Quaternary Geology and Dispersal Patterns, Winagami Region, Alberta

The Quaternary geology of the Winagami study area is consistent with at least one Late Wisconsinan glacial advance of the Laurentide Ice Sheet. Glacial sediments of possible earlier advances are present, but their chronostratigraphic relationship is speculative. Surficial deposits are associated with ice advance and stagnation, deglaciation and post-glacial processes. Till, glaciolacustrine silt, clay and diamict blanket the majority of the region. Sediments of the glaciofluvial, aeolian, colluvial, alluvial and organic origin are widespread, but of limited areal extent.

Distribution of the surface units and ice directional landforms indicates that the Laurentide ice Sheet varied in thickness and thermal basal regimes during the Late Wisconsinan advance. The dominant ice flow direction was south to southwest and corresponds with the main advance of the ice sheet when ice thickness was at a maximum. The southeasterly ice flow direction was topographically controlled and corresponded with thinner ice lobes marginal to the ice sheet, during the initial stages of ice advance and deglaciation. The Laurentide Ice Sheet was primarily warm-based, with localized regions of cold-based ice.

The stratigraphy of the Winagami region is complex due to the irregularity of drift thickness and bedrock topography. Drift thickness varies from a veneer on topographic highs to over 150 m within the paleochannels. At least six infilled paleochannels of variable depth are present within the study area, although their exact geometry remains unknown. Stratigraphic correlation of the units within these channels is problematic due to the lack of samples and radiometric ages.

Dispersal patterns based on granulometry, lithology, geochemistry and diamond indicator minerals (DIMs) are of limited use in defining dispersal trends due to sample distribution and concentration. Till matrices display homogeneity within three metres of the till - substrate contact, indicating rapid rates of substrate debris entrainment and dilution within the till column. Terminal grade of the entrained material determines the preservation rate of anomalous material within the till column, and can be used to determine glacial transportation distances. In the study area, low and high terminal grades of the underlying bedrock units and the DIMs, respectively, in conjunction with the position of anomalous samples within the till column, indicate debris entrainment within the ice was rapid and the distance of transport was short. Most anomalous samples appear to have come from sources within a few kilometers distance. In the Puskwaskau region, the sources are even closer, likely within one kilometre. Dispersal patterns or trends can be a significant tool in exploration in the Winagami area, provided that they are analysed in conjunction with bedrock topography, drift thickness and glacial history.