Surficial deposits, ice movements, and glacial lakes are described for an area of 42 000 square miles in northeastern Ontario. Field studies and air photograph interpretation suggest the following sequence of events. A major fan-shaped advance of an ice mass over the study area. This was followed by the withdrawal of the ice mass from the area and the formation of proglacial lakes. This ablation phase was followed by a minor readvance. Two phases are postulated for this 'Cochrane' readvance. Within the study area, the extent of the glacial lakes and the limits of extension of the Cochrane readvance are postulated. A maximum water plane, location, and maximum elevation of outlet and amount of differential uplift of sediments are postulated for glacial Lake Barlow–Ojibway.