Extreme fractionation of 234U238U and 230Th234U in spring waters,sediments, and fossils at the Pomme de Terre Valley,southwestern Missouri

Isotopic fractionation as great as 1600% exists between ²³⁴U and ²³⁸U in spring waters, sediments, and fossils in the Pomme de Terre Valley, southwestern Missouri. The activity ratios of ${}^{234}\text{U}{}^{238}\text{U}$ in five springs range from 7.2 to 16 in water which has been discharged for at least the past 30,000 years. The anomalies in ${}^{234}\text{U}{}^{238}\text{U}$ ratio in deep water have potential usefulness in hydrologic investigations in southern Missouri. Clayey units overlying the spring bog sediments of Trolinger Spring are enriched in ²³⁰Th relative to their parent ²³⁴U by as much as 720%. The results indicate that both preferential displacement via alpha recoil ejection and the preferential emplacement via recoiling and physical entrapment are significant processes that are occurring in the geologic environment.