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USGS Mineral Resources: Magnetic anomaly maps and data for North America
From the site: "Airborne measurement of the earth's magnetic field over all of North America provides gridded data describing the magnetic anomaly caused by variations in earth... -
Precambrian basement structure map United States
The Precambrian basement rocks of the continental United States are largely covered by younger sedimentary and volcanic rocks, and the availability of updated aeromagnetic data...