[en] The problem to be resolved was the age of the mound spring sediments on the margin of the Great Artesian Basin to the south and southwest of Lake Eyre. Nine samples from six springs and two from neighbouring dune fields were collected. The parent and daughter nuclides for the uranium and thorium decay chains have been comprehensively measured by a variety of techniques: DNA, thick-source alpha particle counting, field scintillometry, high resolution gamma spectrometry and high resolution alpha spectrometry. Gross radioactive disequilibrium in the uranium chain is found for the spring samples. The activity, in Bq kg^-1, for the uranium chain at and below radium, compared with the parent uranium and its immediate daughters, ranges from an excess factor of two to a factor of six, depending on the age of the spring mound deposit. This is interpreted as evidence that radium is being carried up into the springs with artesian groundwater and deposited in the spring mound sediments. There is also evidence for a small excess of thorium. The ages of the spring mound deposits have been successfully found by thermoluminescence. They range from about 20 ka to 500 ka. The disequilibrium suggests why attempts to use uranium series dating have not been successful