The Magnetic Anomaly Map of North America; A new tool for regional geologic mapping
William J. Hinze, Peter J. Hood, 1989. "The Magnetic Anomaly Map of North America; A new tool for regional geologic mapping", The Geology of North America—An Overview, Albert W. Bally, Allison R. Palmer
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Although the charting of anomalous variations in the Earth′s magnetic field to aid in the mapping of the Earth′s crust has been practiced for over a century, the development of aeromagnetic surveying technology has made it possible in recent decades to conduct surveys of extensive regions efficiently and precisely. These improvements in surveying instrumentation, procedures, and data processing made it possible to move from magnetic “anomaly hunting” to the preparation of regional total field contour maps. Aeromagnetic surveys have been conducted over limited areas for specific geologic objectives, with little attention paid to the possibility of compositing individual surveys into regional, small-scale maps for the study of continental-scale geologic features. However, interpretation of compilations of simplified near surface, aeromagnetic anomaly maps (e.g., MacLaren and Charbonneau, 1968), and high-level, broadly spaced profile surveys (e.g., Zietz and others, 1969; Sexton and others, 1982) has shown that small-scale, low-resolution magnetic anomaly maps of extensive regions can be very useful in mapping continental scale geologic features.
Since the mid-1940s, airborne magnetic surveys have been conducted over vast regions of North America. The public availability of many of these surveys led to the preparation of national maps by Canada and the United States. The first 1:5,000,000 scale colored magnetic anomaly map of Canada (Morley and tohers, 1968) was prepared with hand-compilation techniques by the Geological Survey of Canada (GSC). Subsequent editions of the map have provided greater coverage and improved detail, leading to the fifth edition (Dods and others, 1987), which was produced by machine-compilation of digital data.