Media Alert: Low-level helicopter flights to image geology over parts of Iowa, Illinois, and Wisconsin

Media Advisory: Members of the news media are invited to attend a media day at the Dubuque Regional Airport to see first-hand the aircraft and equipment that will be used to image geology during a U.S. Geological Survey Earth Mapping Resources Initiative (Earth MRI) low-level airborne survey of the tristate region later this month. View the full advisoryhere.

RESTON, Va. - Low-level helicopter flights are planned over areas of Iowa, Illinois, and Wisconsin to image geology using airborne geophysical technology.

The survey will be conducted from October 2024 for approximately one to two months, weather and flight restriction permitting. Surveying is expected to be completed by December of 2024.

Flights will cover areas within the Iowa counties of Clayton, Dubuque, and Jackson; Wisconsin counties of Grant and Lafayette; and Jo Daviess County in Illinois.

The flights will be based out of the Dubuque, Iowa area. Flights could shift with little warning to other parts of the survey area as necessary to minimize ferrying distances and avoid adverse flying conditions.

The purpose of the airborne electromagnetic (AEM) survey is to provide images of subsurface electrical resistivity that expand the fundamental knowledge of geology underpinning an area near Dubuque, Iowa and spanning portions of Illinois, Iowa and Wisconsin.

The helicopter will fly along pre-planned flight paths relatively low to the ground at about 100-200 feet (30-60 meters) above the land surface. The ground clearance will be increased as needed and will comply with Federal Aviation Administration (FAA) regulations. Flight lines will be flown along lines of variable orientation with an approximate spacing of 1,300 ft (400 m).

The survey will use a helicopter equipped with an elongated tube-like "bird" slung below the aircraft. Sensors in the bird will measure small electromagnetic signals and variations in the Earth's magnetic field that can be used to map geologic features.

None of the instruments carried beneath or on the aircraft pose a health risk to people, animals, or plant life. No photography or video data will be collected. The data collected will be made freely available to the public on ScienceBase, typically within one year of flight completion. The aircraft will be flown by experienced pilots who are specially trained and approved for low-level flying. The survey company works with the FAA to ensure flights are safe and in accordance with U.S. law.

The surveys will be conducted during daylight hours only. Surveys do not occur over densely populated areas and the helicopter will not directly overfly buildings at low altitude.

The survey is funded by the USGS Earth Mapping Resources Initiative and is designed to meet needs related to mineral resource assessments, regional geologic framework and mapping studies, as well as water resource investigations and surficial mapping studies. The AEM survey is focused on a phosphate horizon at the base of a regional shale unit that shows local enrichment in Rare-Earth Element concentrations. The primary goals of the survey are to map the thickness of unconsolidated sediments, the spatial extent and thickness of the regional shale unit, and the depth to the top of an underlying limestone unit.

The new geophysical data will be processed to develop high-resolution three-dimensional representations of near-surface geology at depths up to 300 ft (roughly 100 meters) below the surface. The 3D models and maps derived from this project are important for improving our understanding of critical mineral resource potential, water resources, groundwater pathways near legacy mining areas, parameters for infrastructure and land use planning.

The survey fits into a broader effort by the USGS, Iowa Geological Survey, Illinois State Geological Survey, Wisconsin Geological and Natural History Survey, 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, topographic mapping using LiDAR technology, hyperspectral surveys, and geologic mapping projects.

The USGS has contracted Fugro and Xcalibur Smart Mapping to collect data.