An analysis of the abundances and distributions of silt-sized heavy minerals from the U.S. mid-Atlantic outer continental shelf, slope, and rise shows that heavy minerals constitute a substantially greater weight percent of the silt fraction than that of the sand fraction regardless of environment and sediment texture. Concentrations of silt-sized heavy minerals progressively decrease from the shelf where they average 6.94%, to the slope and rise where they average 4.45% and 3.45%, respectively. A mixed amphibole-garnet+staurolite-epidote-pyroxene association dominates the silt-sized heavy mineral assemblage on the slope and rise; an ilmenite-amphibole-epidote association predominates on the shelf. Downslope trends in detrital nonmicaceous silt-sized heavy mineral abundances are related to hydraulic sorting rather than to chemical weathering. Elevated concentrations of the authigenic pyrite, siderite, dolomite+ankerite, and, possibly, phosphorite in the surficial slope sediment suggests that formation of silt-sized heavy minerals by diagenetic processes is relatively more important there than on the continental shelf or rise. ?? 1992.
Additional publication details
Mineralogy of the silt fraction in surficial sediments from the United States mid-Atlantic shelf, slope and rise