CGRG Bibliography of Canadian Geomorphology
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Author : Cole, J.; Coniglio, M.; and Gautrey, S.
Date : 2005.
Title : Regional distribution and development of porosity in karstic aquifers in the Guelph area of southern Ontario: Implications for groundwater resources.
Publication : Joint Meeting of the Geological Association of Canada, the Mineralogical Association of Canada, the Canadian Society of Petroleum Geologists and the Canadian Society of Soil Sciences. May 15-18, 2005. Studley Campus of Dalhousie University, Halifax, Nova Scotia.
Issue :
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Abstract
The City of Guelph obtains potable groundwater from deep (30 - 50 m bgs) bedrock aquifers in middle Silurian dolostones. Primary water production is from large cavernous pores, and to a lesser extent, fractured zones within the Guelph and Amabel formations. Hydrogeologists and water well drillers have long recognized that the unconsolidated sediments filling pre-Wisconsin bedrock valleys were prospective sources for groundwater. However, recent analysis of bedrock topography maps and current production well locations shows a spatial relationship between highly productive bedrock aquifers and buried bedrock valleys in the Guelph area. Previous studies of bedrock jointing in southern Ontario have shown that vertical to sub-vertical fractures through the Guelph and Amabel formations are related to regional stresses and parallel the trends of buried bedrock valleys. These fractures may have provided a conduit for groundwater to be transmitted deep into the dolostone. Once at depth, groundwater moved horizontally towards the bedrock valleys and discharged to surface along the valleys. A relatively high flux of unsaturated groundwater discharged into bedrock valleys as a result of increased hydraulic gradients between the incised bedrock and adjacent upland areas, creating favourable conditions for karst development in this highly productive, deep aquifer. Subsequent to the formation of the bedrock valleys and karst, Wisconsin-aged till and glaciolacustrine sediments infilled the bedrock valleys and greatly reduced the efficacy of the groundwater flow system to cause dissolution. This study indicates that identifying buried bedrock valleys in the Guelph area is important for locating aquifers in both unconsolidated infill sediment as well as the adjacent bedrock. Furthermore, knowledge of the distribution of large pores and the origin of this karstic aquifer in the Guelph area will enhance our abililty to protect existing groundwater supplies.
Bibliography of Canadian Geomorphology