Our reinvestigation indicates that Sunnybrook drift represents a glaciolacustrine-subglacial-glaciolacustrine cycle, the Ontario lobe being the main glacial agent. Glacier ice overrode the present Toronto area during Sunnybrook deposition, deforming the substrate and depositing subglacial till. We propose that Sunnybrook drift comprises three or four members: a diamictic Sunny Point member (mainly till) sandwiched by two glaciolacustrine members (Sylvan Park and Bloor), and possibly a subglacial fluvial member (Pottery Road) associated with till deposition.

The Sylvan Park member represents glaciolacustrine fine sediment that was overridden, deformed, and incorporated by ice that deposited the Sunny Point member. Parallel striated stone pavements, parallel and transverse stone and magnetic fabrics, stone facet and stoss-lee relations, and shear planes within the Sunny Point member indicate that it was formed by a combination of lodgement and subglacial deformation. Deposition under active grounded ice is further supported by the sharply erosive contact of the Sunny Point member with the top of the buried Scarborough delta, as well as glaciotectonic fractures and folds in substrata. Sunnybrook drift deposition concluded with the glaciolacustrine Bloor Member. Regional correlation suggests that the glaciolacustrine members were not formed far inland from the Scarborough Bluffs.