A Laurentide outburst flooding event during the last interglacial period

Episodes of ice-sheet disintegration and meltwater release over glacial-interglacial cycles are recorded by discrete layers of detrital sediment in the Labrador Sea(1,2). The most prominent layers reflect the release of iceberg armadas associated with cold Heinrich events(3), but the detrital sediment carried by glacial outburst floods from the melting Laurentide Ice Sheet is also preserved(4). Here we report an extensive layer of red detrital material in the Labrador Sea that was deposited during the early last interglacial period. We trace the layer through sediment cores collected along the Labrador and Greenland margins of the Labrador Sea. Biomarker data, Ca/Sr ratios and delta O-18 measurements link the carbonate contained in the red layer to the Palaeozoic bedrock of the Hudson Bay. We conclude that the debris was carried to the Labrador Sea during a glacial outburst flood through the Hudson Strait, analogous to the final Lake Agassiz outburst flood about 8,400 years ago, probably around the time of a last interglacial cold event in the North Atlantic(5). We suggest that outburst floods associated with the final collapse of the Laurentide Ice Sheet may have been pervasive features during the early stages of Late Quaternary interglacial periods.