Projections of future demand for nuclear-powered electrical generating capacity indicate that a large amount of uranium will be needed by the year 2000. Uranium deposits of the type found in the Colorado Plateau region and in Tertiary basins in Wyoming have been the principal source of uranium in the United States, and potential resources in such deposits are large. Even so, they may not be fully adequate to supply all the uranium needed. For this reason, attention is focused here on a variant type of deposit that so far has not yielded much uranium, but that may have a significant potential because the deposits are widely distributed in a geologic setting that is extensive in western United States.

The deposits, like the better known Colorado Plateau and Wyoming deposits, consist of uranium minerals interstitial in continental sandstone and conglomerate that also contain carbonized plant remains. The deposits are in lenticular beds within sequences of Tertiary volcanic rocks, mostly at or near the base of a sequence. The sedimentary lenses containing mineralized rock are irregular, probably because their form and distribution were controlled in part by underlying pre-volcanic topography and in part by drainage changes on an unstable volcanic terrane.

If geologic ingenuity can discern the irregular pattern of the host lenses under a cover of volcanic rocks and establish the relation of deposits to the pattern, new uranium resources might be the reward.

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