Architecture of buried valleys in glaciated Canadian Prairie regions based on high resolution geophysical data

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Airborne electromagnetic and high resolution seismic geophysical data provide insight into complex buried valley geometry and internal sedimentary architecture of buried valleys in the Canadian Prairies. Buried valleys with an extent in excess of 20,000 km beneath the Canadian prairie landscape have been previously interpolated using borehole data; however, they provide only limited insight into the geometry and spatial relationships of these valleys. The collected high-quality geophysical datasets, a three-dimensional airborne electromagnetic survey and high resolution seismic profile data provide much greater resolution of buried valley geometry and internal sedimentary architecture of buried valleys. Several generations of valleys at different scales are identified. We interpret multiple erosion surfaces bounding thick diamicton sequences that fill the largest valleys; the youngest valleys are filled with variable sediment types. Three valley morphologies are identified and process origins inferred: 1) regional-scale, extensive, subaerial and pre/interglacial named α-type valley, 2) regional-scale, narrow and mainly proglacial, β-type valley and 3) local-scale, apparently discontinuous, subglacial, γ-type valley. Within the glacial sediment stratigraphy filling α-type valleys are thick diamicton sequences bounded by erosional surfaces. The β-type and γ-type valleys are filled with variable sediment types. The proglacial β valleys erode bedrock and also occur within the α-type valley fill. Conversely, the γ subglacial valleys are observed to crosscut other valleys and may be shallow and wide, or deep and narrow. The reported geophysical datasets supported by borehole data are able to map buried valleys in three-dimensions and hence identify the morphologic and stratigraphic relationships that permit improved constraints on process and erosional origin and fill of buried valleys. Results provide insight into the relationship between valleys formed as part of Tertiary fluvial erosion, multiple glaciations, and glaciofluvial events. These data provide significant insights on the distribution and character of potential groundwater reservoirs in Prairie regions.