The Nipissing Great Lakes are not referred to as "Glacial Lake Nipissing" because the ice sheet was no longer present in the region.  These lakes started forming as the North Bay outlet opened up, effectively draining Glacial Lake Algonquin down to the Chippewa-Stanley level.  With time, from 10,000 BP to about 4500 BP, the outlet rose, due to isostatic rebound.  So, as the outlet continued to rise, lake levels also rose--a period in time referred to as the Nipissing Transgression.   Eventually, the lakes rose to a level that was a few meters higher than current lake level, and cut a conspicuous notch (beach ridge) into the landscape to mark this high water stand at 4500 BP.
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