Browsing by Author "McPherson, Harold James"

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    The Glacial geomorphology of the Upper Red Deer River Valley, Alberta
    (1963) McPherson, Harold James; Nelson, James Gordon
    The major purpose of this study was to describe and interpret in terms of process the landforms created during the deglaciation of the mountainous upper Red Deer river valley. A review of the literature suggested two possible ways in which ice may have retreated during deglaciation. The ice may have re­treated in a series of stillstands with recessional positions of the ice marked by end or recessional moraines and associated outwash deposits. Or alternatively, the ice may have stagnated and retreated mainly by melting and lowering in place. This latter idea, first suggested by the Scandinavian school of geomorphologists has been applied to the interpretation of the landforms of the Canadian prairies. Until the present study, however, its possible applicability to alpine landforms in Alberta had not been investigated. The procedure in this study was to map various kinds of drift in the upper Red Deer valley and to interpret the deposits from the stand­point of deglacial process. In addition, detailed studies in the Red Deer river channel were begun. Stakes were placed by plane tabling at a number of localities in the channel with a view to measuring rates of channel erosion and deposition, and the factors controlling these, over a period of several years. Observations reveal differences in the textural and structural character of the deposits, in and around the stream channel in front of the Drummond Glacier and similar deposits located farther downstream. The material close to the ice contains much more poorly sorted and stratified material. Downstream in places, wide alluvial flats occur, and these are composed pre­dominantly of subrounded to rounded stratified and sorted gravels and fines. The presence of poorly stratified and poorly sorted material close to the ice indicates that material of outwash type is not forming in quantity in front of the ice today. This, in turn, suggests that the braided alluvial flats located farther downstream may not be outwash, when the term outwash means proglacial deposits washed out from the ice. Rather the alluvial flats located farther downstream may have been formed by fluvial erosion and deposition some time after ice retreat and some appreciable distance from the ice. Measure­ments of contemporary erosion and deposition on the alluvial flats, will permit estimations to be made of present day rates of change, and will serve as one kind of check on the idea of "Postglacial" creation of the flats. Mapping of surficial deposits in the valley reveal the pre­dominance of depositional material considered to have been laid down close to melting ice. This ice proximus material gives rise to either hummocky topography or to a non-paired series of benches which parallel the river in places. Throughout the valley there exists a paucity of landforms which can be identified as recessional or end moraines, and also of out­wash deposits associated with these. This, combined with the predominance of ice proximus material, indicates that the ice retreated not by a series of stillstands during deglaciation, but rather by stagnation and lowering in place.