Abstract

A geodatabase of deformation structures with over 300 field observations and 53 attribute fields was compiled to assess the significance of soft-sediment deformation in Quaternary sediments in the Regional Municipality of Waterloo as they relate to existing depositional models and regional ice sheet dynamics. The regional distribution of morphologically diverse deformation structures is interpreted to reflect localized ice margin fluctuation as well as extensive gravity driven deformation associated with rapid sedimentation, sediment remobilization, or melting of buried or supporting ice in a glaciolacustrine setting. Deformation was often observed in coarse-grained sediment and included attenuated and chaotic bedding, shear folds, dikes, and reverse and normal faulting. It ranged in scale and complexity from an isolated centimetre-scale occurrence to entire metre-scale outcrops exhibiting multiple types of deformation at various scales. Some of the deformation was observed in clusters of several square kilometres, with deformation within the cluster being predominantly large scale and complex in coarse-grained sediments. These deformation structures can be attributed to simple shear and (or) compressional stress or stresses related to gravitational instability. Simple shear and compressional deformation are most common in localized areas of the moraine and in the surrounding till plains. In contrast, deformation related to gravitational instability is widespread and most common in the eastern half of the region. The coarse-grained texture and complex nature of deformation within clusters has implications for subsurface heterogeneity, and consequently, local groundwater flow regimes and contaminant transport at the well-field scale.

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