Master of Arts (MA)
Geography & Environmental Studies
Faculty of Arts
The Dundalk Till Plain in southwestern Ontario is crossed by five “esker-like” ridges, believed to have been formed simultaneously during the early stage of the mid-Port Burce Stadial. The three middle ridges are the focus of this research, with each ridge having a different topographic form, but the length of, and distance between, ridges are similar. Occurrences of differing depositional structures and the presence of deformational structures over short lateral and vertical distances reveal the complexity of processes involved. The dominant primary sedimentary structures are large-scale tabular cross-beds. Many individual cross-beds are composed of poorly sorted, matrix-supported gravels. High variability in the type and characteristics of depositional structures over a short lateral distance is common within sections. The majority of deformational structures consist of high angle reverse faults and normal faults, associated with ice-contact support. Other deformational structures include a lateral series of “V-shaped” wedges which are exposed in two of the “esker ridges”. Thin “till-like” units were observed in several sections as well as continuous units of the Tavistock Till and Elma Till, the latter being a new easternmost, known location of this till. Small-scale deformation is seen in sediments immediately above and below several of these tills and “till-like” units. From the location of the tills and the nature of the structures, revisions to the local stratigraphic record were suggested which place the formation of the eastern two eskers during the early phase of the mid-Port Bruce Stadial. The western ridge was formed later, by ice associated with the Tavistock Till. The summation of field observations of depositional and deformational structures, paleocurrents and laboratory results, indicate that the deposits are eskers and not interlobate moraine. The interpretation of these results and observations indicate that the western ridge was formed separately, the other two ridges having been created early by similar processes.
Parish, John D., "Depositional and deformational structures in three 'esker-like' ridges, southwestern Ontario" (1990). Theses and Dissertations (Comprehensive). 356.