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TitleMultidisciplinary geoscience insights on the western Champlain Sea regional aquitard
 
AuthorHinton, M JORCID logo; Alpay, SORCID logo; Crow, H LORCID logo; Dietiker, BORCID logo; Al, T A; Celejewski, M A; Al-Mufti, O N; Arnott, R W C; Russell, H A JORCID logo
SourceRegional-sScale Groundwater Geoscience in Southern Ontario: The 2021 Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario Geoscientists Open House; by Priebe, E H; Ford, D; Holysh, S; Nadeau, J E; Russell, H A JORCID logo; Ontario Geological Survey, Open File Report 6378, 2022 p. 14 Open Access logo Open Access
LinksOnline - En ligne
Image
Year2022
Alt SeriesNatural Resources Canada, Contribution Series 20200744
PublisherGovernment of Ontario
MeetingRegional-sScale Groundwater Geoscience in Southern Ontario: The 2021 Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario Geoscientists Open House; February 16 & 18, 2021
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
ProvinceOntario
NTS31G/05
AreaOttawa; Bilberry Creek
Lat/Long WENS -76.0000 -75.5000 45.5000 45.2500
Subjectshydrogeology; surficial geology/geomorphology; geophysics; geochemistry; Nature and Environment; Science and Technology; groundwater resources; groundwater flow; marine sediments; muds; sands; boreholes; geophysical surveys; seismic surveys; geophysical logging; conductivity; magnetic susceptibility; piezometric levels; observation wells; core samples; pore water samples; groundwater geochemistry; salinity; permeability; Champlain Sea Sediments; Phanerozoic; Cenozoic; Quaternary
ProgramGroundwater Geoscience Aquifer Assessment & support to mapping
Released2022 02 25
AbstractThe Rideau Valley Conservation Authority (RVCA) and the City of Ottawa initiated a hazard mapping study to identify flood risk and slope stability hazards along Bilberry Creek in Orleans, a suburb of Ottawa, Ontario. The study provided two cored boreholes for the Geological Survey of Canada (GSC), in collaboration with the University of Ottawa, to investigate pore water, geochemical, and physical influences on the geotechnical properties of Champlain Sea muds and their susceptibility for landslide events. Further research objectives are to characterize the hydrogeology of the regional aquitard and to establish two new reference sites in Champlain Sea sediments. The multidisciplinary geoscience approach will foster improved analysis and interpretation to support regional-scale understanding of the Champlain Sea aquitard in the Ottawa region.
A geophysical survey of ambient seismic noise was used to estimate soft sediment thickness and identify two drilling sites in thick Champlain Sea deposits. The drilling program yielded 147 Shelby tubes of sediment, 2 casings to depths 46 m and 67 m for downhole geophysical logging, 4 vibrating wire piezometers and 2 monitoring wells. Computed tomography (CT) scans provided sub-millimetre-scale imagery of sediment cores. Core extrusions and analyses of pore water and sediment samples are in progress.
Borehole geophysical logs of apparent conductivity and preliminary pore water chemical measurements indicate a substantially lower remnant seawater signature (15%) as compared to previous GSC studies of thick (>40 m) Champlain Sea sequences at Breckenridge, Quebec (63%) and Kinburn, Ontario (88%). The lower relic salinity at Bilberry Creek indicates greater displacement of connate seawater. In borehole geophysical logs, magnetic susceptibility anomalies suggest the possible occurrence of relatively coarser grained horizons. Similarly, CT scans reveal thin layers of higher density sediment, possibly coarser grained (e.g., very fine sand), interbedded with the mud. These observations suggest that higher permeability layers can allow for lateral flow within the Champlain Sea aquitard, providing opportunity for freshwater ingress and enhanced diffusion-driven outflux of solute.
Summary(Plain Language Summary, not published)
This study examines sediment and pore water from two cored boreholes near Bilberry Creek in Orleans, Ottawa. The objective is to investigate water and sediment influences on the geotechnical properties of Champlain Sea muds and their susceptibility to landslides. Further objectives are to understand groundwater flow through the mud and to establish two new reference sites. A multidisciplinary geoscience approach will support understanding of the Champlain Sea sediments in the Ottawa region. Initial results indicate lower remnant seawater content (15%) as compared to previous GSC studies of thick (>40 m) Champlain Sea sediments at Breckenridge, QC (63%) and Kinburn, ON (88%). The lower relic salinity at Bilberry Creek indicates greater displacement of fossil seawater. The possible occurrence of relatively coarser-grained horizons suggest that these layers can allow for lateral groundwater flow, providing opportunity for fresh water to flush out salt water from the sediments.
GEOSCAN ID328100

 
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