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Paper No. 88-8
Presentation Time: 3:25 PM

DEVELOPMENT OF A 3-D HYDROSTRATIGRAPHIC MODEL FOR THE BEDROCK OF SOUTHERN ONTARIO


CARTER, Terry, Carter Geologic, London, ON N6K 3P4, Canada, RUSSELL, Hazen .A.J., Natural Resources Canada, Geological Survey of Canada, 601 Booth St, Ottawa, ON K1A 0E8, Canada, FORTNER, Lee D., Ontario Ministry of Natural Resources and Forestry, Petroleum Operations, 659 Exeter Road, London, ON N6E 1L3, Canada, CLARK, Jordan K., Oil, Gas and Salt Resources Library, 669 Exeter Road, London, ON N6E 1L3, Canada, LOGAN, Charles E., Natural Resources Canada, Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada and SUN, Shuo, University of Western Ontario, London, ON N6A 5B7, Canada

Groundwater movement in the subsurface is best understood when viewed in three dimensions. A regional lithostratigraphic 3-D model consisting of 56 layers has been developed for southern Ontario covering 110,000 km2 with a modelled volume of over 75,000 km3. The principal source of data is the nearly 250,000 formation top and bottom depths in 27,000 wells from the Ontario Petroleum Data System, supplemented by measured sections, control points, selected Michigan borehole records and Ontario Geological Survey test boreholes. To support optimal use of the 3-D geological model the lithostratigraphy has been classified as 14 hydrostratigraphic layers within three distinct hydrochemical regimes: brines (deep), brackish-saline sulphur water (intermediate) and fresh (shallow). The uppermost three hydrostratigraphic units consist of a surficial sediment unit, a contact aquifer, and shallow karst. The remaining 11 hydrostratigraphic units consolidate the lithostratigraphy to the Precambrian basement. Hydrostratigraphic assignment is based on shared lithological, sedimentary and diagenetic features, hydrochemistry, and hydrogeological expression as either aquifers or aquitards. Fluid flow in the subsurface is controlled by karst development at regional unconformities, both ancient and recent (<10,000 yr), as well as sedimentary facies, diagenesis and dolomitization. Some lithostratigraphic units occur as aquifers within the shallow karst and as aquitards within the intermediate/deep regime. The distribution and extent of the shallow karst commonly correlates with bedrock subcrop. Mapping suggests the fresh water regime is limited to depths of <250 m. The hydrostratigraphic unit assignment provides a standard nomenclature and definition for regional flow modelling of potable water and deeper fluids. The classification of the lithostratigraphic layers provides model layers suitable for import and discretization in groundwater modelling software.

Session No. 88

T141. Three-Dimensional Geological Mapping to Support Societal Development I
Tuesday, 27 October 2020: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol 52, No. 6
doi: 10.1130/abs/2020AM-356180
© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
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