ABSTRACT

Quaternary age sediment covers almost all of the bedrock within the western plains. Prior to glaciation, the plains consisted of low uplands cut by generally northeast-trending valleys. The Laurentide glaciers advanced across the plains at least five times. Deposition during both the glacial and nonglacial events produced, in many areas, a complex stratigraphy composed of glacial diamicton (till), and stratified, predominantly lacustrine and fluvial, sediment. This sediment, characterized by clasts from Precambrian and Paleozoic units, varies from 300 m thick in a few pre-glacial valleys to less than a metre on some of the interfluves.

Multiple till sequences can be traced over wide areas utilizing composition and downhole geophysical data. These diamictons generally form aquicludes confining a series of aquifers in the stratified sediment. The Sand River map area, for example, which covers much of the Cold Lake Oil Sand Deposit, includes eight glacial and nonglacial formations. Drift thickness varies from about 50 m to 300 m. The coarser grained portions of a number of the stratified units, such as the Muriel Lake and the Sand River formations, contain aquifers that represent a major source of groundwater.

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