POSTGLACIAL FORESTS IN SOUTH CENTRAL ALBERTA, CANADA

Abstract

Peat sections were obtained from four bogs along the Edmonton-Jasper highway in west central Alberta. These bogs lie at distances of about 30, 55, 85, and 125 miles west of Edmonton. More specifically they are located about 4 miles north of Duffield, 4 miles east of Entwhistle, near the town of McKay, and about 5 miles west of Edson, respectively. Hereafter they will be referred to as the Duffield, Entwhistle, McKay, and Edson sections or bogs. All sites lie within the westernmost border of the Keewatin drift. Although the Cordilleran glaciers descended the east slope of the Rocky Mountains in this latitude, the relationships between the two ice sheets and the borders of their drifts are uncertain. It is evident, however, that the Keewatin ice was more extensive in this region, because the Cordilleran glaciers were probably limited by the relatively low precipitation on the east slope of the mountains. One stage of the Cordilleran glaciers descended the eastern flanks of the Rockies to points 50 miles east of the mountains in the vicinity of Calgary, and still farther east in the latitude of Edmonton (Flint 1947). During one or more stages the Cordilleran and Keewatin ice may have coalesced, but there is no evidence that their fronts were joined during the Late Wisconsin (Mankato) stage in west central Alberta. It seems probable that the last glacier in the region was of Keewatin origin. Keewatin boulders have been noted as far west as Edson, although no end moraines have been observed in this area (Erdtman & Lewis 1931). The eastern border of the Altamont moraine, which is dated as terminal Late Wisconsin, lies about 75 miles east of Edmonton (Bretz 1943). It is considered to be equivalent to the Mankato maximum of the Minnesota-Iowa region. West of the Altamont moraine in the general latitude of Edmonton are older Keewatin moraines. The westernmost and oldest of these is the Duffield moraine, whose eastern border lies about 25 miles west of Edmonton. Although the Duffield moraine is older than the Altamont, its topography is much more youthful than the Early Wisconsin (Iowan) drift in Montana (Bretz 1943). In a previous paper (Hansen 1949) it was suggested that the Duffield was equivalent to the Tazewell or Cary of the eastern ice, although geologists have not recog-