Airborne time-domain electromagnetic data for mapping and characterization of the Spiritwood Valley aquifer, Manitoba, Canada

Abstract

A helicopter-borne, time-domain electromagnetic survey was flown over a 1062 km2 area of the Spiritwood Valley in southern Manitoba. The objective was to test the effectiveness of commer-cial, airborne, time-domain electromagnetics for mapping and characterizing buried valley aquifers in the Canadian Prairies. The preliminary data exhibit rich information content, but show some levelling bias and potential limitations of dynamic range or bandwidth. Time slices of the magnetic field decay clearly map the broader Spiritwood Valley in addition to a continuous, incised valley along the broader valley bottom. The data indicate a complex valley morphology with nested scales of valleys, including at least three dis-tinct valley features and multiple possible tributaries. Time-domain electromagnetic response magnitude and decay rates indicate that the fill material within the incised valleys is more resistive than the broader valley fill, consistent with an interpretation of sand and gravel. The electromagnetic data are in excellent agreement with seismic reflection data collected inside the survey block. Further ground-based investiga-tion and data integration is planned. These preliminary results suggest that time-domain electromagnetic surveys have the potential for mapping buried valley aquifers in the Canadian Prairies in far greater detail that any previous techniques.