Compositional changes in particulate matter on the Iceland Rise, through the water column, and at the seafloor

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Abstract
Local resuspension of sediments along the Iceland Rise was substantiated by the collection in sediment traps of large particles whose source is clearly the seafloor. These resuspended components included benthic foraminifera, iron-oxide coated planktonic foraminifera, the glacial, subpolar assemblage planktonic foraminifera (Neogloboquadring pachyderma (sinistral)), and an increase in the volcanic glass and mineral grain/aggregate component with proximity to the seafloor. The horizontal flux of particulate matter in the near-bottom nepheloid layer through the region was .simeq. 200 kg/s. The apparent ventrical flux of sediment calculated from sediment traps at 500 m above bottom (mab) was an order of magnitude less than Recent sediment accumulation rates, suggesting a larger fraction of the sediments in the region was brought in horizontally via button currents or turbidity currents. The compositional changes with depth in the material collected in the sediment traps indicated that most of the changes in the material due to dissolution, degradation, and decomposition occurred while the material resided on the seafloor or during periods of resuspension rather than during transit through the water column. Regional variations in clay mineralogy, organic carbon and carbonate content indicated preferential preservation in cores from a channel in the study region or preferential decomposition, dissolution, and/or erosion of the surface sediments beneath the bottom current.