Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired in late February to early March 2018 along 2,364 line-kilometers in the Shellmound, Mississippi study area. Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. RESOLVE frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at an average sensor flight height of 30 m above terrain to form block-style coverage with 250 to 1,000-meter spaced east-west flight lines. This data release includes the averaged and culled AEM data along all flight lines that were used to produce the final resistivity models (https://www.sciencebase.gov/catalog/item/5ca6a4e6e4b0c3b0064c2c2b). Digital data of the processed soundings are provided and fields are defined in the data dictionary (https://www.sciencebase.gov/catalog/item/5d0814b9e4b0e3d3115bdab6). An important driver for this survey is a managed aquifer recharge pilot project developed by the U.S. Department of Agriculture Agricultural Research Service investigating the use of bank filtration along the Tallahatchie River as a source for recharge in areas of significant groundwater decline by direct injection into the Mississippi River Valley Alluvial Aquifer (MRVA). Understanding the structure of the aquifer, including both shallow and deep confining units, is important for the success of this pilot engineering study and will be even more important for potential future large-scale engineering projects and groundwater model development efforts. REFERENCES U.S. Geological Survey, The National Map, 2017, 3DEP products and services: The National Map, 3D Elevation Program Web page, accessed October 2018 at https://nationalmap.gov/3DEP/3dep_prodserv.html.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired in late February to early March 2018 along 2,364 line-kilometers in the Shellmound, Mississippi study area. Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. RESOLVE frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain to form block-style coverage with 250 to 1,000-meter spaced east-west flight lines. This data release includes minimally processed (raw) AEM data, as well as unprocessed and processed (diurnally corrected and draped to terrain) magnetic data, and unprocessed and processed (following International Atomic Energy Agency Technical Report procedures) radiometric data, all as supplied by CGG Canada Services, Ltd. (https://www.sciencebase.gov/catalog/item/5ca6ce7ee4b0c3b0064c2ce5). Data acquisition and minimal processing was conducted by CGG Canada Services, Ltd. and described in detail in the contractor's report. Digital data from production flights are provided, and data fields are defined in the data dictionary. An important driver for this survey is a managed aquifer recharge pilot project developed by the U.S. Department of Agriculture Agricultural Research Service investigating the use of bank filtration along the Tallahatchie River as a source for recharge in areas of significant groundwater decline by direct injection into the Mississippi River Valley Alluvial Aquifer (MRVA). Understanding the structure of the aquifer, including both shallow and deep confining units, is important for the success of this pilot engineering study and will be even more important for potential future large-scale engineering projects and groundwater model development efforts. REFERENCES International Atomic Energy Agency, 1991, Airborne Gamma Ray Spectrometer Surveying, Technical Reports Series No. 323, IAEA, Vienna. U.S. Geological Survey, The National Map, 2017, 3DEP products and services: The National Map, 3D Elevation Program Web page, accessed October 2018 at https://nationalmap.gov/3DEP/3dep_prodserv.html.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired in late February to early March 2018 along 2,364 line-kilometers in the Shellmound, Mississippi study area. Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. RESOLVE frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil type. The survey was flown at an average sensor flight height of 30 m above terrain to form block-style coverage with 250 to 1,000-meter spaced east-west flight lines. A total field magnetic anomaly Grid eXchange File (.gxf) grid and a ternary radiometric geotiff image derived from the flight line data are provided (https://www.sciencebase.gov/catalog/item/5cd0ad9de4b09b8c0b79a53f). Additional details are provided in the processing steps. An important driver for this survey is a managed aquifer recharge pilot project developed by the U.S. Department of Agriculture Agricultural Research Service investigating the use of bank filtration along the Tallahatchie River as a source for recharge in areas of significant groundwater decline by direct injection into the Mississippi River Valley Alluvial Aquifer (MRVA). Understanding the structure of the aquifer, including both shallow and deep confining units, is important for the success of this pilot engineering study and will be even more important for potential future large-scale engineering projects and groundwater model development efforts.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired in late February to early March 2018 along 2,364 line-kilometers in the Shellmound, Mississippi study area. Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. RESOLVE frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain to form block-style coverage with 250 to 1,000-meter spaced east-west flight lines. This data release includes minimally processed (raw) AEM data as supplied by CGG Canada Services, Ltd. (https://www.sciencebase.gov/catalog/item/5ca6ce7ee4b0c3b0064c2ce5), the fully processed (averaged and culled) sounding data (https://www.sciencebase.gov/catalog/item/5d0814b9e4b0e3d3115bdab6), and laterally constrained inverted resistivity depth sections along all flight lines (https://www.sciencebase.gov/catalog/item/5ca6a4e6e4b0c3b0064c2c2b), as well as unprocessed and processed (diurnally corrected and draped to terrain) magnetic data (https://www.sciencebase.gov/catalog/item/5ca6ce7ee4b0c3b0064c2ce5), and unprocessed and processed (following International Atomic Energy Agency Technical Report procedures) radiometric data (https://www.sciencebase.gov/catalog/item/5ca6ce7ee4b0c3b0064c2ce5). Data acquisition and minimal processing were conducted by CGG Canada Services, Ltd. and described in detail in the contractor's report. Digital data from production flights are provided, and data fields are defined in the data dictionary. A total field magnetic anomaly grid and a ternary radiometric image are provided as well (https://www.sciencebase.gov/catalog/item/5cd0ad9de4b09b8c0b79a53f). An important driver for this survey is a managed aquifer recharge pilot project developed by the U.S. Department of Agriculture Agricultural Research Service investigating the use of bank filtration along the Tallahatchie River as a source for recharge in areas of significant groundwater decline by direct injection into the Mississippi River Valley Alluvial Aquifer (MRVA). Understanding the structure of the aquifer, including both shallow and deep confining units, is important for the success of this pilot engineering study and will be even more important for potential future large-scale engineering projects and groundwater model development efforts. REFERENCES International Atomic Energy Agency, 1991, Airborne Gamma Ray Spectrometer Surveying, Technical Reports Series No. 323, IAEA, Vienna. U.S. Geological Survey, The National Map, 2017, 3DEP products and services: The National Map, 3D Elevation Program Web page, accessed October 2018 at https://nationalmap.gov/3DEP/3dep_prodserv.html.

Shallow soil characteristics were mapped near Shellmound, Mississippi, using the DualEM 421 electromagnetic sensor in October 2018. Data were acquired by towing the DualEM sensor on a wheeled cart behind an all-terrain vehicle (ATV), with the sensor at a height of 0.432 meters (m) above the ground surface. Approximately 175 line-kilometers of data were acquired over an area of nearly four square-kilometers, with 25 m separation between survey lines. Data were manually edited for noise sources such as powerlines or other buried structures and averaged to regular output soundings every 5 m along survey lines. The processed data were inverted to recover models of electrical resistivity structure as a function of depth at each sounding location using a spatially constrained inversion. This data release contains the raw and processed data, as well as inverted resistivity models. Model results show typical depth of investigation from about 4 – 6 m, with spatial variability in mapped electrical resistivity characteristic of fluvial deposition of sediments in channels and scroll bar features adjacent to the Tallahatchie River and nearby abandoned meander channels.

Shallow soil characteristics were mapped near Shellmound, Mississippi, using the DualEM 421 electromagnetic sensor in October 2018. Data were acquired by towing the DualEM sensor on a wheeled cart behind an ATV, with the sensor at a height of 0.432 meters (m) above the ground surface. Approximately 175 line-kilometers of data were acquired over an area of nearly four square kilometers, with 25 m separation between survey lines. Data were manually edited for noise sources such as powerlines or other buried structures, and averaged to regular output soundings every 5 m along survey lines. This data release contains the processed data that have been averaged and culled to produce final resistivity models. Digital data of the processed soundings are provided and fields are defined in the data dictionary.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired in late February to early March 2018 along 2,364 line-kilometers in the Shellmound, Mississippi study area. Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. RESOLVE frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at an average sensor flight height of 30 m above terrain to form block-style coverage with 250 to 1,000-meter spaced east-west flight lines. This data release includes laterally-constrained inverted depth sections along all flight lines from the AEM data. Digital data of the laterally constrained inversions are provided and fields are defined in the data dictionary (https://www.sciencebase.gov/catalog/item/5ca6a4e6e4b0c3b0064c2c2b). An important driver for this survey is a managed aquifer recharge pilot project developed by the U.S. Department of Agriculture Agricultural Research Service investigating the use of bank filtration along the Tallahatchie River as a source for recharge in areas of significant groundwater decline by direct injection into the Mississippi River Valley Alluvial Aquifer (MRVA). Understanding the structure of the aquifer, including both shallow and deep confining units, is important for the success of this pilot engineering study and will be even more important for potential future large-scale engineering projects and groundwater model development efforts. REFERENCES U.S. Geological Survey, The National Map, 2017, 3DEP products and services: The National Map, 3D Elevation Program Web page, accessed October 2018 at https://nationalmap.gov/3DEP/3dep_prodserv.html.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired November 2018 to February 2019 along 16,816 line-kilometers (line-km) over the Mississippi Alluvial Plain (MAP). Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. Resolve frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain with 6- to 12-kilometer spaced east-west flight lines. The main survey block covers 13,641 line-km, including two north-south tie lines extending the length of the survey. Several rivers were surveyed along their center axes, covering 2,640 line-km (flight line numbers 8010000-8100001 nonsuccessive), and two separate inset grids were flown: (1) Crowley's Ridge in Arkansas with 1.5-km spaced east-west flights for a total of 406 line-km (flight line numbers 24025-24477 nonsuccessive) and (2) University of Memphis focus area in Tennessee with variable line spacing for a total of 129 line-km (flight line numbers 30010-30060 and 39010-39050 nonsuccessive). This data release includes the averaged and culled AEM data along all flight lines that were used to produce the final resistivity models (https://www.sciencebase.gov/catalog/item/5d76ba5ce4b0c4f70d01ff94). Digital data of the processed soundings are provided and fields are defined in the data dictionary (https://www.sciencebase.gov/catalog/item/5d76bac9e4b0c4f70d01ff9d).

Airborne electromagnetic (AEM) and magnetic survey data were collected during April and May 2019 along 1,467 line-kilometers in the San Juan-Silverton Caldera complex, Colorado, in the Southern Rocky Mountain Volcanic Field. Data were acquired by Geotech, Ltd. with the versatile time-domain electromagnetic (VTEM-ET) system together with a Geometrics optically pumped cesium vapor magnetometer. The survey was flown at a mean flight height of 140 meters (m) above terrain in various line directions and line spacings ranging from 150 m to 600 m. Multiple variable-spaced lines were flown along rivers and streams in the survey area. USGS provided the contractor with the San Juan National Forest Lidar Point Cloud elevation dataset imported from the USGS National MAP 3D Elevation Program (U.S. Geological Survey, 2019). AEM data were inverted to produce models of electrical resistivity along flight paths. References: U.S. Geological Survey, The National Map, 2019, 3DEP products and services: The National Map, 3D Elevation Program Web page, accessed April 2019 at https://nationalmap.gov/3DEP/3dep_prodserv.html First posted September 16, 2020 Revised August 19, 2022, ver.2.0 Changes in version 2.0: 1. Updated contractor package and raw data to remediate an erroneous calculation of transmitter/receiver altitude. 2. Converted dataset to netCDF format. 3. Added inverted resistivity models for the entire dataset.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired November 2018 to February 2019 along 16,816 line-kilometers (line-km) over the Mississippi Alluvial Plain (MAP). Data were acquired by CGG Canada Services, Ltd. with three different helicopter-borne sensors: the CGG Canada Services, Ltd. Resolve frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain with 6- to 12-kilometer spaced east-west flight lines. The main survey block covers 13,641 line-km, including two north-south tie lines extending the length of the survey. Several rivers were surveyed along their center axes, covering 2,640 line-km (flight line numbers 8010000-8100001 nonsuccessive), and two separate inset grids were flown: (1) Crowley's Ridge in Arkansas with 1.5-km spaced east-west flights for a total of 406 line-km (flight line numbers 24025-24477 nonsuccessive) and (2) University of Memphis focus area in Tennessee with variable line spacing for a total of 129 line-km (flight line numbers 30010-30060 and 39010-39050 nonsuccessive). A total field magnetic anomaly Grid eXchange File (.gxf) grid and a ternary radiometric geotiff image derived from the flight line data are provided (https://www.sciencebase.gov/catalog/item/5d76baaae4b0c4f70d01ff9a). Additional details are provided in the processing steps.