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TitleGeological framework of the Laurentian Trough aquifer system, southern Ontario
AuthorSharpe, D R; Pugin, A J -M; Russell, H A J
SourceQuaternary geology of southern Ontario and applications to hydrogeology/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, issue 7, 2018 p. 677-708, https://doi.org/10.1139/cjes-2017-0113
Year2018
Alt SeriesNatural Resources Canada, Contribution Series 20170007
PublisherCanadian Science Publishing
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
Released2018 04 20
AbstractThe Laurentian trough (LT), a depression >100 km long, >3000 km2 in area, and 100 m deep at the base of the Niagara Escarpment, extends from within Georgian Bay to Lake Ontario. It has a complex erosional history and is filled and buried by up to 200 m of interglacial and glacial sediment. The primary depression fronts a cuesta landscape and is attributed to differential erosion by fluvial, glacial, and glaciofluvial processes, exposing Ordovician rocks along the Canadian Shield margin. The fill succession includes sediments from the last two glacial periods (Illinoian, Wisconsinan) and the intervening interglacial time (Sangamonian), a poorly dated succession with at least three regional unconformities. A subaerial (interglacial, Don Formation) unconformity relates to low base level mainly preserved in lows of the LT, succeeded by a long period of rising water levels and glaciolacustrine conditions as ice advanced into the Lake Ontario basin. A second unconformity, within the Thorncliffe Formation, is the result of rapid channel erosion to bedrock, forming an ~north-south network filled with coarse-grained glaciofluvial, transitional to fine-grained glaciolacustrine subaqueous fan sediment. The overlying drumlinized Newmarket Till, up to 50 m thick, is a distinct regional unit with a planar to undulating base. A third unconformity event eroded Newmarket Till, locally truncating it and underlying sediment to bedrock. Three younger sediment packages, Oak Ridges Moraine (channel and ridge sediment), Halton, and glaciolacustrine overlie this erosion surface. Significant regional aquifers are hosted within the LT. Upper Thorncliffe Formation sediments, north-south glaciofluvial channel-fan aquifers, are protected by overlying mud and Newmarket Till aquitards. Similarly, Oak Ridges Moraine sediments comprise a north-south array of glaciofluvial channel-fans and east-west fan aquifers, locally covered by silt-clay rhythmite and till aquitards.
Summary(Plain Language Summary, not published)
Buried valleys are important sources of groundwater resources in glaciated terrain such as the study area, a large region east of the Niagara Escarpment, south of Georgian Bay and north of Lake Ontario. Because glacial-age sediments are thick in this area (up to 200 m thick), the groundwater resources are poorly known in this very populated area despite considerable study under the Ontario Source Water Protection program and the Clean Water Act. Hence, this report provides are regional geological and hydrogeological framework based on new and existed high-quality data that provide a defensible basis for ongoing groundwater resource management.
GEOSCAN ID300262