10Be dating of former glacial Lake Naskaupi (Québec-Labrador) and timing of its discharges during the last deglaciation

The last deglaciation of the Laurentide Ice Sheet in northern Quebec and Labrador led to the formation of several glacial lakes that drained into Ungava Bay and the nearby Labrador Sea. Assessing the potential impact of their drainage on ocean surface conditions and climate, however, is limited by the few existing age constraints on ice retreat and associated evolution of these lakes. Here we report 21 10Be ages from shorelines and an outburst flood landform formed by Lake Naskaupi, one of the largest glacial lakes in this region. The results indicate that the lake drained from its full extent at 8300 ± 300 a, suggesting that it may have contributed to the freshwater forcing initiated by the drainage of Lake Agassiz-Ojibway that caused the 8.2-ka cold event. Additionally, the results provide important constraints on the position of the ice margin of the Labrador Sector during its retreat across this region.