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Glaciofluvial systems of glaciated Canada: insights from the barren lands and areas of thick sediment cover in Canada

The barren lands of northern Canada display glacial landforms in exceptional detail, such as the vast esker networks, mapped since the first use of remote sensing (aerial photographs), and containing elements of dendritic and more parallel network organization. Recent field observations
along the trend of esker networks highlight zones of erosion and scour that parallel esker ridge lines. These erosion zones scoured 2-30 m deep, are ~0.2 to 5 km wide, spaced ~5'15 km apart, and are mapped sub-parallel for ~10 to >100 km in length. They have sharp to vague boundaries, carry
s-form and abrasion marks on exposed bedrock, show undulating longitudinal profiles and are referred to as glaciofluvial corridors. Glaciofluvial corridors appear to be equivalent to tunnel valleys /channels elsewhere in glacial landscapes mantled with thicker sediment. Comparison of glaciofluvial
corridors with inferred tunnel valleys in thicker sediment-mantled glaciated terrains in Canada is instructive where high-quality subsurface data exist. Recent aquifer characterization studies across Canada (e.g. Oak Ridges Moraine and prairie regions) have provided high-resolution geophysical and
continuous core data that add to our understanding of the style, character and timing of sediment fills within tunnel valleys, in addition to valley geometry and sediment architecture. Tunnel valleys can be eroded in rock, yet when eroded into sediment they are 10-200 m deep, ~0.2-10 km wide,
spaced 10-20 km apart (in places) and are ~10- >100 km long in sub-parallel to anabranched networks. Both glaciofluvial corridors and tunnel channels/valleys are well-defined systems within regional unconformities on the glaciated landscape.

Tunnel valleys and glaciofluvial corridors, though largely erosional landforms, also contain sediment fills of variable origin. Some contain mainly post-glacial deposits and little, if any, sediment fill associated with the formative events during glaciation. In contrast, fills in some tunnel
valleys can be complex and of multiple ages. High-quality core data reveal the presence of thick, coarse-grained, high-energy fills interpreted as waning-stage deposits related to the scoured surfaces of the tunnel valley.

The distribution, morphology, and sedimentology of glaciofluvial corridors and tunnel valleys lead to hypotheses of their formative processes and the possible spatial and temporal relationships between formation of corridors/ tunnel valleys/channels and eskers. Ultimately, these landscape elements
shed light on the glacial/deglacial dynamics, retreat styles and patterns, and the paleo-hydrology of the former Laurentide Ice sheet.

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