CGRG Bibliography of Canadian Geomorphology
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Author : Ferbey, T.; Hickin, A.S.; Demchuk, T.E.; Barchyn, T.E.; and Levson, V.M.
Date : 2007.
Title : Effective ground geophysical methods for aggregate exploration in the lowlands of northeast British Columbia, Canada.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
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Abstract
The British Columbia Ministry of Energy, Mines and Petroleum Resources has been using innovative and non-intrusive ground-based geophysical methods for aggregate exploration including ground penetrating radar (GPR) and capacitively-coupled resistivity (CCR). The objective of these studies are to characterize subsurface sediments and assess areas identified as having potential to host granular material. Here, we present two case studies in which these approaches have been used successfully. Capacitively-coupled resistivity surveys were conducted using an OhmMapper™ instrument. Unlike traditional galvanic resistivity surveys, this CCR instrument collects nearly continuous data from a towed array composed of one transmitter and up to five receivers. By varying the configuration of this array, psuedosection depths of up to 10 m can be produced. This is a rapid and cost-effective method for collecting apparent resistivity data in topographically subdued lowland areas where dense vegetation, thick silt and clay-rich morainal and glaciolacustrine deposits, and high water tables dominate. In one study, conducted at the Kotcho East deposit (an aggregate deposit buried under up to five metres of diamict), CCR data were collected and compared to airborne electromagnetic (EM) data collected over the same deposit. The location and morphology of resistive features identified in the CCR data correlate well with those identified in the airborne EM dataset. There is, however, some variation in the details of this relationship. For example, CCR and EM apparent resistivity values for the same area vary, with maximum values being 810 and 65 ohm m, respectively. There is clear spatial correlation between these resistive features and the occurrence of sand and gravel. In another study, conducted at Scobie Ranch (near the confluence of Chowade and Halfway rivers), both GPR and a gridded CCR data were used to investigate the structure and lithofacies of abandoned meander channel and point-bar deposits. Profiles and planimetric maps of these ground geophysical data were produced and compared to aerial photographs and testpit data. The CCR profiles were combined with radar profiles, allowing the inference of lithofacies. Results indicate that clay, silt, sand, and gravel bodies can be differentiated in the profiles. Planimetric depth slices generated from inverted and gridded CCR data provide the lateral extent of the lithofacies to approximately 5 m depth. In this area, delineating the precise location of thick gravel bodies, with minimal overburden (silt and clay), will allow for more effective and efficient gravel extraction.
Bibliography of Canadian Geomorphology