SEDIMENT SUPPLY TO THE SE BAFFIN SLOPE AND NORTHWEST LABRADOR SEA DURING THE LAST GLACIAL CYCLE

The interaction between the sediment dynamics and iceberg rafting by the Hudson Strait ice stream of the Laurentide Ice Sheet (LIS) is poorly understood. Recent publications by Dalton et al. and Pico et al. suggested a significant reduction of the LIS during MIS 3, implying either a significant retreat or absence of the Hudson Strait ice stream. Here we report data from three sediment cores, namely Hu97048-07 (62.67°N; 60.57°W; 938 m water depth), Hu92045-04 (59.81°N; 58.13°W; 2761 m water depth), and Hu92045-05 (59.81°N; 56.46°W; 2932 m water depth) retrieved from the SE Baffin Slope and lower slope off Hudson Strait in the deep Labrador Sea. The 88-ka reference core on the SE Baffin Slope was investigated with new oxygen isotope stratigraphy, XRF geochemistry, and 16 ¹⁴C data. This record is correlated to 13 regional cores providing a paleoceanographic and sediment source record over the last 40 ka from the shelf to the basin floor. This section overlies a 3-m-thick blocky mass-transport deposit, likely of MIS 4 slope sediment, which overlies 77–88 ka autochthonous sediment. Detrital carbonate-rich (DC) sediment layers H0-H4, based on bulk geochemistry, were derived from Hudson Strait. Shortly after H2 and H3, the shelf-crossing Cumberland Sound ice stream supplied dark brown ice-proximal stratified sediments but no glacigenic debris flow deposits. A minor supply of carbonate-rich sediment from Baffin Bay is recognized in the geochemistry data, allowing chronologic integration of the Baffin Bay detrital carbonate (BBDC) and the Labrador Sea DC records and implying an open seaway through the Davis Strait. The deep-water counterparts of H3, H4, and H5 events in the deep Labrador basin exhibit variable thickness, ranging from 4 to 10 m thick units of nepheloid-flow deposits and thin-bedded carbonate-rich mud turbidites derived from glacigenic debris flows on the Hudson Strait slope. The Hudson Strait ice stream remained at the shelf break in H3–H5 but retreated rapidly back across the shelf in H0–H2. During this time, Cumberland Sound ice twice reached the shelf edge. Therefore, our data from the strategically located cores raise doubt about the synchronicity of the maximum extent of ice streams in Hudson Strait, Cumberland Sound, and Lancaster Sound and the retreat or absence of the Hudson Strait ice stream during MIS 3.