SILT HEAVY-MINERAL DISTRIBUTIONS OFF THE SOUTHEASTERN UNITED-STATES

Until recently heavy-mineral studies of marine sediments were largely restricted to sand fractions. New techniques permitting analysis of de calcified silt fractions have been applied to sediments off the southe astern United States. Our data, which confirm predictions from the bas ic relationship among grain size, specific gravity, and equivalent hyd raulic transport behavior, show that concentrations and average diamet ers of the silt heavy minerals progressively decrease seaward. Heavy m inerals always constitute a substantially greater weight percent of th e silt than of the sand fraction. Despite corroded surface textures su ggestive of extensive weathering and dissolution, spatial trends in th e detrital heavy-mineral populations are predominantly controlled by s ource and hydraulic factors.