DETAILED AERIAL GAMMA-RAY SURVEYS OF PARTS OF THE ALBUQUERQUE BASIN, NEW MEXICO

The U.S. Geological Survey acquired two detailed aerial gamma-ray and magnetic surveys over parts of the Albuquerque Basin in New Mexico as part of a larger study of the hydrology of the basin. These surveys were flown with a line spacing of 150 m and a nominal altitude of 150 m above the ground. Both surveys were flown over areas of sedimentary basin fill deposits and the lines were flown in an east-west direction. The data were gridded and grids of potassium, uranium, and thorium were analyzed using a maximum-likelihood classification technique to define areas with statistically similar data. The results of the classification analysis were further analyzed and interpreted to produce radiometric map units for comparison with mapped geologic units. The radiometric map units generally correlate with the mapped geology but some significant differences are apparent. Some of these differences may reflect the fact that available geologic maps are relatively small scale but some of the differences suggest a need to reexamine the mapped geology. Also of interest is the fact that some of the curvilinear features observed in the magnetic data coincide with changes in the radiometric data. This result indicates that some of the curvilinear features correspond to geologic contacts between units that have different magnetic properties.