TOWARD A 3-D HYDROSTRATIGRAPHIC FRAMEWORK FOR SOUTHERN ONTARIO

Following 10 years of groundwater (GW) studies as part of Ontario’s Source Water Protection Program and groundwater mapping initiatives of the Ontario Geological Survey (OGS), there is an opportunity to consolidate geologic and GW information and maximize data accessibility through development of a 3-D hydrostratigraphic framework. The framework will support dynamic GW modelling necessary to study Great Lakes water quality, climate change, drought monitoring, agricultural water management, potable water, and cumulative impacts. To support this initiative, data holdings distributed amongst multiple agencies will require coordination and a distributed database approach. For the Paleozoic bedrock, the principal data source is the Ontario Petroleum Data System (27,000 wells) managed by the Ministry of Natural Resources and Forestry and the Oil, Gas and Salt Resources Library. Available 3-D geospatial information includes geological formation tops, oil/gas/water intervals, geophysical logs, and drill core and cuttings from bedrock formations. Hydrogeological data includes water interval data (depth, elevation, static level, water type and geological formation) and a published regional 2D bedrock aquifer model. For the surficial geology, data management and quality assessment is less advanced. Regional datasets include over 300 continuously cored boreholes and MOECC water well records (~490,000 records). Locally, there are seismic reflection data, downhole geophysics, ground-based gravity and airborne electromagnetics data. To convert these data into a 3D hydrostratigraphic framework requires an iterative process of quality assessment in a hierarchical framework of key control data and secondary data to constrain interpretation. Crucial to the development of the control framework is the integration of field mapping, core logging and geophysical log interpretation that supports development of paleogeographic and depositional / erosional interpretations. Complexities in both the bedrock and surficial geology require an approach to ensure that hydrostratigraphic complexities involving vertical (paleokarst, tunnel valleys, faults) and lateral (facies changes) flow zones and barriers are accounted for. Development of the framework is anticipated to be a 4-year undertaking.