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Editor: In the public interest and in accordance with the Federal Aviation Administration regulations, the USGS is announcing this low-level airborne project. Your assistance in informing the local communities is appreciated.

The new airborne geophysical survey data will be collected using an airplane and will fly over parts of northwest Iowa, northeast Nebraska, southwest Minnesota, and southeast South Dakota, weather permitting. The survey will begin in mid-May and be completed in about four to six months.

Image shows a map of the central United States with the survey area shown as a blue polygon
The Spirit Lake tectonic zone survey will cover a broad swath of land, including parts of Iowa, Minnesota, Nebraska and South Dakota.

The geophysical survey will focus on the buried Spirit Lake tectonic zone that is centered in the area between Sioux Falls, South Dakota, and Omaha, Nebraska. The region is thought to have potential for critical mineral deposits buried in the ancient Precambrian rocks deep beneath the glacial deposits and sedimentary rocks exposed near the surface. The purpose of the geophysical survey is to better map the ancient Precambrian rocks at depth. The region was chosen in collaboration with the Iowa Geological Survey, the Minnesota Geological Survey, the Minnesota Department of Natural Resources, the Minnesota Natural Resources Research Institute, the Nebraska Conservation and Survey Division and the South Dakota Geological Survey.

Covering more than 105,000 square miles, the new geophysical survey will use the latest technological developments that will allow scientists to develop high-resolution three-dimensional representations of geology to depths over 3200 feet (1 kilometer) below the surface.

The 3D models and maps produced from the survey will help understand the distribution of mineral and energy resources, as well as the potential for natural hazards. Data collected as part of this effort will be made public and used by the state agencies and the USGS to guide more detailed geologic mapping at local scales. 

Image shows a single-engine fixed-wing aircraft in flight
Photo of one the airplanes that will be used. The “boom” that extends behind the aircraft contains a magnetic sensor. Photo by Sander Geophysical Laboratories, used with permission.

The airplane will fly along pre-planned flight paths relatively low to the ground at more than 300 feet (100 meters) above the surface. The ground clearance will be increased to about 1,000 feet (300+ meters) over populated areas in order to comply with FAA regulations. Flight line separation will be more than 600 feet (200 meters) throughout the survey area.

Instruments on the airplane will measure variations in the Earth’s magnetic field and natural low-level radiation created by different rock types. This information will help researchers develop geologic maps in three dimensions.

The USGS is contracting with Sander Geophysics Ltd. and Dewberry to collect the geophysical data.

The scientific instruments on the airplane are completely passive with no emissions that pose a risk to humans, animals, or plant life. No photography or video data will be collected. The data collected will be made freely available to the public once complete. The aircraft will be flown by experienced pilots that are specially trained and approved for low-level flying. The companies work with the FAA to ensure flights are safe and in accordance with U.S. law. The surveys will be conducted during daylight hours only.

This survey fits into a broader effort by the USGS and many other state geological surveys, and other partners, including private companies, academics and State and Federal agencies to modernize our understanding of the Nation’s fundamental geologic framework and knowledge of mineral resources. This effort is known as the Earth Mapping Resources Initiative, and it includes airborne geophysical surveys like this one, geochemical reconnaissance surveys and geologic mapping projects.

For more information related to this survey see the project announcement.

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