DEPOSITIONAL FLUXES, PALAEOPRODUCTIVITY, AND ICE RAFTING IN THE NE ATLANTIC OVER THE PAST 30 KA

Over the last 30 ka, sediment flux to the northeast Atlantic Ocean has been strongly influenced by the growth and decay of northern hemisphe re ice sheets, input of ice-rafted detritus, the migration of the pola r front, and associated changes in patterns of biological productivity . We examined cores from 47 degrees N to 60 degrees N along 20 degrees W to determine the flux of components including carbonate, organic ca rbon and terrigenous material and divided into size fractions. During the glacial period, fine carbonate flux was low and ice-rafted input h igh. Burial flux during the Holocene became dominated by coccolith and foraminiferal carbonate, with minor organic matter and biogenic silic a. Estimates of palaeoproductivity are ambiguous: a method which corre cts for water depth and sedimentation rate suggests no clear glacial t o Holocene change, whereas a method based on percentage of organic car bon suggests increased productivity from glacial to Holocene of around 60%. Sites of sediment focusing saw a change from enhanced fine terri genous flux in the glacial to enhanced fine carbonate in the Holocene. After compensating for sediment focusing, glacial ice-rafted flux dis tribution shows a decrease from south to north across the area, reflec ting cyclonic surface water circulation. Deposition of ice-rafted detr itus during Heinrich events H1 and H2 led to enhanced preservation of organic matter immediately beneath the layers, indicating a rapid accu mulation rate.