|Titre||Bottoms up: developing a new bedrock surface for the Niagara Peninsula|
|Télécharger||Téléchargement (publication entière) |
|Auteur||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; par Russell, H A J; Ford, D;
Priebe, E H; Holysh, S; Commission géologique du Canada, Dossier public 8363, 2018 p. 6, https://doi.org/10.4095/306489 (Accès ouvert)|
|Éditeur||Ressources naturelles Canada|
|Réunion||Regional-Scale Groundwater Geoscience in Southern Ontario: Open House; Guelph; CA; février 28 - mars 1, 2018|
|Media||en ligne; numérique|
|Référence reliée||Cette publication est contenue dans 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, Commission géologique du Canada,
Dossier public 8363|
|SNRC||30L/13; 30L/14; 30L/15; 30M/02; 30M/03; 30M/04; 30M/06|
|Lat/Long OENS|| -80.0000 -78.7500 43.5833 42.7500|
|Sujets||topographie du substratum rocheux; établissement de modèles; levés géophysiques; levés gravimétriques, sol; levés de reflexion sismiques; diagraphie géophysique; puits d'observation; trous de mine;
échantillons carrotés; épaisseur de la couverture meuble; analyses stratigraphiques; escarpements; vallées enfouies; logiciel; géologie régional; géologie des dépôts meubles/géomorphologie; géophysique; Phanérozoïque; Cénozoïque; Quaternaire;
|Programme||Géoscience des eaux souterraines, Aquifer Assessment & support to mapping|
|Diffusé||2018 02 16|
|Résumé||(disponible en anglais seulement)|
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.
Five shallow, 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.