Sedimentological effects of strong southward flow in the Straits of Florida

Periodic southerly currents along the western side of the Straits of Florida are sufficiently strong to erode the seafloor and create large sand waves and coral mounds up to several meters high. Mapping with side-looking sonar and visual observations from the Nuclear Research Submarine NR-1 show that the sand waves are confined to an area about 2 km wide, but over 70 km long. Southerly currents in excess of 50 cm s-1 were measured during our dives, and the size of the bedforms and grain size of sediments suggests currents could attain velocities of 100 cm s-1. The eastern boundary of the sand waves terminates abruptly with an erosional cliff or a series of erosional steps, grades to a zone of nondeposition and then to an area of sediment accumulation. In the central Straits are regions of ripples, megaripples and small coral mounds that indicate persistent flow to the north. Chemical as well as current erosion appears to be altering the seafloor on the southern side of the Northwest Providence Channel, which feeds into the Straits of Florida. Relict lithoherms are abundant in this channel, but they are much smaller than those observed further north in the Straits of Florida. Bedforms and current measurements show a strong northwest flow in the channel along the south wall. ?? 1989.