GLACIAL LAKE LOW: A PREVIOUSLY UNIDENTIFIED PROGLACIAL LAKE IN WESTERN LABRADOR

The timing and configuration of retreating ice margins are important to understanding the demise of past ice sheets, and glacial lakes are a key component of these reconstructions. Glacial Lake Low was a previously unidentified proglacial lake of the Laurentide Ice Sheet that formed north of the headwaters of the Churchill River, in lowlands now occupied by the Smallwood Reservoir in western Labrador. Glacial Lake Low formed within a re-entrant into the retreating ice sheet in the Churchill River valley, constrained by a low elevation drainage divide with its outlet at the Churchill River. This glacial lake occupied a basin south of the modern drainage divide along the Quebec and Labrador border. This lake was named after Albert P. Low (1861–1942) of the Geological Survey of Canada, who first recognized in the 1890s that the final disintegration of the continental ice sheet occurred in this region.

Although relatively shallow, glacial Lake Low was aerially extensive and formed well-developed beach ridges that were identified through surficial mapping which indicates the maximum washing limit of the lake was ~ 485 m asl (above sea level). The glacial lake drained following minor isostatic rebounding that resulted in the drainage divide between the Arctic and Atlantic oceans migrating northwest, allowing meltwater to decant south into the Churchill River valley. Waters then ponded in the former basins of Ossokmanuan, Lobstick, and Michikamau lakes, which were merged by the construction of the Smallwood Reservoir, created in 1974 with the damming of the Churchill River at Churchill Falls.