THREE-DIMENSIONAL SUBSURFACE MAPPING OF QUATERNARY SEDIMENTS INFILLING PARTS OF THE DUNDAS VALLEY, HAMILTON, ONTARIO

The Dundas Valley of the Hamilton-Wentworth region of southern Ontario forms a prominent west-east re-entrant in Paleozoic bedrock of the Niagara Escarpment and is infilled with up to 180m of Quaternary sediment. Although the sedimentary infill of the Dundas Valley is poorly understood, borehole records indicate that the valley contains stacked units of coarse and fine-grained sediments of glacial, fluvial and lacustrine origin. Coarse-grained units form local and regional aquifers that supply surface water bodies such as Cootes Paradise and Hamilton Harbour. The Dundas Valley hosts a densely populated and heavily urbanized region with serious concerns regarding contamination of ground and surface water. The Hamilton region is now the focus of a major groundwater resources inventory project due to a pressing need to improve understanding of the three-dimensional (3D) subsurface distribution of sediments, particularly aquifers, within the Dundas Valley.

This poster describes the initial results from the compilation and modeling of subsurface geological data obtained from waterwell and borehole records, engineering and construction reports from the Hamilton region. RockWorks 2002 was used to model and create images describing the subsurface stratigraphy of the region. The images show the irregular topography of the underlying Queenston Shale bedrock and the geometries of overlying sediment units that include clays and silty clays, sands and gravels and silty sands. Clays and silty clays record either glaciolacustrine depositional conditions or subglacial reworking of previously deposited lacustrine sediments formed during the final stages of Late Wisconsin glacial occupation of the Lake Ontario basin or during the early stages of postglacial Lake Iroquois. Overlying coarse sands and gravels formed in high energy conditions are probably associated with shoreline environments of Lake Iroquois. The uppermost sedimentary units mapped consist of silts and silty sands formed in lagoonal environments created at the western end of Lake Iroquois by the growth of shoreline bars.

The 3D images of subsurface sediment characteristics and distributions created for the Hamilton region will help identify and delineate major aquifers and aquitards, and may be used for future water resource and remediation planning.