|Title||Bottoms up: developing a new bedrock surface for the Niagara Peninsula|
|Download||Download (whole publication) |
|Author||Burt, A K; Biswas, S; Rainsford, D; Dietiker, B; Pugin, A; Crow, H|
|Source||Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario geoscientists open house; by Russell, H A J; Ford, D; Priebe,
E H; Holysh, S; Geological Survey of Canada, Open File 8363, 2018 p. 6, https://doi.org/10.4095/306489 (Open Access)|
|Publisher||Natural Resources Canada|
|Meeting||Regional-Scale Groundwater Geoscience in Southern Ontario: Open House; Guelph; CA; February 28 - March 1, 2018|
|Related||This publication is contained in Russell, H A J; Ford, D;
Priebe, E H; Holysh, S; (2018). Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario geoscientists open house, Geological Survey of Canada, Open File
|NTS||30L/13; 30L/14; 30L/15; 30M/02; 30M/03; 30M/04; 30M/06|
|Lat/Long WENS|| -80.0000 -78.7500 43.5833 42.7500|
|Subjects||regional geology; surficial geology/geomorphology; geophysics; bedrock topography; modelling; geophysical surveys; gravity surveys, ground; seismic reflection surveys; geophysical logging; observation
wells; boreholes; core samples; overburden thickness; stratigraphic analyses; escarpments; buried valleys; software; Datamine Studio; Erigan channel; 3D modelling; geological mapping techniques; Phanerozoic; Cenozoic; Quaternary; Paleozoic|
|Program||Aquifer Assessment & support to mapping, Groundwater Geoscience|
|Released||2018 02 16|
|Abstract||The Niagara Peninsula three-dimensional (3-D) sediment mapping project was initiated in 2013 with the primary goal of constructing a model of regional-scale Quaternary deposits that form both regional
and local aquifers and aquitards between Port Dover in the southwest, the Regional Municipality of Waterloo in the northwest and the Niagara River in the east. To date, the primary focus of the project has been on data acquisition. |
high-resolution seismic reflection lines, ranging from 4.5 to 21.5 km in length, were acquired by the Geological Survey of Canada's (GSC) Near Surface Geophysics Section to determine whether multiple thalwegs exist within the buried Erigan channel,
to delineate the lateral extent and geometry of gravel beds observed during drilling and to provide insight into late-glacial moraine systems. Downhole geophysical logging was conducted in monitoring wells to investigate chemical and physical
properties of the sediments, and to verify the conversion of seismic reflection time sections to depths..
A 6828 station ground gravity survey was conducted along selected roads and highways at a nominal spacing of 100 m. The calculated gravity
residuals were used to identify buried-bedrock valleys and guide subsequent drilling. The survey was effective in identifying deeply incised valleys, such as St. Davids and the northern end of the Erigan, but less definitive where valleys broaden and
the deep regional and shallow residual components of the gravity are not as easily separated.
A total of 99 continuously cored boreholes with a combined length of 3192 m, 29 of which have been converted into monitoring wells, have been drilled
for this project. The borehole data is augmented by 130 exposures, soil probe and hand-auger cores and extensive legacy datasets (water well records, oil and gas records, geotechnical records, published geological reports and archived field notes).
A key first step in the 3-D modelling process is to generate a high-quality bedrock topographic surface that forms the foundation layer for the overlying sediment model. The surface is interpolated using Datamine Studio® software after manually
digitizing 3-D points identifying the top of rock onto the new and legacy borehole traces. Additional points were digitized adjacent to, or below, the borehole traces in order to refine the geometry of the surface and reduce potential effects of
clustered data points. By modelling the gravity results using representative density values for the Quaternary and bedrock layers, and integrating with interpretations from seismic studies in the area, it is possible to further constrain the shape of
the bedrock surface.
The resulting surface shows southward-dipping bedrock separated by the prominent features of the Niagara and Onondaga escarpments. Deep and narrow re-entrant valleys bisect the resistant escarpments, becoming wider where they
cross softer formations.