Glacial sediments are found across formerly glaciated regions across the world and host a variety of important resources, ranging from groundwater to hydrocarbons, aggregate material, and mineral deposits. In southern Ontario, Canada, thick successions (up to 200 m) of Quaternary glacial sediments are truncated by large valleys (>30km long, 2 to >8.5 km wide, and up to 200m deep) that formed subglacially and have characteristic morphology and infill stratigraphy. These valleys are interpreted as (a new class of) tunnel valleys and strongly affect groundwater resources and flow systems at local and regional scales. The overall context of the valleys is evaluated through an introduction to the study area, objectives, and background information on subglacial systems and geologic history of south-central Ontario (Chapter 1). Interpretation of valley genesis in Simcoe County is provided through an integrated, multi-faceted approach, involving: description of the morphology and sediment infill succession within the valleys from surficial mapping, sedimentological logging of continuously-cored boreholes, and geophysical surveys (Chapter 2); delineation and characterization of seismic architecture from high-resolution lake-based sub-bottom profiles in one of the valleys (Chapter 3); detailed site-scale field description of the internal characteristics of the regional Late Wisconsin till sheet in various subglacial settings (Niagara Escarpment, uplands, lowlands; Chapter 4); comparison of the characteristics of the subglacial bed within the study area to adjacent regions in southern Ontario (Chapter 5); and a synthesis of the major findings from all the different components of this investigation and suggestions for future work to shed further light on several questions that arise from this study (Chapter 6). Together, key data from these studies of tunnel valleys and related deposits – a near-continuous till sheet on the surface of uplands and along the flanks and floors of the tunnel valleys, multi-stage drumlinization of the till sheet following development of the tunnel valleys, variations in internal facies and physical properties within the till sheet in different subglacial settings, localized distribution of coarse-grained tunnel valley in-fill sediments, and gradational upward transitions from tunnel valley in-fills to fossiliferous proglacial lacustrine sediments – indicate multiple phases of subglacial meltwater, and direct subglacial, erosion and deformation contributed to the development of the valleys over a protracted time period during the Late Wisconsin. Landform and sediment associations within the valleys in Simcoe County and surrounding parts of the bed of the former Laurentide ice sheet in south-central Ontario, are inconsistent with previous conceptualizations involving the presence of large (>1000 km2) subglacial lakes and the storage and discharge of regional-scale subglacial meltwater sheetfloods followed by ice stagnation. This study provides new data and insight to help refine reconstructions and better understand the evolution of past ice dynamics and subglacial processes, evaluate competing theories of regional landscape evolution, and provide new conceptual and (hydro)stratigraphic frameworks for future hydrogeological investigations related to groundwater exploration and use. / Thesis / Doctor of Philosophy (PhD)

<p>This research utilizes sedimentology and geomatics to investigate relationships between sediment types, landforms and former glacial movement in southern Ontario, Canada. The research integrates qualitative field observations of sedimentary successions with quantitative assessment of landforms, specifically drumlins, using Geographic Information Systems (GIS). A detailed sedimentological analysis of late Quaternary sediments exposed in Vineland Quarry, Ontario identifies glaciolacustrine deposits which were subsequently overridden and deformed by glacial ice. The gradual transition from undisturbed, laminated sediment to increasingly deformed sediment and structureless diamict exposed at Vineland is consistent with theoretical models of subglacial deformation and suggests that the succession records a single episode of ice advance across the Vineland region.</p> <p>The second component of this research is presented within two research papers that explore a computational methodology within GIS which allows identification of drumlins and their morphological characteristics from existing topographic digital data. The two studies examine the form and spatial distribution of drumlins within the Arran, Galt and Guelph drumlin fields and from a portion of the Peterborough drumlin field. Drumlins and their morphological characteristics, such as elongation ratio and long axis orientation, are identified and documented using a computer-based process that allows direct comparison of forms within and between individual drumlin fields. The computer-based spatial analysis shows that drumlins are not randomly distributed across the regions, but show distinct patterns of clustering. Drumlins with particular morphological characteristics also show a clustered distribution that may be related to spatial changes in sediment thickness, duration of ice cover, and the direction of ice movement. The ability to consistently identify and characterize drumlin morphology and distribution allows objective and systematic comparison of these landforms both within and between drumlin fields and will enhance understanding of the spatial controls on the development of these enigmatic landforms.</p> / Doctor of Philosophy (PhD)