CGRG Bibliography of Canadian Geomorphology
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Author : Girard, F.; Parent, M.; Boisvert, E.; Michaud, Y.; Lefebvre, R.; and Martel, R.
Date : 1999.
Title : Three-dimensional Quaternary stratigraphy : application to regional hydrogeological mapping in the Portneuf Area, Quebec, Canada.
Publication : Annual Meeting of the Geological Society of America, Denver, Colorado. October 27–30, 1999. (abstract)
Issue :
Page(s) :
Abstract
A regional hydrogeological mapping project was carried out along the northern margin of the Champlain Sea, a late-glacial marine basin in which entered several large, sediment-laden streams fed by meltwaters from the Laurentide Ice Sheet. The delineation and characterization of unconfined aquifers in deltaic, littoral and morainic sediments of the Portneuf region required the compilation of diverse geoscientific data. Thousands of surface, borehole and geophysical data were integrated in order to assess the surface and subsurface distribution of surficial sediments. These data were used to prepare a series of closely spaced cross-sections and to construct a 3-D stratigraphic model of an area containing the most productive aquifers of the region. This area, called the Saint-Raymond basin, is characterized by a thick widespread unit of fine-grained marine sediments overlain by prodeltaic silty sands and by a thick deltaic sand unit, adjacent to the Saint-Narcisse Moraine. The deltaic sediments which are the largest aquifers were dissected by the Sainte-Anne River during marine regression and resulting in a series of terraces causing a hydraulic break between the aquifers and the river. The Saint-Narcisse Moraine represent a potentially good aquifer but its complex stratigraphy and highly variable sediments make a regional assessment difficult. Subsurface lobes of sandy subaqueous outwash adjacent to the moraine and interfingering with fine grained marine sediments can represent very good confined aquifers, with low vulnerability to contamination. The stratigraphic relationships between these sediments and their relationships with the bedrock topography represent key factors to understand the regional ground water flow. This 3-dimensional model leads to a better understanding of the geometry and architecture of Quaternary units and is a key tool for the delineation of aquifer/aquitard systems and for the identification of confined aquifers. The 3-D mapping leads to a better assessment of the continuity of productive aquifers and to more accurate estimations of aquifer volumes. 3-D models also provides a sound basis for numerical modelling of groundwater flow and for assessing groundwater vulnerability to contamination.
Bibliography of Canadian Geomorphology