Bedrock Topography and Sedimentary Infill of the Dundas Valley, Hamilton, Ontario

Abstract

<p>The Dundas Valley of the Hamilton-Wentworth Region forms a prominent west-east re-entrant in the Niagara Escarpment. However as a result of a thick overburden cover little is known of the subsurface geology. In an attempt to define the buried bedrock topography and overlying stratigraphy of the Dundas Valley, a detailed multi-parameter geophysical and sedimentological study was conducted.</p> <p>New bedrock topography maps based on recently released digital water well data provides details of the regional bedrock morphology, of the western termination of the Dundas Valley, and of surface lineaments on the bedrock surface. Multi-channel seismic reflection profiles provide detailed imaging of the bedrock surface and allow identification of an west-east trending normal fault in bedrock, which shows up to 25m of vertical offset. The coincidence of normal faults and lineaments on the bedrock surface suggests that the lineaments are fault controlled. Differential elevations of the bedrock surface on the north and south sides of the valley also suggests that the Dundas Valley may parallel a normal fault. In addition, the axis of the Dundas Valley coincides with a well defined aeromagnetic anomaly which delineates a deep-seated fault in the Precambrian basement (the Hamilton-Presqu'ile Fault). It is, therefore, proposed that original planes of weakness in the bedrock were probably exploited by glacial and fluvial erosional processes to produce the bedrock form of the Dundas Valley observed today.</p> <p>Infilling of the valley by Late Pleistocene glaciolacustrine deposits has produced an infill which is dominated by fine-grained lacustrine/glaciolacustrine deposits and coarser-grained fluvial/nearshore deposits. Coarse-grained units have the potential to act as groundwater and contaminant migration pathways. A better understanding of the detailed nature of the infill sediments is necessary to precisely identify and delineate these subsurface pathways.</p>