Subsurface Stratigraphy and Hydrogeology of the Peterborough Drumlin Field, Southern Ontario, Canada

• Main Author: Lotimer, Leslea
• Other Authors: Eyles, Carolyn, Earth and Environmental Sciences
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Drumlins; Hydrogeology; Stratigraphy; Canada; Crozier; First Nations
• Online Access: http://hdl.handle.net/11375/16072

The Peterborough Drumlin Field in southern Ontario, Canada (PDF; Crozier 1975, Karrow 1981, Boyce and Eyles 1991) is a well-documented and extensive drumlin field that hosts many communities dependent upon groundwater resources. Population growth in the area and concerns for the long-term sustainability of these resources has prompted considerable interest in determining the location, extent and potential productivity of subsurface aquifers in the region. The origin of the drumlins within the PDF is still widely debated, despite many years of study, and there is little understanding of the nature, geometry, and connectivity of aquifers within the Quaternary-age sediments beneath the drumlins. This study involves detailed analysis of sedimentological data available from water well logs from selected drumlins and adjacent low areas (swales) in the PDF. These data are used to investigate the subsurface stratigraphy of the drumlins, contribute to the understanding of drumlin formation, and establish hydrogeological characteristics of drumlins within the PDF. A relatively consistent subsurface stratigraphy can be identified in the studied drumlins consisting of patchy units of sand and gravel overlying a southward sloping bedrock surface, a thick diamict (till) package containing discontinuous coarse-grained sand and gravel units, and surface veneers of sand, silt or clay in low areas (swales) between drumlins. This subsurface stratigraphy can be traced between drumlins and adjacent swales and suggests that the drumlins within the PDF formed largely as a result of subglacial erosion of pre-existing sediment. Two major aquifers can be identified beneath the PDF from the water well records; one is a basal aquifer within fractured bedrock and overlying coarse-grained sands and gravels, and the second (upper aquifer) is formed by the discontinuous zone of sands and gravels within till. These coarse-grained interbeds within the till allow it to function as a ‘leaky aquitard’ and produce groundwater flow pathways that are not easy to predict, may not be high-yielding, and may be susceptible to anthropogenic sources of contamination; these characteristics will likely prevent further development of this aquifer for multi-user (communal) water supply. The Hiawatha First Nations (HFN) community is located within the Peterborough Drumlin Field and has been attempting to find a more sustainable, and possibly communal, groundwater supply in the drumlizined terrain. Examination of lithological and hydrogeological data from water well records together with information obtained from four recently drilled on-site wells allowed for a detailed analysis of the till stratigraphy within this portion of the drumlin field. The stratigraphy identified at this site is consistent with that identified elsewhere in the PDF and a basal bedrock aquifer and an upper discontinuous Quaternary aquifer can be discriminated. It is recommended that the HFN community continue to upgrade/maintain individual private wells in the discontinuous upper aquifer and utilize the basal bedrock aquifer for developments that require greater water yields. This study provides insight into the subsurface stratigraphy that may be found beneath drumlins in an extensive drumlin field and may help in determining the origin of these enigmatic landforms. Enhanced understanding of the hydrogeological characteristics of Quaternary-age sediments underlying drumlin fields will assist in the development of appropriate exploration, protection, and remediation strategies for valuable groundwater resources. Thesis Master of Science (MSc)