REGIONAL 3D SURFICIAL GEOLOGICAL FRAMEWORK FOR SOUTHERN ONTARIO

A variety of competing land use and subsurface issues in southern Ontario require an integration of disparate datasets and a single geological–hydrostratigraphic model. A consolidated framework is critical to addressing societal needs under cumulative impacts, and climate change scenarios. In addition to extensive data collection and analysis a surficial 3D geological model has been developed for 66,870 km² terrestrial portion of the area. The model consists of 7 surficial geology layers overlying bedrock. Model development was highly constrained and informed by a well-developed stratigraphic framework that recognized spatial and stratigraphic variability across the study area. The surficial model integrates existing sub-regional (<10,000 km²) 3-D models along with stratigraphically interpreted cored boreholes, geophysical data, continuous geological map data, and topographic DEM model and bedrock topographic DEM, to constrain archival waterwell and geotechnical logs interpretation. Where feasible additional legacy data was captured to supplement available data. A preliminary model based on high-quality interpreted data was used along with surficial geological mapping and expert knowledge in a rules-based algorithm to help assign stratigraphic coding to the widespread, archival borehole data. An iterative cycle of automated and manual coding checked by periodic interim model inspection and revision has led to the 3-D surficial geological model. The framework also integrates geochemical coverage of the area, subsurface geochemical transects and classification of provincial groundwater monitoring network to facilitate integrated data analysis. This model has been integrated into a regional-scale fully coupled groundwater–surface-water flow model. The comprehensiveness of the data support, data integration, and modelling is unique in Canada and demonstrates the multidisciplinary science framework required to support a science-based decision approach to water and land use management.