[en] The concentrations of natural radionuclides of the ²³⁸U and /232/Th series are reported in several cores and in ten deep and five shallow briny groundwaters from various formations in the Palo Duro Basin. The formations include Granite Wash, Pennsylvanian Granite Wash, Wolfcamp Carbonate, Pennsylvanian Carbonate, Seven River, Queen Grayburg, San Andres, Yates and Salado. The natural radionuclide data in cores suggest that the radionuclides have not migrated or been leached for at least a period of about 1 million years. Relative to the U and Th concentrations in cores, the brines are depleted by a factor of 10⁴ to 10⁵, indicating extremely low solubility of U and Th in brines. The natural radionuclide data in brines suggest that radium is not sorbed significantly and thus not retarded in nine deep brines. Radium is somewhat sorbed in one deep brine of Wolfcamp Carbonate and significantly sorbed in shallow brines. Relative to radium, the U, Th, Pb, Bi, and Po radionuclides are highly retarded by sorption. The retardation factors for ²²⁸Th range from 10² to 10³, whereas those for ²³⁰Th and ²³⁴U range from 10³ to 10⁵, depending on the formation. The ²³⁴U/²³⁸U ratios in these brines are constant at about 1.5. The magnitude of the ²³⁴U/²³⁰Th ratio appears to reflect the degree of redox state of the aquifer's environment. The ²³⁴U/²³⁰Th ratio in nine deep brines is about unity, suggesting that U, like Th⁺⁴, is in the +4 state, which in turn suggests a reduced environment. 49 refs., 23 figs., 18 tabs