CGRG Bibliography of Canadian Geomorphology
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Author : Gao, C.; Shirota, J.; Kelly, R.I.; Brunton, F.R.; and van Haaften, S.
Date : 2006.
Title : Project Unit 05-013. Bedrock topography and overburden thickness mapping, southern Ontario.
Publication : Summary of Field Work and Other Activities 2006, Ontario Geological Survey.Queen's Printer for Ontario.
Issue : Open File Report 6192.
Page(s) : 34-1 to 34-10.
Abstract
The following article outlines protocols and a methodology developed by the Ontario Geological Survey (OGS) to generate digital regional bedrock elevation and overburden thickness maps for southern Ontario. Advances in data storage and retrieval of the extensive petroleum, engineering and water well records as well as geological observations acquired over the last 50 years have made updated maps both timely and possible. Using ESRI® ArcGIS® analysis functions such as kriging, these data can be integrated and analyzed to generate bedrock topography maps. The approximate thickness of the Quaternary sediments is determined by subtracting the bedrock elevation surface from the provincial digital elevation model (DEM). Bedrock elevation and drift thickness information is important in bedrock aggregate resource assessments, groundwater studies, geotechnical work and other land-use applications. For instance, Ontario’s current aggregate resources inventory mapping program, which was initiated in the late 1970s, assesses the aggregate resources for both naturally formed sand and gravels, and crushed stone derived from bedrock (Ontario Mineral Aggregate Working Party 1977; Cowan 1978; Kelly and Rowell 1995; Baker 2003). The resultant Aggregate Resources Inventory Paper (ARIP) publications form important components in municipal land-use planning and resource management to ensure that adequate resources of mineral aggregate remain available for future use. A key component of an ARIP is a bedrock resources map outlining areas of thin surficial sediment cover where bedrock aggregate resources can be obtained at lower cost. Since 2003, several pilot projects have been undertaken to develop drift thickness mapping for mineral aggregate and groundwater studies across southern Ontario (van Haaften et al. 2004; Gao et al. 2005; Shirota, Brunton and Kelly 2005). Feedback from users of the resultant maps has led to many improvements to the methodology. As a result, it was decided to expand the drift thickness mapping methodology to generate the bedrock topography and overburden thickness maps of southern Ontario. The bedrock of southern Ontario comprises both Paleozoic sedimentary and Precambrian metamorphic and igneous rocks (Ontario Geological Survey 1991; Johnson et al. 1992). Glaciations during the Quaternary period of the recent geological past resulted in both the physical erosion and sculpting of the bedrock surface and subsequent burial of much of the bedrock by varied thicknesses of till, clay, sand and gravel deposits (Barnett, Cowan and Henry 1991; Barnett 1992; Ontario Geological Survey 2003). In comparison with previous bedrock topography studies (Karrow 1973; Chapman and Putnam 1984; Flint and Lolcama 1986; Eyles, Boyce and Mohajer 1993; Eyles et al. 1997; Brennand et al. 1998; Edgecombe 1999; Eyles 2002), additional quality control measures were undertaken so that problematic data were able to be tracked and eliminated. As such, this new approach has enabled better delineation of the bedrock topography, in particular, the regional extent of significant buried bedrock valleys across southwestern Ontario.
Bibliography of Canadian Geomorphology