The geology and hydrogeology of buried bedrock valley aquifers on Cape Breton Island, Nova Scotia: an overview

Résumé

Buried bedrock valley aquifers are common across Canada, where multiple glaciations have buried both pre-glacial and Pleistocene valleys. These aquifers are becoming increasingly important as a supply of potable groundwater, for supporting aquatic habitat, and as part of strategies in adapting to a changing climate. However, in Canada, there are considerable knowledge gaps at national, regional, and local scales, such that many buried bedrock valleys remain unidentified or underexplored. Cape Breton Island provides a hydrogeological view into the roots of an ancient mountain range, now exhumed, glaciated, deglaciated, and tectonically inactive. Since the Cretaceous, a variety of geological processes have formed several buried bedrock valley aquifers over the island. These aquifers are important in providing municipal and commercial groundwater supplies, controlling mine dewatering, protection of salmonids, design and monitoring of waste disposal sites, and geotechnical investigations for infrastructure design. Of 150 sites assessed, 61% provided evidence of buried aquifers comprising unconsolidated sand and gravel of Cretaceous, Pleistocene, and Holocene ages. These sites provided the basis for five conceptual, 3-D hydrogeological block models. Three hydrogeological case studies provided further insight into the functioning of two of these models. Future studies should identify and characterize aquifers in high demand areas and/or those that support important riverine ecosystems. Research should focus on aquifer properties, groundwater-stream interaction, and the impact of changing climate with sea-level rise.