The U.S. Geological Survey, in cooperation with the U.S. Air Force Civil Engineering Center, collected borehole geophysical data and performed simple aquifer tests to estimate the thickness and hydraulic properties of surficial deposits. The purpose of data collection was to create generalized contour maps of Pierre Shale elevation and surficial deposit thickness within and near Ellsworth Air Force Base. Natural gamma and electromagnetic induction (EMI) data were collected to refine or determine surficial deposit thickness at selected wells. Additionally, data from previous geophysical studies and drillers logs were compiled and combined with results from natural gamma and electromagnetic induction data to provide a more spatially complete image of the subsurface. Borehole nuclear magnetic (bNMR) resonance data were collected to estimate hydraulic conductivity and water content of surficial deposits overlying Pierre Shale. Simple aquifer tests using water slugs (slug tests) were performed to estimate hydraulic conductivity of surficial deposits and results were compared to hydraulic conductivity estimates from borehole nuclear magnetic resonance data. The U.S. Geological Survey also tested the usefulness of colloidal borescope flowmeter (CBFM) logging for determining the horizontal flow direction and velocity of groundwater in the study area.

In 2022, the USGS, in cooperation with the U.S. Air Force Civil Engineer Center (USAF/CEC), performed geophysical surveys at two areas of interest within and near Ellsworth Air Force Base (EAFB) to delineate the Cretaceous Pierre Shale bedrock. Electrical resistivity tomography (ERT) data were collected in two grid patterns using the dipole-dipole array within and near EAFB and site information—including latitude, longitude, and elevation—were surveyed along geophysical transects comprising the grids using real-time kinematic (RTK) techniques. The purpose of collecting ERT data in grids rather than along individual transects was to create three-dimensional (3D) surfaces of the bedrock, which improve site characterization by providing higher resolution images of the bedrock compared to transects that provide only two-dimensional (2D) information. ERT data were processed using EarthImager2D software from Advanced Geosciences, Inc. (https://www.agiusa.com/agi-earthimager-2d) to remove noisy measurements and produce subsurface electrical resistivity profiles. Monitoring wells and soil borings with depth to bedrock information from the South Dakota Department of Agriculture and Natural Resources and Ellsworth Air Force Base were combined with subsurface electrical resistivity profiles to delineate the bedrock surface elevation along each transect in the grids. After bedrock delineation was completed, interpolation techniques were used to construct three-dimensional bedrock elevation surfaces for each grid. Unprocessed and processed geophysical are provided in zipped folders (.zip) as machine- and user-readable files with accompanying text files that explains the content of each file. Site information from RTK surveys, bedrock delineation results along each transect in the two grids, and monitoring wells or soil borings used to aid delineation are included as comma-separated values (.csv) files.

Geospatial datasets were developed to estimate the depth to the top of the Dakota Sandstone in feet below land surface datum within the Ute Mountain Ute Reservation in Colorado. This study was completed by the U.S. Geological Survey (USGS) in cooperation with the Ute Mountain Ute Tribe. One dataset was created for the contours showing the altitude (in feet) of the top of the Dakota Sandstone (shapefile Kd_talt_hand), and a second dataset was created for polygons representing the outcrops of the Dakota Sandstone (shapefile Dakota_outcrop_poly). These two datasets were used in combination with USGS digital elevation models (DEM) to create a dataset for the depth of the top of the Dakota Sandstone below the land surface contoured at a 100-foot interval (shapefile kd_depth_ci100). The kd_depth_ci100 dataset was used to generate a figure showing the generalized depth to the top of the Dakota Sandstone in feet below land surface in Bauch and Arnold (2019).

Geospatial datasets were developed to estimate the depth to the top of the Dakota Sandstone in feet below land surface datum within the Ute Mountain Ute Reservation in Colorado. This study was completed by the U.S. Geological Survey (USGS) in cooperation with the Ute Mountain Ute Tribe. One dataset was created for the contours showing the altitude (in feet) of the top of the Dakota Sandstone (shapefile Kd_talt_hand), and a second dataset was created for polygons representing the outcrops of the Dakota Sandstone (shapefile Dakota_outcrop_poly). These two datasets were used in combination with USGS digital elevation models (DEM) to create a dataset for the depth of the top of the Dakota Sandstone below the land surface contoured at a 100-foot interval (shapefile kd_depth_ci100). The kd_depth_ci100 dataset was used to generate a figure showing the generalized depth to the top of the Dakota Sandstone in feet below land surface in Bauch and Arnold (2019).

Airborne electromagnetic (AEM) and magnetic survey data were collected during November and December 2016 along 4,212 line-kilometers over Yellowstone National Park, Wyoming. The survey was conducted as part of a study of the subsurface geologic structure and geothermal and groundwater resources of Yellowstone National Park. The survey was designed to image the subsurface plumbing of Yellowstone's myriad thermal features by constraining the geometry of the major hydrostratigraphic contacts and mapping regional-scale geologic structures. Data were acquired by SkyTEM ApS with the SkyTEM 312M time-domain helicopter-borne electromagnetic system together with a Geometrics G822A cesium vapor magnetometer. The survey was flown along six block-style line groups with a nominal line spacing of 450 meters (m), one block-style line group with a nominal line spacing of 250 m, two block-style line groups with a nominal line spacing of 150 m, and a series of regional reconnaissance lines with 5 kilometer (km) nominal line spacing. Due to terrain complexity, the mean flight height was about 48 m. The AEM depth of investigation varies considerably with subsurface resistivity; however, the maximum depth of investigation is about 700 m. This data release includes manually processed AEM data from production flights and inverted models. A shapefile of the AEM flightlines and minimally processed (raw) AEM data supplied by SkyTem Aps are available at https://doi.org/10.5066/P9MCJ9B6.

Airborne electromagnetic (AEM) and magnetic survey data were collected during November and December 2016 along 4,212 line-kilometers over Yellowstone National Park, Wyoming. The survey was conducted as part of a study of the subsurface geologic structure and geothermal and groundwater resources of Yellowstone National Park. The survey was designed to image the subsurface plumbing of Yellowstone's myriad thermal features by constraining the geometry of the major hydrostratigraphic contacts and mapping regional-scale geologic structures. Data were acquired by SkyTEM ApS with the SkyTEM 312M time-domain helicopter-borne electromagnetic system together with a Geometrics G822A cesium vapor magnetometer. The survey was flown along six block-style line groups with a nominal line spacing of 450 meters (m), one block-style line group with a nominal line spacing of 250 m, two block-style line groups with a nominal line spacing of 150 m, and a series of regional reconnaissance lines with 5 kilometer (km) nominal line spacing. Due to terrain complexity, the mean flight height was about 48 m. The AEM depth of investigation varies considerably with subsurface resistivity; however, the maximum depth of investigation is about 700 m. This data release includes manually processed AEM data from production flights and inverted models. A shapefile of the AEM flightlines and minimally processed (raw) AEM data supplied by SkyTem Aps are available at https://doi.org/10.5066/P9MCJ9B6.

The Air Force Research Laboratory (AFRL) is about 7 kilometers southwest of Boron, California, and covers 320 square kilometers of Edwards Air Force Base. The AFRL consists of 12 facilities for testing full-size rocket engines, engine components, and liquid and solid propellants. The historical release of contaminants from rocket test stands, evaporation ponds, burn pits, catch basins, and leaking waste-collection tanks has contaminated groundwater in the AFRL. Groundwater aquifers near the AFRL are mostly restricted to fractured granitic bedrock, but previous studies indicate that groundwater and associated contaminants have moved into alluvium to the north and northwest. The U.S. Geological Survey (USGS) and the U.S. Air Force entered into a cooperative agreement to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. As part of that effort, surface geophysical data were collected to: (1) assess changes in the depth to bedrock with increasing distance from the AFRL; (2) to provide information on shallow geologic structures near the AFRL; and (3) to assess the presence of any faults that could present partial barriers to groundwater flow. The surface geophysical methods collected northwest of the AFRL in 2018 were electrical resistivity tomography (ERT), horizontal-to-vertical spectral ratio (HVSR) passive seismic, and time-domain electromagnetic (TEM).

The Air Force Research Laboratory (AFRL) is about 7 kilometers southwest of Boron, California, and covers 320 square kilometers of Edwards Air Force Base. The AFRL consists of 12 facilities for testing full-size rocket engines, engine components, and liquid and solid propellants. The historical release of contaminants from rocket test stands, evaporation ponds, burn pits, catch basins, and leaking waste-collection tanks has contaminated groundwater in the AFRL. Groundwater aquifers near the AFRL are mostly restricted to fractured granitic bedrock, but previous studies indicate that groundwater and associated contaminants have moved into alluvium to the north and northwest. The U.S. Geological Survey (USGS) and the U.S. Air Force entered into a cooperative agreement to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. As part of that effort, surface geophysical data were collected to: (1) assess changes in the depth to bedrock with increasing distance from the AFRL; (2) to provide information on shallow geologic structures near the AFRL; and (3) to assess the presence of any faults that could present partial barriers to groundwater flow. The surface geophysical methods collected northwest of the AFRL in 2018 were electrical resistivity tomography (ERT), horizontal-to-vertical spectral ratio (HVSR) passive seismic, and time-domain electromagnetic (TEM).

Radiometric data collected as part of a high-resolution airborne magnetic and radiometric survey over the southwest portion of the Colorado Mineral Belt in southwestern Colorado are provided as digital flight-line and grid files. Radiometric (or gamma-ray) surveys measure naturally occurring low-level radiation and are sensitive to the presence of rocks within 30 cm of the surface that are enriched in uranium, thorium, or potassium. Data for this survey were acquired by NV5 Geospatial, Inc. and its sub-contractors Precision GeoSurveys, Inc. and EDCON-PRJ, Inc under contract with the USGS. The survey was flown in September and October of 2023 using a helicopter equipped with a gamma-ray spectrometer stowed onboard. The helicopter pilots followed pre-planned flight paths in a grid-like pattern, with north-south lines spaced 200 meters apart and east-west lines spaced 1,000 meters apart. Lines were flown 100 meters above ground as much as possible to maximize the detection of gamma rays. This clearance could be realized in areas of low relief but higher clearances, as much as 200-500 meters, were required over rugged terrain and populated areas for safety reasons. Areas with restricted airspace, such as Wilderness Areas, were avoided. A total of 28,472 linear kilometers of data were collected along the lines, covering a 4,719 square-kilometer irregular area. EDCON-PRJ performed extensive data processing after completion of flying and delivered the final data and report in April 2024.

Radiometric data collected as part of a high-resolution airborne magnetic and radiometric survey over the southwest portion of the Colorado Mineral Belt in southwestern Colorado are provided as digital flight-line and grid files. Radiometric (or gamma-ray) surveys measure naturally occurring low-level radiation and are sensitive to the presence of rocks within 30 cm of the surface that are enriched in uranium, thorium, or potassium. Data for this survey were acquired by NV5 Geospatial, Inc. and its sub-contractors Precision GeoSurveys, Inc. and EDCON-PRJ, Inc under contract with the USGS. The survey was flown in September and October of 2023 using a helicopter equipped with a gamma-ray spectrometer stowed onboard. The helicopter pilots followed pre-planned flight paths in a grid-like pattern, with north-south lines spaced 200 meters apart and east-west lines spaced 1,000 meters apart. Lines were flown 100 meters above ground as much as possible to maximize the detection of gamma rays. This clearance could be realized in areas of low relief but higher clearances, as much as 200-500 meters, were required over rugged terrain and populated areas for safety reasons. Areas with restricted airspace, such as Wilderness Areas, were avoided. A total of 28,472 linear kilometers of data were collected along the lines, covering a 4,719 square-kilometer irregular area. EDCON-PRJ performed extensive data processing after completion of flying and delivered the final data and report in April 2024.