Airborne magnetic and radiometric survey of the Wet Mountains and surrounding region, Custer and Fremont Counties, south-central Colorado, 2021

This data release provides digital flight-line and gridded data for a high-resolution airborne magnetic and radiometric survey over the region surrounding the Wet Mountains of southern Colorado, including parts of Custer and Fremont Counties. Data for this survey were collected by Sander Geophysics Limited International (SGL) under contract with the USGS. The survey was flown in June and July of 2021 using a helicopter equipped with a magnetometer mounted in a stinger extending from the nose of the aircraft and a gamma-ray spectrometer stowed onboard. The helicopter pilots followed pre-planned flight paths in a grid-like pattern, with east-west lines spaced 150 meters apart and north-south lines spaced 1,000 meters apart. A terrain clearance of 80 meters above ground could be realized in areas of low relief to maximize detection of gamma-rays, but higher clearances, as much as 200-500 meters, were required over rugged terrain and populated areas for safety reasons. A total of 17,032 kilometers were flown along the lines, covering a 2,200 square-kilometer irregular area. SGL performed extensive data processing after completion of flying and delivered the final data and report in February 2022.