Over the last decade helicopter electromagnetic (HEM) frequency and time domain (HFEM and HTEM) electrical resistivity surveys have been performed over buried glacial features that constitute major aquifers in different regions of the central North America. These surveys have been conducted to map geology, contaminants, and hydrogeology for groundwater studies. This paper summarizes the applications in four different glacial terrains. The HFEM systems applied in the surveys described here used frequencies from 400 to 140,000 Hz domain methods that, in electrically conductive areas may be limited to mapping depths less than 60 m. The HTEM survey described here used gate times from 50 microseconds to 5.4 milliseconds and can map to depths of more than100 m. The HEM surveys provide an insight into subsurface mapping capabilities and into the hydrogeologic framework of buried glacial valleys that host important regional aquifers.


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