The Wisconian glaciation (circa 60,000 years ago) brought severe cold. The water level of the glacial lake rose to 150 feet above the present Lake Ontario level. A large delta of clay and sand (the Scarboro bed) formed in the lake. The pollen and fossils found in the Scarboro bed showed the drop in temperature. The fossils from this bed differed from those of the Don Bed. There were a few tiny shells (no unios), mosses, seeds, small leaves of swamp plants, and the remains of beetles and other insects. The sand was "cross-bedded" indicating it had come from shallow water. The two sections came together to form a delta built by a large river that came in from the north. The sand bluffs at Scarborough are deltaic sands indicating evidence of a very large ancient lake.

The Laurentide ice sheet came (circa 25,000 years ago) across Southern Ontario and Northern United States leaving behind it the "Northern Till" in the Toronto area. Lake Iroquois was formed approximately 12, 500 years ago, much of downtown Toronto is built on the floor of Lake Iroquois. This ice retreated 13, 000 years ago.

The 12th International Congress of Geologists was held in Toronto in 1913. A.P. Coleman was involved with many aspects of the Congress. He was a member of the Organizing Committee, he presented papers at the Congress, he organized excursions in Toronto to look at the city’s glacial topography, gave on site lectures, and contributed to the congress’ excursion guidebooks for Sudbury and Toronto. It was an opportunity for Coleman to present his findings on the Pleistocene Ice Age of Toronto.