Rosenstiel School of Marine and Atmospheric Sciences, United States

Core, logging, and seismic data of ODP Leg 166 were used to analyse the Miocene and Lower Pliocene Bahamian outer carbonate ramp. Sediments consist of an alternation of light-gray and dark-gray wackestones/packstones with intercalations of turbidite packages. Light-gray wackestones/packstones record phases of export of shallow water components whereas the ramp did not export material during deposition of the dark-gray layers which contain up to 20% clay. The calciturbidites are arranged into mounded lobate bodies with feeder channels. Some of the lobe systems are coalescent, others are laterally disconnected thus indicating feeding by line sources. Turbidite packages of the outer ramp were deposited during sea-level highstands and lowstands. Highstand turbidites contain shallow-water carbonate particles such as green algal debris and epiphytic foraminifera whereas lowstand turbidites are dominated by abraded bioclasts. Within individual depositional sequences, lowstand turbidites are in a more basinward position than highstand turbidites. Depocenters of gravity flows change from an Early and Middle Miocene outer ramp position to a Late Miocene and Early Pliocene basin floor position. This evolution is triggered by the strengthening of the bottom current system in the Santaren Channel and the Straits of Florida.