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.
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Research Article|
July 05, 2018
Conceptual hydrogeological model of the Yonge Street Aquifer, south-central Ontario: a glaciofluvial channel–fan setting1
Richard E. Gerber;
Richard E. Gerber
a
Oak Ridges Moraine Groundwater Program, Toronto, ON, Canada.
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David R. Sharpe;
David R. Sharpe
b
Geological Survey of Canada, Ottawa, ON, Canada.
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Hazen A.J. Russell;
Hazen A.J. Russell
b
Geological Survey of Canada, Ottawa, ON, Canada.
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Steve Holysh;
Steve Holysh
a
Oak Ridges Moraine Groundwater Program, Toronto, ON, Canada.
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Esmaeil Khazaei
Esmaeil Khazaei
c
Toronto and Region Conservation Auihority, Toronto, Ontario, Canada.
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Canadian Journal of Earth Sciences (2018) 55 (7): 730–767.
Article history
received:
04 Aug 2017
accepted:
13 Apr 2018
first online:
12 Jul 2018
Citation
Richard E. Gerber, David R. Sharpe, Hazen A.J. Russell, Steve Holysh, Esmaeil Khazaei; Conceptual hydrogeological model of the Yonge Street Aquifer, south-central Ontario: a glaciofluvial channel–fan setting. Canadian Journal of Earth Sciences 2018;; 55 (7): 730–767. doi: https://doi.org/10.1139/cjes-2017-0172
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Index Terms/Descriptors
- aquifers
- aquitards
- bedrock
- Canada
- Cenozoic
- Eastern Canada
- fluvial environment
- geophysical methods
- geophysical profiles
- geophysical surveys
- glacial environment
- glaciofluvial environment
- ground water
- hydrostratigraphy
- lithostratigraphy
- Oak Ridges Moraine
- Ontario
- paleochannels
- paleoenvironment
- Pleistocene
- pump tests
- Quaternary
- seismic methods
- seismic profiles
- seismic stratigraphy
- surveys
- water table
- Halton Till
- Newmarket Till
- Thorncliffe Formation
- Yonge Street Aquifer
Latitude & Longitude
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