Abstract: Slice Technique Applied to Uranium Favorability in Uppermost Tertiary of East Texas and West Louisiana

Leslie Jones

To define favorable areas for uranium mineralization in the upper Tertiary of the East Texas and west Louisiana Gulf Coast, sandstone trends were mapped in four intervals above the Catahoula Formation. Because the difficulty of correlating fluvial deposits is compounded in shallow strata by interference with electric-log patterns by fresh and brackish groundwater, a slice method was used. Electric logs were selected with an 8-mi (13 m) average spacing; the 2,500-ft (760 m) contour on the top of the Catahoula was the cutoff depth. The top of the Catahoula was correlated on the logs, and the part above that formation was divided into five equal intervals. The topmost interval was incomplete because of interference by surface casing, and therefore was not used. Sandstones we e counted and converted to percentage of sandstone; these values were plotted on a map for each of the four complete intervals, and sandstone trends were defined by contouring.

In general, major sandstone accumulations overlie other facies and are interpreted to be fluvial-deltaic deposits; the eastern edge of the strandplain-barrier-bar system of South Texas is visible on the western edge of the mapped area.

Three divisions of percentage of sandstone were used in contouring: 0 to 20, 20 to 50, and more than 50. The contour interval judged to be most favorable as a potential host rock for uranium was the 20 to 50% sandstone division. This percentage was chosen because it indicates areas on the flanks of major sandstone bodies where sandstone is interbedded with shale and permeability decreases, and where organic debris is likely.

AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas