Sunnybrook drift indicates a grounded early Wisconsin glacier in the Lake Ontario basin

Glaciotectonic analysis of Sunnybrook diamicton and underlying sediments in Scarborough Bluffs, Ontario, Canada, indicates that the diamicton investigated is lodgment and/or deformation till. The early Wisconsin overriding of deformable glaciolacustrine mud by the Ontario ice lobe was a significant glacial event in the eastern Great Lakes region. This has important implications for understanding interactions between Laurentide ice, proglacial lakes, and water-laid sediments.