Abstract
Population growth in the groundwater-dependent municipalities of southwestern Ontario has prompted interest in the exploration for new, previously untapped, groundwater resources. In this study, the groundwater resource potential of the sediments infilling a deeply buried bedrock valley network centred beneath the Region of Waterloo and the counties of Brant and Hamilton–Wentworth are explored. The objectives of this study are to further refine valley location and geometry, understand infilling sediments and their hydrogeological properties, and characterize waters contained within the aquifers to inform future water management decisions. Results of a regional ground gravity survey were instrumental in locating buried bedrock valleys and guided follow-up drilling. Continuous sediment coring and monitoring well installations were completed to target thick and coarse-grained sediment packages that, based on existing borehole data, showed aquifer potential. Hydraulic testing and groundwater sampling results provided valuable insights into groundwater quantity and quality. Highly transmissive aquifers, some worth investigating further, have been identified within portions of the valley network. The aquifers appear to occur at a number of stratigraphic positions and do not necessarily occur as the deepest unit overlying bedrock. Bedrock topography likely played a role, however, in their preferential preservation. They are commonly overlain by thick sequences of relatively impermeable sediments, providing excellent protection from anthropogenic contamination. Information from water chemistry, however, does suggest hydraulic connection to the surface at some locations. Groundwater quality and quantity information combined with a conceptual three-dimensional geologic model aids in the selection of groundwater resource exploration targets within the untapped resources of the deep, Dundas buried valley sediments.
Highlights
A deeply incised buried bedrock valley extending westward from the western end of Lake Ontario has intrigued geologists in southern Ontario for more than a century (Fig. 1) (e.g. Spencer 1890; Straw 1968; White and Karrow 1971; Flint and Lolcama 1985; Eyles et al 1993, 1997; Gao 2011)
It is difficult to determine whether the negative residual anomalies are responding to broad bedrock valleys or perhaps narrower valleys crossed by the survey at an oblique angle
Multiple hypotheses have been proposed for the origin of buried bedrock valleys in southern 629 Ontario
Summary
A deeply incised buried bedrock valley extending westward from the western end of Lake Ontario has intrigued geologists in southern Ontario for more than a century (Fig. 1) (e.g. Spencer 1890; Straw 1968; White and Karrow 1971; Flint and Lolcama 1985; Eyles et al 1993, 1997; Gao 2011). Spencer 1890; Straw 1968; White and Karrow 1971; Flint and Lolcama 1985; Eyles et al 1993, 1997; Gao 2011) Conceptualizations envisioned this valley as part of a large preglacial drainage system centred over the Great Lakes basins (Fig. 1a) (Spencer 1890). Karrow’s (1973) compilation of bedrock topography of southwestern Ontario further refined the locations of buried bedrock features including prominent escarpments, broad, trough-like bedrock depressions and narrow gorges (Fig. 1b) In that compilation, he identified a continuous, buried bedrock valley system extending northwesterly from the west end of Lake Ontario towards the shores of Lake Huron, a distance of over 180 kilometers. Local studies along the trend of the Dundas valley between Lake Ontario and Copetown have, resulted in an improved understanding of the geometry of the bedrock valley and the nature and age of infilling sediments (Finamore 1975; Edgecombe 1999; Greenhouse and Monier-Williams 1986, 1986; MacCormack et al 2005)
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