| Title | Conceptual hydrogeological model of the Yonge Street Aquifer, south-central Ontario: a glaciofluvial channel-fan setting |
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| Author | Gerber, R E; Sharpe, D R ; Russell, H A J; Holysh, S; Khazaei, E |
| Source | Quaternary 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  Open
Access |
| Year | 2018 |
| Alt Series | Natural Resources Canada, Contribution Series 20180045 |
| Publisher | Canadian Science Publishing |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®); html; xlsx (Microsoft® Excel®) |
| Province | Ontario |
| NTS | 30M/13; 30M/14; 31D/03; 31D/04 |
| Area | Greater Toronto Area; Lake Simcoe; Holland Marsh |
| Lat/Long WENS | -79.7000 -79.1833 44.2167 43.8667 |
| Subjects | hydrogeology; 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; glaciofluvial sediments; glaciolacustrine sediments; Water supply; Phanerozoic; Cenozoic; Quaternary; Paleozoic; Ordovician; Cambrian |
| Illustrations | geoscientific 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 |
| Program | Groundwater Geoscience Aquifer Assessment & support to mapping |
| Released | 2018 07 05 |
| Abstract | The 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 ID | 308218 |
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