Sedimentation on the Eastern United States Continental Slope

Along the continental margin of the eastern United States a major break in intercanyon continental slope sedimentation occurs at Cape Hatteras North of Cape Hatteras slope sediments are dominantly silts which exhibit little change in grain size from upper slope to lower slope Because of the Florida Current south of Cape Hatteras the upper slope has a greatly increased sand fraction compared to the north and grain size decreases downslope All slope sediments are high in mica relative to the inshore portions of the margin even the estuaries Slope sediments have an exotic authigenic heavy mineral suite containing iron carbonates and iron sulfides Detrital heavy minerals are depauperate in the densest fraction but otherwise mirror adjacent shelf suites Slope benthic foraminiferal suites are mixtures of shelf and slope forms Intercanyon portions of the slope are active depocenters North of Hatteras hemipelagic sedimentation is the dominant process with shelf spillover a secondary contributor South of the Cape spillover is much more important Although mass wasting phenomena have been shown in the literature on the grand scale there is little evidence for them in the upper six meters of sediment Clay mineralogy and mica distribution on the continental margin indicate that some sediment being carried by rivers is getting through the estuaries by passing the shelf and accumulating on the slope They further show that winnowing on the adjacent shelf both now and during the Holocene transgression has provided additional sediment to the slope system