ABSTRACT

To define favorable areas for uranium mineralization in the Upper Tertiary of the east Texas and west Louisiana Gulf Coast, sand trends were mapped in four intervals above the Catahoula Formation. Because the difficulty of correlating fluvial deposits is compounded in shallow strata by fresh and brackish ground water distorting electric-log patterns, a slice method was used. The top of the Catahoula was correlated on electric logs and the portion above that formation divided into five equal intervals. The topmost interval was incomplete because of interference by surface casing, and therefore was not used. Percent sand was plotted and sand trends were defined by contouring on maps for each of the four complete intervals.

In general, major sand accumulations overlie those of lower formations, and are interpreted to be fluvial-deltaic deposits. The eastern edge of the strand plain-barrier bar system of south Texas is visible on the western edge of the mapped area. Areas judged to be most favorable as potential uranium host rock were on the margins of major sand bodies where interbedded sand and shale result in decreased permeability, and where organic debris is likely to be found.