Robert P. Kucks 2005 Duval, Joseph S. Carson, John M. Holman, Peter B. Darnley, Arthur G. 2005 U.S. Geological Survey Open-File Report 2005-1413 http://pubs.usgs.gov/of/2005/1413/ Aerial gamma-ray surveys measure the gamma-ray flux produced by the radioactive decay of the naturally occurring elements K-40, U-238, and Th-232 in the top few centimeters of rock or soil. If the gamma-ray system is properly calibrated the data can be expressed in terms of the estimated concentrations of the radioactive elements. A ternary color-composite image was generated by commercial software Geosoft Oasismontaj to map the combination of all three elements. During the period 1975-83, the U.S. Department of Energy carried out the National Uranium Resource Evaluation (NURE) Program, which included aerial gamma-ray surveys of most of the United States. These data were reprocessed to generate this product. Digital Data Series DDS-9 (CD-ROM) contains gridded radiometric geophysical data images that were created for the Decade of North American Geology (DNAG) but only available for the U.S. Because uranium, thorium, and potassium concentration data are useful in geologic studies and because the NURE data are the only nationwide database on the natural radiation environment, the U.S. Geological Survey reprocessed the aerial gamma-ray data to produce maps showing surface concentrations of potassium, uranium, and thorium for the conterminous United States. 1999 2005 all available NURE data for the U.S. has been processed Complete None planned -168.0 -53.0 71.33 25.0 None None Robert P. Kucks U.S. Geological Survey mailing address

Box 25046, MS 964 Denver Federal Center

Denver CO 80225-0046 USA (303) 236-1405 rkucks@usgs.gov The U.S Geological Survey reprocessed the aerial gamma-ray (NURE) data to produce maps showing surface concentrations of potassium, uranium, and thorium for the conterminous United States. These maps have been released as USGS Open-File Reports. Some of the reprocessed data have also been released in profile form. The Canadian Geological Survey data were processed by the Radiation Geophysics Section of the CGS. See Open-File Report 2005-1413 for further references. USGS employees: Duval, Riggle, and Snyder Canadian GS employees: Carson, Holman, and Darnley The NURE data were originaly stored in ASCII format on 9-track magnetic tapes. They are currently available on the report DVD as Geosoft Oasismontaj databases (.gdb) but can be converted to ASCII form. none ternary, gamma-ray, radiometric none United States, Canada make these surveys were calibrated, many of the earlier surveys were done without calibration and conversion to the concentrations of the radioactive elements. Detailed examinations of the digital data available on magnetic tape also showed that many of the "calibrated" surveys do not match the data from other "calibrated" surveys of adjacent areas. For these reasons, the data must be corrected to obtain a consistent data base for the conterminous United States. If the gamma-ray system is properly calibrated the data can be expressed in terms of the estimated concentrations of the radioactive elements. 0.1 percent potassium; 0.1 ppm uranium and thorium The potassium concentration data are usually expressed in units of percent potassium (percent K). The uranium and thorium concentration data are usually expressed in units of parts per million equivalent (ppm). Although many of the airborne gamma-ray systems used to make these surveys were calibrated, many of the earlier surveys were done without calibration and conversion to the concentrations of the radioactive elements. Detailed examinations of the digital data available on magnetic tape also showed that many of the "calibrated" surveys do not match the data from other "calibrated" surveys of adjacent areas. For these reasons, the data must be corrected to obtain a consistent data base for the conterminous United States. Data coverage extends thoroughly across the conterminous US. Significant gaps exist in the coverage of Alaska, especially the area south of the North Slope but north of the Brooks Range, and the Aleutian islands. Central Canada is covered as are most of the Atlantic provinces and eastern Ontario. Large gaps exist in Quebec, the western provinces, and both northern and southwestern Ontario. The accuracy was dependent on the flight specifications and tolerances of the Department of Energy during their surveying. 100 Dependent on flight positioning recovery used by NURE project The accuracy was dependent on the flight specifications and tolerances of the Department of Energy during their surveying. 100 Dependent on flight positioning recovery used by NURE project Duval, Joseph S. Darnley, Arthur G. (editor) Garrett, Robert G. (editor) 1990 Journal of Geochemical Exploration 1975 1983 original data collection period for the NURE program Duval, Darnley, and Garrett 1990 Material re-processed to obtain the present grids Duval, Joseph S. Jones, William J. Riggle, Frederick R. Pitkin, James A. 1990 map U.S. Geological Survey Open-File Report 90-338 CD-ROM 1975 1983 original data collection period for the NURE program OFR 90-338 Material re-processed to obtain the present grids Phillips, Jeffrey D. Duval, Joseph S. Ambroziak, Russell A. 1993 U.S. Geological Survey Digital Data Series DDS-9 CD-ROM 1975 1983 original data collection period for the NURE program DDS-9 Material re-processed to obtain the present grids Duval, Joseph S. 1995 1 U.S. Geological Survey Digital Data Series DDS-31 CD-ROM 1975 1983 original data collection period for the NURE program DDS-31 Release 1 Material re-processed to obtain the present grids Duval, Joseph S. Riggle, Frederic E. 1999 2 U.S. Geological Survey Digital Data Series DDS-31 CD-ROM 1975 1983 original data collection period for the NURE program DDS-31 Release 2 Material re-processed to obtain the present grids The gamma-ray data were extracted from the NURE files and Canadian data sets; then projected, gridded, and displayed in a ternary form using the commercial software package Geosoft Oasis Montaj. Three elemental grids were calculated, one each for K, U, and Th, and a fourth that is the composite of each of these, referred to here as CCM. 2005 Robert P. Kucks U.S. Geological Survey

Box 25046, MS 964 Denver Federal Center

Denver CO 80225-0046 USA mailing address rkucks@usgs.gov (303)236-1405 The gamma-ray absorbed dose was calculated using the equation D = 13.2 K + 5.48 eU + 2.72 eTh where K is the concentration of potassium in units of percent K, eU is the concentration of uranium in ppm, eTh is the concentration of thorium in ppm, and D is the absorbed dose in nanoGrays per hour (nGy/hr). This equation is based upon the equation published by Grasty (see OF Report). The grid of the gamma-ray absorbed dose was calculated using the grids of potassium, uranium, and thorium concentrations. That grid was then displayed in image form using the commercial software package Geosoft Oasismontaj. 2005 Robert P. Kucks U.S. Geological Survey

Box 25046, MS 964 Denver Federal Center

Denver CO 80225-0046 USA mailing address rkucks@usgs.gov (303)236-1405 Raster pixel 2371 5823 0.02 0.02 Decimal degrees North American Datum of 1983 Geodetic Reference System 80 6378137.0 298.257222101 CCM grid cell Gamma-ray flux produced by the radioactive decay of naturally occuring elements expressed in concentrations of radioactive elements potassium percentage, uranium and thorium ppm expressed in units of percent potassium (percent K) and equivalent concentration of uranium and thorium in ppm (ppm eU & ppm eTh) Duval, Darnley, and Garrett 1990 0.0 100.0 percent of element 0.1 (no value) Cells lacking color (white) represent areas of no data in image. K grid cell Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements potassium percentage expressed in units of percent potassium (percent K) 0.0 4.0 percent K 0.1 (no value) Cells lacking color (white) represent areas of no data in image. Th grid cell Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements thorium concentration expressed in units of parts per million equivalent thorium (ppm eTh) 0.0 24.0 ppm eTh 0.1 (no value) Cells lacking color (white) represent areas of no data in image. U grid cell Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations of radioactive elements uranium concentration expressed in units of parts per million equivalent uranium (ppm eU) 0.0 6.0 ppm eU 0.1 (no value) Cells lacking color (white) represent areas of no data in image. exp grid cell Gamma-ray flux produced by the radioactive decay of naturally occuring elements, expressed in concentrations absorbed doses nanoGrays per hour gamma-ray absorbed dose rate 0.0 125.0 nanoGrays per hour 1 (no value) Cells lacking color (white) represent areas of no data in image. USGS Map Distribution mailing address

Box 25286, Building 810 Denver Federal Center

Denver CO 80225 USA (888)ASK-USGS U.S. Geological Survey Open-File Report 2005-1413 The USGS has made every effort to verify the veracity of this information, but is not liable for any inaccuracies. Geotiff Arc-Info image format pixel none 40.5 2005 20060222 Robert P. Kucks U.S. Geological Survey rkucks@usgs.gov mailing address

Box 25046, MS 964 Denver Federal Center

Denver CO 80225 USA (303)236-1405 Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998