Airborne magnetic and radiometric survey, western Spirit Lake tectonic zone region, Iowa, Nebraska, South Dakota, and Minnesota, 2023-2024

This data release provides digital flight line data for a high-resolution airborne magnetic and radiometric survey over the western Spirit Lake tectonic zone region, covering parts of northwestern Iowa, northeastern Nebraska, southeastern South Dakota, and southwestern Minnesota. The airborne survey was funded by the Earth Mapping Resources Initiative. The survey was designed to meet complementary needs related to geologic mapping and characterization of mineral resource potential. A total of 274,148 line km of magnetic and radiometric data were acquired over an irregularly shaped area of ca. 99,500 km2. Data were collected from fixed-wing aircraft flown at a nominal terrain clearance of 100 meters (m) above topography along N-S flight lines spaced at 400-m intervals. Tie lines were flown in an E-W direction every 4,000 m. Data were collected by Sander Geophysics Limited and Dewberry under contract to the USGS using airplanes with a magnetometer mounted in a stinger and a fully calibrated gamma-ray spectrometer. The survey operated out of airports in O’Neill and Omaha, Nebraska, and Carroll, Iowa, from May of 2023 to August of 2024. Files that are available in this publication include flight line data for the magnetic survey, flight line data for the radiometric survey, and a report describing the survey parameters, field operations, quality control and data reduction procedures. A zip file is provided that contains the contractor's deliverable products that includes Geosoft databases and grids for the magnetic and radiometric survey and the report describing the survey and data reduction.