Variability of clay-mineral composition on Carolina Slope (NW Atlantic) during marine isotope stages 1–3 and its paleoceanographic significance

Abstract

The clay-mineral composition of marine isotope stages 1–3 sediments at the Ocean Drilling program (ODP) Site 1055 on the Carolina Slope consists mainly of illite, kaolinite, chlorite and smectite. Clay-mineral variability is marked by a distinct increase in the relative amounts of kaolinite and smectite during the Holocene and by high illite and to a lesser extent chlorite relative amounts during marine isotopic stages 2 and 3. This grouping of clay minerals as two different assemblages during different isotopic stages suggest their different source affinities. The increase in the ‘kaolinite+smectite’ assemblage in the Holocene is accompanied by a significant increase in the sedimentation rate. The change in the sedimentation regime after the Last Glacial Maximum is interpreted to be related to resuspension and advection of clays and silts by increased deep water activity over the Bermuda Rise, followed by their transport to Site 1055 on the Carolina Slope by shallow elements of the North Atlantic Deep Water. High amplitude variations with high illite amounts characterize marine isotope stage 3 and appear to be related to Heinrich events.