Abstract

An airborne electromagnetic (AEM) survey using the Fugro RESOLVE™ system was conducted over a known, buried sand and gravel deposit in northeast British Columbia, Canada to determine its effectiveness for mapping similar deposits in the area. The rarity of gravel deposits in this region provides a significant economic constraint for developing oil and gas infrastructure. Topographic relief is minimal and the area is overlain by organic materials, clay-rich tills, and glaciolacustrine sediments. Traditional exploration methods, such as airphoto interpretation, are therefore ineffective for locating these buried deposits. The buried deposit appears as a resistivity high on the apparent resistivity maps, particularly the 115,000 Hz map. The resistivity high covers a larger area than that defined initially by test pitting. Trenching within this extended zone verified the presence of sand and gravel. Other resistive features in the region were identified by the survey and one of these was confirmed by recent test pitting to be a large sand and gravel occurrence. No surface indications of sand and gravel were evident over any of these occurrences. The cross sections indicated these sand and gravel occurrences have resistivity values greater than 70 ohm-m, often greater than 100 ohm-m, whereas the surrounding till has resistivity values between 5 and 15 ohm-m. The airborne survey proved to be a highly successful method of locating sand and gravel deposits in this area of British Columbia that could be widely used in other plains regions with similar geological settings.

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