Recent mapping confirms the threefold division of the glacial record in the area postulated earlier by Warren (1954) and Stalker (1960). Evidence for a fourth early glaciation has been found only in the South Nahanni National Park (Ford, 1975), in contrast to the three pre-Bull Lake events reported from Glacier National Park, immediately to the south of Alberta (Richmond, 1965b). The oldest relatively widespread tills are the Albertan till from the Rocky Mountains and the Labuma till from the Laurentian Shield area. They appear to be Illinoian or earlier in age. They were followed by strong weathering and considerable erosion, together with deposition of the Tofield sands. The next glacial event produced extensive piedmont lobes of Rocky Mountain ice (the Maycroft glaciation) followed closely by the Maunsell ice from the east. Deposits of this age are particularly well preserved in the area south of Nanton. Meltwater formed extensive proglacial lakes which drained southward. This glaciation appears to have been Illinoian or early Wisconsinan in age, and was followed by a nonglacial event during which the Strathcona sands and silts may partly have been formed. The final event was Late Wisconsinan and consisted of the more limited Bow Valley glaciation, forming large prominent lobes near the main present-day centres of cirque glaciation, and the Lochend ice advance from Hudson Bay. At least five subdivisions of the Bow Valley glaciation have been postulated, and ice did not retreat to the present position until about 8000 years B.P. in the Banff-Jasper National Parks (Harris and Howell, 1976) and 7000 years B.P. in South Nahanni Park (Ford, 1975; 1976). The Altithermal period may have finally produced the rapid ice retreat. The Buffalo Lake ice stagnated in many areas, persisting locally until 9600 years B.P. (Boydell, 1972). The most extensive Neoglacial event appears to have been the last (Luckman, 1975).

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