Surficial Geology of the Edmonton District, Alberta

The Edmonton district was glaciated during Wisconsin time by a continental glacier which advanced over the area from the central region of Keewatin. This glacier at the time of maximum extension covered most of Alberta and attained a thickness of about one mile over the map area. The retreat of the glacier from central Alberta was largely by stagnation. As the natural drainage of central Alberta is northeasterly and as the glacier retreated in that same direction, meltwaters were impounded in front of the glacier producing large, relatively short-lived lakes many hundreds of square miles in area. The rapid recession of the stagnating glacier allowed these proglacial lakes to find constantly new and lower outlets. As a result of this, the proglacial lakes in Alberta as a rule have no beaches associated with them.

One such proglacial lake, Lake Edmonton, at one time covered most of the Edmonton district and extended far to the west. Only the very eastern part of the district and a small area in the northwest were not covered by Lake Edmonton; these areas are devoid of lacustrine sediments, the surface deposit being till. The surface of the lacustrine deposits is for the most part flat, but in places has a very rough topography, a function both of conditions of sedimentation in the lake and of the topography of the underlying materials. Lake Edmonton was drained finally by the North Saskatchewan River in post-glacial time. During the Altithermal period, the climate of the area was much warmer and drier than at present. At this time most of the sand dunes in the area were probably formed.