Unconformity-type uranium deposits host high grades relative to other uranium deposits and include some of the largest and richest deposits known. They occur in close proximity to major unconformities between relatively quartz- rich sandstones comprising the basal
relatively undeformed basins and deformed metamorphic basement rocks. These sedimentary basins are typically of Proterozoic age, however some
Phanerozoic examples exist. portion of sedimentary