Detailed clay mineralogical characterization was completed on four major glaciogenic surficial deposits in northeastern Alberta. The mineral species identified and quantified were mica, montmorillonite, beidellite, kaolinite, chlorite, and vermiculite. Although there were quantitative differences in the amounts of mica, kaolinite, and chlorite in the Legend unit, the similarity of the mineral species in all deposits precluded their use for a definitive assessment of sediment provenance.Oxygen isotopic data for the clay separates served as a useful criterion for differentiation of deposits. Differences in isotopic signature were related to the inclusion of materials from the underlying Cretaceous marine sediments and to the admixture of materials from preweathered Shield sediments. The difference in isotopic signature of the clay separates was specifically related to the formation conditions of the micaceous component.