Flute-forming conditions in Alberta and North Dakota: A comparison using ice sheet reconstructions and field techniques

The conditions associated with the development of glacial flutes were determined by reconstructing ice thicknesses, basal shear stresses, and examining field properties of sediments in three areas. The morphologically similar Saskatchewan Glacier Valley in Alberta, Canada, and the Kiwa Glacier Valley in British Columbia, Canada, were compared to understand why flutes were developed in the former and not the latter. These results were compared to a similar study northwest of the Martin Moraine in north-central North Dakota.; A former ice surface was reconstructed for the Saskatchewan and Kiwa Glaciers by applying the equations of existing glacier longitudinal profile lines to a terminus downvalley. For the Martin Moraine position, a reconstructed ice surface was calculated using mathematical approximations of former longitudinal profile lines.; After subtracting the elevation of the land surface from that of the reconstructed glacier surface, and calculating former ice surface slope, ice thickness and basal shear stress distributions (representing minimum sediment strength) were plotted. Reconstructions for the Saskatchewan Glacier and Martin Lobe seem reasonable but differences in valley morphology between the existing Kiwa Glacier and the former terminus downvalley result in questionable ice thickness and basal shear stress plots.; Approximation of sediment strength using Coulomb's equation, and observation of the similarity in reconstructed ice thickness for the Saskatchewan and North Dakota studies, indicate the development of porewater pressure is crucial for flute formation.; Sediment texture and the location of flutes on a topographic high, downglacier from a proglacial lake basin, allowed high porewater pressures to develop as glaciers extended to terminus positions. Lack of flutes in the Kiwa Glacier area is attributed to the absence of a similar topographic high.; Development of subglacial tunnels, during times of high porewater pressure, and subsequent deposition, and deformation of sediment as porewater pressure decreased, would result in an accumulation of both convoluted and stratified sediments as observed in an excavation across Hogback Ridge, northwest of the Martin Moraine. This supports the conclusion that high porewater pressure is important in the development of glacial flutes.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows 95 or higher; Microsoft Office.