were funneled through breaks in the shallow banks to the north and deposited on the slope. As sea level continued to rise, less shelf sediment was transported offbank. Under current conditions of high sea level, very little shelf material is being contributed to the slope.
The slope therefore acts as a sink during sea level lowstands, for shelf-derived carbonate material produced during sea level highstands. The existence of at least 5 such sequences implies a cyclicity of similar depositional episodes that may be correlated with sea level fluctuations.