ACCELERATOR MASS-SPECTROMETRY RADIOCARBON STRATIGRAPHIES IN DEEP LABRADOR SEA CORES - PALEOCEANOGRAPHIC IMPLICATIONS

Foraminiferal accelerator mass spectrometry (AMS) C-14 ages and benthi c-planktonic age differences in surface-layer sediments of Labrador Se a are influenced by bioturbation and by changes in the relative abunda nce of foraminiferal species carrying the C-14 signal. Using benthic-m ixing models we demonstrate that inverse benthic-planktonic age differ ences can be generated when the effect of benthic mixing and abundance change exceeds apparent age differences between surface water and dee p water. AMS C-14 ages obtained put constraints on the timing of major paleoceanographic changes in the basin, notably on the history of the Western Boundary Undercurrent, which was clearly reinitiated during t he mid-deglaciation and intensified during the last 2-3 ka.