Uranium in sediments

Abstract

An oceanographic approach is used to study the distribution of abnormal occurrences of uranium in sediments. The occurrences predominate in marine phosphorites, black marine shales, and deposits in terrestrial-fluvial sandstones and ancient conglomerites. In early Paleozoic times, marine shales accounted for the majority of uranium deposition. By the beginning of Tertiary time, the balance had shifted to predominant deposition in marine phosphorites which continued to the present. Much smaller total quantities of uranium are associated with terrestrial sandstones and ancient conglomerates, although its concentration is greater and its economic recovery is more feasible. All the abnormal occurrences fit into a unique niche in the hydrologic cycle, and emplacement was largely controlled by cycles of organic substances in water. Radiochemical analyses of Pa 231 , Th 230 , and Ra 226 were made on a few hundred samples from sandstone-type uranium deposits. These results, in comparison to the uranium content of samples, indicate that much of the uranium in terrestrial sediments is presently in a slow, continual state of migration toward the ocean.