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TitleConceptual hydrogeological model of the Yonge Street Aquifer, south-central Ontario: a glaciofluvial channel-fan setting
AuthorGerber, R E; Sharpe, D R; Russell, H A J; Holysh, S; Khazaei, E
SourceQuaternary geology of southern Ontario and applications to groundwater understanding/Géologie quaternaire du sud de l'Ontario et applications à l'hydrogéologie; by Russell, H A J (ed.); Arnaud, E (ed.); Bajc, A F (ed.); Sharpe, D R (ed.); Canadian Journal of Earth Sciences vol. 55, no. 7, 2018 p. 730-767, https://doi.org/10.1139/cjes-2017-0172
Year2018
Alt SeriesNatural Resources Canada, Contribution Series 20180045
PublisherCanadian Science Publishing
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html; xlsx (Microsoft® Excel®)
ProvinceOntario
NTS30M/13; 30M/14; 31D/03; 31D/04
AreaGreater Toronto Area; Lake Simcoe; Holland Marsh
Lat/Long WENS -79.7000 -79.1833 44.2167 43.8667
Subjectshydrogeology; surficial geology/geomorphology; stratigraphy; geophysics; groundwater resources; aquifers; groundwater regimes; groundwater flow; modelling; glacial deposits; glacial landforms; tills; moraines; sands; gravels; muds; clays; fans; channels; channel deposits; eskers; seismic interpretations; seismic profiles; hydrostratigraphic units; facies analyses; sedimentary structures; permeability; transmissivity; hydraulic analyses; groundwater levels; bedrock geology; water wells; boreholes; depositional environment; water table; potentiometric surfaces; water utilization; geological history; Yonge Street Aquifer; Newmarket Till; Oak Ridges Moraine; Lower Sediment; Thorncliffe Formation; Halton Till; Bradford Aquifer; strip aquifers; glaciofluvial sediments; glaciolacustrine sediments; sediment thickness; diamicton; water supply; aquitards; digital elevation models; hydraulic response; Phanerozoic; Cenozoic; Quaternary; Paleozoic; Ordovician; Cambrian
Illustrationsgeoscientific sketch maps; stratigraphic charts; 3-D models; stratigraphic cross-sections; location maps; tables; seismic profiles; lithologic sections; photographs; correlation sections; models; plots; time series; hydrographs
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
Released2018 07 05
AbstractThe Yonge Street Aquifer (YSA) in the Greater Toronto Area of south-central Ontario is a prolific municipal supply aquifer. It has been considered to be channelized sand and gravel linked to a bedrock valley. Despite considerable work, the fundamental conceptual model for the YSA is not well developed and documented. Based on high-quality data, a revised conceptual model of the aquifer is presented. Seismic profiles define the geometry of the regional stratigraphy with four distinct units: bedrock, Lower sediments, Newmarket Till, and Oak Ridges Moraine (ORM) sediment. Seismic data reveal two generations of roughly north-south channels: older sub-Newmarket Till channels within Lower sediments (termed Thorncliffe channel) and ORM-related channels (termed ORM channel) that incise both Newmarket Till and Lower sediments. The YSA is interpreted to occur within a Thorncliffe channel, with possible vertical connection to younger ORM channels and lateral connection to inter-channel Lower sediments. Thorncliffe channel deposits consist of fining-upward transitions from coarse gravel, to sand, to rhythmically bedded mud interpreted to be deposited within a channel - esker - subaqueous fan complex. Upper Thorncliffe channel mud facies and overlying Newmarket Till provide a capping aquitard. The YSA conceptual model benefits from a strong understanding of facies changes in the Thorncliffe Formation. The deposits with highest permeability occur within up to 80 m thick gravel and sand sequences at the base of the Thorncliffe channel, with transmissivity ranging from 1500 to 4500 m2/day. Groundwater level response to municipal pumping confirms connection along the channel with muted hydraulic response laterally. Thorncliffe channels are interpreted to be up to 20 km long and approximately 2 km wide.
Summary(Plain Language Summary, not published)
The Yonge Street Aquifer (YSA) in the Greater Toronto Area is a prolific municipal supply aquifer that provides water supply to ~250,000 residents. It has been considered as channelized sand and gravel linked to a bedrock valley. Despite considerable work, including groundwater flow modelling, the fundamental geological and hydrogeological framework for the YSA is not well developed and documented. Based on high-quality data, revised conceptual geological and hydrogeological models of the aquifer system are presented. High resolution seismic profiles define the geometry of the regional stratigraphy with four distinct seismic units: bedrock, Lower sediments, Newmarket Till and Oak Ridges Moraine. Key aquifers in the area are NS-orientated channels related to glacial age floods. Channels consist of fining upward transitions from coarse gravel, to sand, to rhythmically bedded mud. Muddy sediments overlie and protect the YSA.
GEOSCAN ID308218