THE ORANGEVILLE MORAINE PROJECT: FROM A SOUTHWESTERN ONTARIO QUATERNARY STRATIGRAPHIC FRAMEWORK TO A 3-D MODEL AND BEYOND
The southwest-dipping Paleozoic bedrock surface is characterized by deep re-entrant valleys that extend from the Niagara Escarpment and a series of shallower generally north east trending buried-bedrock valleys. Older tills, silt- and clay-rich glaciolacustrine and localized coarse-textured stratified sediments, likely deposited during ice retreat, are concentrated in the western and central portions of the area. Catfish Creek Till, deposited by the main (regional) Late Wisconsinan ice sheet, forms a key aquitard and an important stratigraphic marker across the region. A series of aquifers, including Orangeville Moraine glaciofluvial and subaquatic fan sediments, and fine-textured glaciolacustrine and diamicton aquitards were deposited during and following the break-up of the ice. Late glacial tills form the upper aquitard across much of the region and define the maximum extent of Huron-Georgian Bay and Erie-Ontario lobate ice advances.
Mapping the distribution and characteristics of regional-scale Quaternary sediment packages in the subsurface means it is now possible to model groundwater flow with increased accuracy. Buried-bedrock valleys, long viewed as potentially important sources of water, have been mapped in detail revealing knick points, plunge pools, disappearing streams and scarps that subdivide the valley systems. Derivative maps show areas with greatest groundwater recharge potential and vulnerability to surface contamination. Using a common stratigraphic framework allows the distribution, thickness and structural contours of units in contiguous 3-D project areas to be mapped quickly and easily as well as facilitating the generation of ‘super models’.