Clay mineral signature of the NW Atlantic Boundary Undercurrent

Abstract

Surface sediments were sampled along 2 transects, across the Iceland and Irminger basins and in the Labrador Sea. Clay mineral assemblages (deduced from X-ray analyses of the carbonate-free < 2 μm fraction) are largely dominated by smectites (about 60%) in the Iceland and Irminger basins. In the Labrador Sea, smectites are present along the Greenland Slope, but absent or rare in sediments from the Labrador Slope. They may, however, represent up to 50% of the clay fraction at depths between 2800 and 3400 m along both margins of the Labrador Sea, i.e., along the axis of the Western Boundary Undercurrent (WBUC). A detrital supply from the adjacent continents is unlikely. The WBUC is thought to be responsible for erosion and transport of fine particles from the smectite-rich Irminger and Iceland Basins, then for their redeposition in the Labrador Sea. These results suggest that clay minerals can be used as paleocurrent indicators in the Northwest Atlantic.