SURFICIAL MAPPING WITH A TWIST

The Ontario Geological Survey Groundwater Initiative has been producing regional-scale three-dimensional (3D) Quaternary sediment models as inputs for groundwater flow modeling and to provide geologic context for land use planning in southwestern Ontario since the early 2000s. With a strong emphasis on mentoring, student assistants participating in these projects have a unique opportunity to experience a broad range of data collection methods from surficial mapping and logging high-quality sediment cores to geophysical surveys and compiling subsurface databases.

The 1500 km² Guelph area 3D project falls within Ontario’s Greater Golden Horseshoe Growth Plan Area and includes four Urban Growth Centers as well as future transportation and high-speed rail corridors. This area is largely dependent on groundwater for drinking, agriculture and industry and rapid growth is compounding existing pressures on the resource. Existing 1:63 360 scale mapping was completed in the previous century but refinements are required in advance of 3D modeling while the explosion of provincial and municipal infrastructure, capital building and private development projects calls for more detailed 1:20 000 scale mapping.

An Ontario Geological Survey – Carleton University mapping Honours Project is focused on combining traditional surficial mapping techniques of landform identification and ground-truthing with deeper subsurface data collection required for 3D modeling. Lidar-derived digital surface models are now available across the project area facilitating the identification of predominantly late-glacial landforms. Four distinctly different moraine systems separating zones of streamlined bedforms, extensive outwash channels, eskers and fans are revealed recording a complex deglacial history. In thin drift portions of the project area approaching the Niagara Escarpment, hand augering to either consolidated till or bedrock was prioritized over collecting multiple datapoints within the same or similar features. Here bedrock ridges separate wetlands underlain by sediments ranging from sand and gravel to silt and clay-rich glaciolacustrine deposits and diamicton. It is anticipated that there will be additional refinements to existing knowledge as the project moves from primary data collection to interpretation and mapping.