Late Wisconsinan fluctuations of the Huron, Georgian Bay, Ontario, and Erie glacial lobes gave rise to a complex sequence of interfingering till sheets in the area between Stratford and Toronto, Ontario.
Tills are the basis of establishing the stratigraphy of the area because of their distinctive and consistent characteristics. New names (Tavistock Till, Stratford Till, Stirton Till, Mornington Till, Elma Till, Maryhill Till, Pottery Road Formation) are proposed to replace previous informal names. The extent of Wentworth Till and Halton Till is revised. Subdivision of the Thorncliffe Formation into three members and dropping of the name Leaside Till are proposed.
While a small area of older till is exposed between Woodstock and Waterloo, most tills are of Port Bruce Stadial age, and some are of Port Huron Stadial age. Probable Middle Wisconsinan interstadial deposits are now known from the interior of southwestern Ontario, as well as from previously described sites near Lake Erie and Toronto.
Although over 16,600 sq km of mapping has been carried out in the region in the last 15 yr, only the deposits of the Erie and Ontario glacial lobes are relatively well known; sequences of Huron and Georgian Bay lobe deposits remain inadequately known or poorly understood.