During glaciation, till sheets were deposited over the Saskatchewan Sands and Gravels and the bedrock (where exposed). As the glaciers retreated to the northeast, they stagnated north of Edmonton resulting in the formation of a large proglacial lake called glacial Lake Edmonton. Meltwater from the ice sheet deposited sediment into this glacial lake. The glacial lake deposits extend over most of the Edmonton area and comprise fine-grained glaciolacustrine sand, silt and clay.