A large number of re-entrants in the Niagara Escarpment, severely indenting the outcrop of the Lockport-Amabel dolomite, are defined and their morphologic characteristics described. These characteristics are believed to have been induced largely by glacial agencies, and various ice movements over the Niagara scarp during the Wisconsin Glaciation are determined from a consideration of moraine and drumlin trends and meltwater drainage lines. Three main phases of ice advance and recession within the Late Wisconsin and a general advance within the Early Wisconsin are envisaged, during which ice repeatedly flowed along and probably greatly enlarged many of the re-entrant valleys.
Large-scale glacial erosion is demonstrated along the Niagara scarp where it fronts onto Georgian Bay, and comparison is made between this area and the Finger Lakes region in New York state. Less intense erosion is considered to have affected the remainder of the scarp, though the Dundas valley is also regarded as a major glacial trough. These conclusions weigh heavily against contentions that recognizable “preglacial” features persist along or in front of the Niagara Escarpment, and a brief re-evaluation of previously postulated “pre-glacial” drainage systems is made.