Abstract

Forty-five core-top samples taken in the Vema Channel (southwest Atlantic) within the deduced boundaries of two important bottom-currents have been analyzed for the particle size distribution of the noncarbonate silt-size fraction. This was done in order to characterize the sediment beneath each water-mass. Using statistical and graphical methods it was found that sediment beneath the high-velocity Antarctic Bottom Water in the bottom of the channel exhibits the coarsest mean size, poor sorting, and a large percent of coarse silt left as a lag deposit; sediment beneath the overlying low-velocity North Atlantic Deep Water is marked by fine mean size, good sorting, no coarse silt, and a large percent of fine silt; sediment beneath the intervening transition zone is characterized by finest mean size, moderate sorting, largest percent fine silt, and a small lag component of coarse silt. The methods developed for delineating bottom-currents in the Vema Channel may be applied to a wide range of benthic oceanographic settings as well as the geologic record in order to examine relative paleovelocity fluctuations of major bottom-currents.

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