| The modeling approach used in this project was to use point data and 1D information (boreholes) to develop a 2D understanding, via a conceptual model and geological cross-sections, and then to interpolate the 2D cross-sections to create a 3D model. 3D modeling was carried out using the Gocad® software.
The sediment isopach map represents the distribution of the total thickness of the superficial formations covering the bedrock. It was created using the superficial formations map and the various primary input data covering the study area. The first step in its realization consisted of extracting bedrock outcrops and thin till (≤ 1m) regions from geological maps. Elsewhere, bedrock depth was calculated using only wells that reached the bedrock. The maximum thickness of the thin till zones after interpolation has been simplified to 1 meter.
The calculation of the thickness of each geological unit was carried out using Gocad® Discrete Smooth Interpolator (DSI) method. The different lithostratigraphic unit thickness maps have also been quantified with this interpolator. The proportion of SIH data was high, but the coverage of stratigraphic wells, geotechnical data, hydrogeological data and academic data resulted in a very realistic model of the geology of this area. A series of 16 stratigraphic cross-sections were integrated into the model to improve the geological realism of some valleys.
The estimation of the thickness of the deposits is constrained by the proximity of the rock. The thickness of the material varies regularly from a zero thickness near the elevated areas with bedrock outcrops to a maximum thickness in the center of the valleys.
The watershed has been discretized into a three-dimensional mesh, each cell having a resolution of 250 m x 250 m. This mesh is standard for data integration and despite the uncertainty of this type of spatial analysis; it appears sufficiently precise for regional hydrogeological models. |
| Primary input data used in the 3D modelling process: Outcrops; Academic studies (cross-sections); Well data (MTQ, MQQEFP (SIH), GSC, UQAM, private companies); Digital elevation model (DEM); Surficial geological map. |
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| In order to have fewer components in the 3D model and to simplify the modelling process, units with similar lithologic and hydrostratigraphic properties were group in single units. 9 final units resulting from this simplification are:
1) Organic sediments (O)
-Bog sediments (O)
2) Alluvial, glaciolacustrine and glaciomarine sediments - sandy gravelly (Ap, At, Ax, MGb, LGb, LGd)
-Alluvial sediments (includes Ap, At, Ax)
-Littoral and nearshore glaciomarine sands and gravels (MGb)
-Littoral and nearshore glaciolacustrine sediments (LGb, LGd)
3) Glaciomarine and glaciolacustrine sediments - silty clayey (MGa, LGa)
-Glaciomarine and marine clays and silts (MGa)
-Offshore glaciolacustrine sediments (LGa)
4) Glaciofluvial sediments (Gx, Gs, GxT)
-Glaciofluvial sediments (gravels and coarse sands; Gx, Gs, GxT )
5) Reworked glacial sediments (Tr, Trm)
-Reworked till (Tr, Trm)
6) Thin glacial sediments (Tm)
-Thin and discontinuous till layer, veneer (Tm)
7) Glacial sediments and old Quaternary sediments - silty clayey (Tc, Q)
-Continuous till layer, blanket (Tc)
-Old Quaternary formations (mainly fine glaciolacustrine sediments; varves or rhythmites; Q)
8) Old Quaternary sediments - sandy gravelly (Q/Gx, Q/LGd)
-Sandy old Quaternary formations (delta and buried glaciofluvial facies; Q/ LGd, Q/Gx)
9) Bedrock (R) |
| Primary input data used in the 3D modelling process: Outcrops; Academic studies (cross-sections); Well data (MTQ, MQQEFP (SIH), GSC, UQAM, private companies). |
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completed
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