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TitleNew insights on regional stratigraphy and hydrogeology based on surficial and subsurface sediment mapping in Simcoe County, southern Ontario
DownloadDownload (whole publication)
AuthorMulligan, R P M
SourceRegional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario open house; by Russell, H A J; Ford, D; Priebe, E H; Geological Survey of Canada, Open File 8212, 2017 p. 27,
PublisherNatural Resources Canada
MeetingOntario Geological Survey and Geological Survey of Canada groundwater geoscience open house; Guelph; CA; March 1-2, 2017
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Russell, H A J; Ford, D; Priebe, E H; (2017). Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario open house, Geological Survey of Canada, Open File 8212
File formatpdf
NTS31D/05; 31D/11; 31D/12; 31D/13; 31D/14; 41A/07; 41A/08; 41A/09; 41A/10; 41A/16
AreaSimcoe County; Lake Simcoe
Lat/Long WENS -80.7500 -79.0000 45.0000 44.2500
Subjectshydrogeology; stratigraphy; surficial geology/geomorphology; groundwater; aquifers; groundwater resources; resource management; hydrostratigraphic units; groundwater regimes; groundwater flow; glacial deposits; tills; glaciolacustrine deposits; sands; gravels; silts; clays; boreholes; grain size analyses; topography; postglacial deposits; erosion; Thorncliffe Formation; Newmarket Till; diamicton; water supply; aquitards; Phanerozoic; Cenozoic; Quaternary
Natural Resources Canada Library - Ottawa (Earth Sciences)
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
Released2017 02 22
AbstractThe integration of detailed field mapping of surficial sediments and landforms with information obtained from 14 continuously-cored boreholes are providing key insights into the character and distribution of major sediment packages that form regionally significant hydrostratigraphic units that control groundwater flow systems within Simcoe County.
Six major sediment packages are observed, forming successions >160 m thick. A dense sandy till (LCT) overlies the bedrock at most locations in the study area. This till is locally overlain by glaciolacustrine deposits (LGL), which are generally fine-grained although sandy facies are encountered and gravel deposits forming units up to 48 m thick have been observed in two boreholes to date. A fine-grained till (LFT) overlies the lower glaciolacustrine deposits forming a continuous, highly undulating marker bed in the subsurface. The upper surface of the till shows evidence of subaerial weathering at higher elevations (> 170m asl). It is overlain by a fining-upward succession of predominantly sand with lesser gravel and local accumulations of silt and clay-rich diamictons (TF), tentatively assigned to the Thorncliffe Formation. These deposits are overlain by a dense silty sand to sand till (NT) ranging from 2 to 30 m thick and correlative with the Newmarket Till. Particle size analysis of this till shows a progressive coarsening northward. Significant topographic variation in the Newmarket Till is observed across the study area - its upper surface ranging from 150 to 310 m asl. This highly undulating unit imparts a strong control on the character of overlying deposits. Where the till is found at lower elevations, laminated silts and clays form the bulk of the deglacial succession (LA). At higher elevations (>230 m asl), sands and gravels dominate.
The lower parts of the succession (LCT, LGL, LFT) do not commonly host significant aquifers. However, the bedrock interface aquifers can meet the demands for rural domestic use, and where the thick gravel deposits are encountered, significant groundwater resources may be present, especially given its occurrence at several tens of meters below modern Georgian Bay. Within the study area, the Thorncliffe Formation deposits form a regionally significant confined aquifer. It occurs regionally beneath both uplands and lowlands and, in many areas, artesian conditions are present. The Newmarket Till forms a regionally significant leaky aquitard, but coarser textures observed in this till in the north appear to significantly decrease its competency as an aquitard. Deglacial sediments generally form thick aquitards in low-lying areas but may form unconfined aquifers at higher elevations. Additionally, erosion of the Newmarket Till during deglaciation has led to preferential groundwater flow path that govern groundwater seepages and create large piping features. Geophysical studies have been carried out to better constrain the architecture of major sediment packages in the subsurface and to characterize the physical properties of the major stratigraphic units. In-situ hydrogeologic tests are planned in order to provide preliminary analysis of aquifer capacities and assess hydraulic connection of aquifers in the region.