| Title | Electrical resistivity surveys, Vars-Winchester esker aquifer, Ontario |
| Download | Downloads |
| |
| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Oldenborger, G A |
| Source | Geological Survey of Canada, Open File 8769, 2021, 67 pages, https://doi.org/10.4095/328037  Open Access |
| Image |  |
| Year | 2021 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This publication is related to Borehole electrical
resistivity, Vars-Winchester esker aquifer, Ontario |
| File format | pdf |
| Province | Ontario |
| NTS | 31G/06 |
| Area | Embrun; South Nation River |
| Lat/Long WENS | -75.3192 -75.2931 45.3108 45.2722 |
| Subjects | hydrogeology; surficial geology/geomorphology; geophysics; Nature and Environment; Science and Technology; postglacial deposits; marine sediments; muds; glacial deposits; glacial landforms; eskers;
gravels; sands; clays; silts; groundwater resources; aquifers; boreholes; geophysical surveys; geophysical logging; resistivity logging; electrical resistivity; induced polarization; conductivity; models; water table; salt; watersheds; field methods;
groundwater regimes; Vars-Winchester Esker Aquifer; Champlain Sea Sediments; Data processing; Phanerozoic; Cenozoic; Quaternary |
| Illustrations | location maps; photographs; profiles; models; cross-sections; sketch maps; plots; time series; histograms; geophysical logs |
| Program | Groundwater Geoscience Aquifer Assessment & support to mapping |
| Released | 2021 02 19 |
| Abstract | (Summary)
This Open File reports on results of electrical resistivity surveys performed over the Vars-Winchester esker aquifer near Embrun, Ontario as part of the Natural Resources Canada
Groundwater Geoscience Program. Electrical resistivity and induced polarization data were acquired within boreholes as 1D logs, along the surface as 2D profiles, and from surface-to-borehole in 3D. The data were processed and inverted to recover 1D,
2D and 3D models of electrical resistivity and chargeability. The resulting models clearly indicate a resistive esker feature thickest at the centre and thinning on the flanks. The 2D profiles show a more resistive esker centre consistent with a
gravel core under sand cover that is supported by the 1D and 3D models. The base of the esker is not clearly resolved in the resistivity models due to the weak contrast of the esker/basement contact that is below the depth of investigation of the
surface surveys, and subject to high uncertainty in the surface-to-borehole surveys. The resistivity models reveal significant and coherent electrical layering within the conductive Champlain Sea sediments surrounding the esker. Electrical
resistivity is observed to decrease with depth below the water table in the marine muds. Above the water table, the unsaturated zone exhibits anomalously low resistivity that may result from accumulation of salt and other potential electrolytes in
road- and crop-side ditches. Chargeability is measurable at the site for the given experiments. Vertical structure of apparent chargeability is evident in the 1D borehole logs. The gravels and sands appear most chargeable, but the normalized
chargeability suggests dominantly electrolytic conduction with largely uniform surface conduction. No meaningful chargeability models can be recovered for the 2D or 3D surveys, presumably due to the small values of chargeability and high noise
levels. |
| Summary | (Plain Language Summary, not published)
The Vars-Winchester aquifer system consists of a subsurface glacially-deposited esker approximately 40 km in length extending a few hundred meters in
width. The communities of Vars and Limoges both exploit the aquifer for municipal drinking water, along with many domestic and agricultural users. As part of the Natural Resources Canada Groundwater Geoscience Program, geophysical surveys were
performed over the Vars-Winchester esker aquifer near Embrun, Ontario as part of an effort to develop methods of aquifer mapping and characterization for archetypal aquifers. Results of the geophysical surveys are used to quantify the electrical
properties of the sediments that comprise both the aquifer and the aquiclude. |
| GEOSCAN ID | 328037 |
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