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TitleGeological and hydrogeological models of the 'Yonge Street aquifer', south-central Ontario
AuthorGerber, R; Hoylsh, S; Russell, H A J; Sharpe, D R
SourceIAH-CNC 2015 Waterloo, abstracts; 2015.
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20150064
PublisherIAH
MeetingIAH-CNC 2015 Waterloo; Waterloo; CA; October 27-30, 2015
Documentbook
Lang.English
Mediapaper
ProvinceOntario
NTS40P/08; 40P/09
AreaBrantford; Cambridge; Guelph
Lat/Long WENS-80.5000 -80.0000 43.7500 43.2500
Subjectsstratigraphy; sedimentology; hydrogeology; glacial deposits; moraines; aquifers; groundwater; lithology; sands; clays; silts; gravels; depositional models; depositional environment; stratigraphic analyses; stratigraphic correlations; pits; cores; boreholes; modelling; Paris Moraine; Galt Moraine; St. George Aquifer; Grand River; Blue Spring Creek; Quaternary
Illustrationsgeological sketch maps; stratigraphic correlations
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
AbstractIn the Aurora, Newmarket and Queensville areas of the Greater Toronto Area, south-central Ontario, municipal water supply is obtained from the 'Yonge Street aquifer' (YSA), an informal name long used to describe relatively deep sand and gravel deposits. These deposits were previously described as discontinuous, perhaps channelized and possibly associated with buried bedrock valleys, largely interpreted from data at a few municipal well fields. Despite much historical and recent geological and hydrogeological work, including numerical groundwater flow modelling, the fundamental geological and hydrogeological framework (i.e. conceptual model) for the YSA has not been clearly developed and documented.
Based on high-quality geophysical and geological data (seismic profiles, continuously'cored, sedimentologically-logged boreholes, downhole geophysics, geological mapping and 3-D modeling) revised conceptual geological and hydrogeological models of the area are presented. The data reveal a sedimentary succession of ~140 m thickness that is truncated by a number of erosional unconformities characterized by deeply incised channels, locally extending to bedrock, with a ~NS to NE-SW orientation, both beneath and above the regional Newmarket Till stratigraphic marker. Channels may occur stratigraphically stacked and nested with local erosion of the Newmarket Till. Core and seismic data permit identification of channelized Thorncliffe Fm. sediment flanked by older sand and mud Scarborough Fm. equivalents. The Thorncliffe Fm. consists of fining upward successions from coarse gravel to rhythmically bedded muds interpreted to be deposited within a channel-esker-subaqueous fan complex. The YSA aquifer is one component of a system of similar deposits recognized across the region beneath drumlinized Newmarket Till.
The accompanying hydrogeological model benefits from a strong conceptual understanding of vertical and lateral facies changes in the Thorncliffe Fm. depositional model. The subaqueous fan gravel-sand-mud, fining-upward facies succession provides a capping aquitard to YSA, in addition to the overlying Newmarket Till aquitard. Lateral coarse to fine facies transitions are very rapid perpendicular to paleoflow and explain dry wells drilled near YSA municipal wells. Facies transitions are much longer along paleoflow, as supported by pumping tests in a similar aquifer system north of Markham which have high-yield hydraulic connection of ~1-10 kms.
The conceptual models documented in this paper are critical to guiding groundwater exploration and management. Paramount to improved knowledge is collection of high-quality subsurface data that aids in developing a geological framework that represents the sedimentary system of the basin and its internal flow systems.
Summary(Plain Language Summary, not published)
Documents the sedimentology and hydrostratigraphic context of the Yonge Street Aquifer. Based on this framework hydraulic data is assessed to provide a characterization of the aquifer.
GEOSCAN ID296501