The Pleistocene sediments in the vicinity of the City of Edmonton were mapped on a scale of two miles to one inch. The results of this mapping, combined with a study of aerial photographs and some mechanical analyses, were used in an effort to determine the history of the lake, defined as Lake Edmonton, which existed in this area during the retreat of the continental ice sheet, and the genesis of deposits associated with this lake.

Lake Edmonton deposits were found to have covered an area of approximately 870 square miles within the map area, and to have extended an undetermined distance beyond the map area to the north, south and possibly the west. Lake Edmonton was blocked by glacial ice on its eastern shoreline and probably, in part, on its northern and southern shoreline.

The history of Lake Edmonton was divided into two stages. Stage I began when the wasting of the continental ice sheet had proceeded far enough to permit the deposition of the first permanent lacustrine materials within the area, and finished with the incision of the Gwynne Outlet and partial draining of the lake. Stage II began at this point and ended when further wasting of the ice in the northeast permitted complete draining of the lake.

Lake deposits of Stage I consist of material derived from the adjacent ice and from the large delta built into the lake from the west. Deposits of Stage II also consist of material from the adjacent ice and a lesser amount from the delta to the west. Earlier deposits were modified by the drop in lake level caused by the incision of Gwynne Outlet, the action of inwash waters from the west and later wind action.

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