The 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.
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Research Article|
April 20, 2018
Geological framework of the Laurentian trough aquifer system, southern Ontario1
David R. Sharpe;
David R. Sharpe
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
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André J.-M. Pugin;
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
Corresponding author: D.R. Sharpe (email: [email protected]).
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Hazen A.J. Russell
Hazen A.J. Russell
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
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David R. Sharpe
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
Hazen A.J. Russell
Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
Corresponding author: D.R. Sharpe (email: [email protected]).
Publisher: Canadian Science Publishing
Received:
19 May 2017
Accepted:
13 Apr 2018
First Online:
12 Jul 2018
Online ISSN: 1480-3313
Print ISSN: 0008-4077
Published by NRC Research Press
Canadian Journal of Earth Sciences (2018) 55 (7): 677–708.
Article history
Received:
19 May 2017
Accepted:
13 Apr 2018
First Online:
12 Jul 2018
Citation
David R. Sharpe, André J.-M. Pugin, Hazen A.J. Russell; Geological framework of the Laurentian trough aquifer system, southern Ontario. Canadian Journal of Earth Sciences 2018;; 55 (7): 677–708. doi: https://doi.org/10.1139/cjes-2017-0113
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Index Terms/Descriptors
- aquifers
- bedrock
- buried valleys
- Canada
- Cenozoic
- cores
- Eastern Canada
- geophysical methods
- geophysical profiles
- geophysical surveys
- glacial environment
- glaciolacustrine environment
- ground water
- hydrostratigraphy
- lacustrine environment
- lithostratigraphy
- Oak Ridges Moraine
- Ontario
- paleoenvironment
- Pleistocene
- Quaternary
- Scarborough Formation
- sediments
- seismic methods
- seismic profiles
- seismic stratigraphy
- surveys
- Laurentian Trough
- Sunnybrook Till
- Don Formation
- Pottery Road Formation
- Newmarket Till
- Thorncliffe Formation
Latitude & Longitude
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