In northeastern Ontario there was a large glacial lake, Iroquois, that existed approximately around 13000 years ago. It was a proglacial lake. It was practically an enlargement of today's lake Ontario. It formed because the St. Lawrence River was blocked by an ice sheet, and it drained to the southeast, through a channel passing today's Rome, New York, through the Mohawk River and then in Hudson River. As evidence, there's the sand ridges of Rome, the relief forms in the plains around lake Ontario, the soil structure, the glacial remains.