Abstract: Uranium occurrences in the Yeşilyurt area of Western Turkey occur in fluviatile sedimentary rocks which are underlain by low-to medium-grade metamorphic rocks of the Menderes massif.These occurrences are found in Neogene conglomerate and sandstone beds that contain a matrix ofabundant clay and silt. Uranium is present as a matrix impregnation in tabular lenses within the sandstone and conglomerate beds. Both oxidized and unoxidized occurrences occur. Both types are disseminated uniformly throughout the fine grained clay and silt matrix rich in carbonaceous matter. Unoxidizeduranium occurrences show no direct correlation with pyrite and siderite abundance.Ore grade uranium (0.05 % U3O8) concentrations in the oxidized occurrences are confined to sandstoneand conglomerate beds with clay and hematite matrix containing little or no calcite whereas very lowgrade (< 0.01 % U3O8) uranium concentrations occur in calcite-rich matrix of sandstone and conglomeratebeds. Authigenic pyrite and siderite formed during diagenesis. Uranium in solution was first adsorbedby clays and carbonaceous matrix and further reduced by mobile H2S.A large amount of uranium, concentrated to ore grades in the reduced sandstones and conglomerates, was dissolved by carbonate-rich solutions ascending along the graben margin growth fault and redistributed throughout the fluviatile sediments. A few occurrences of uranium survived the severealteration represented mainly by calcite and hematite. All the occurrences are epigenetic in originformed by groundwater solution that moved through the host rock. The massive gneisses are believed tohave been the only source of uranium.