Abstract

Host to extensive uranium and vanadium mineralization. Sandstones deposited in a complex fluvial system. Facies analysis of the Slick Rock Uranium District documents three major sandstone facies interbedded within a sequence of mudstones, siltstones, and thin sandstones. Large-scale trough cross-bedded facies is the dominant sandstone. It represents deposition in northeast-flowing, low-sinuosity trunk streams. The second most abundant sandstone facies is medium- to small-scale trough crossbedded sandstone within lensoid, fining-upward cycles. Vertical decrease in the scale of structures and variable paleocurrent orientations are characteristic of these units. This facies represents the point bars of meandering streams that acted as tributaries to the low-sinuosity trunk channels. The third sandstone facies, interpreted as crevasse-splay deposits, contains coarsening-upward sandstone packages with variable structures and a distinctive convex geometry. The mudstone, siltstone, and thin sandstone facies averages 50 percent of the member, and represents well-drained floodplain deposits, shallow ephemeral lakes, and abandoned channel fills. Analysis leads to the conclusion that the Salt Wash Member is a fan apron marginal to an alluvial fan or coalesced fan complex. Sandstones that transect the district represent depositional axes of this fluvial system.--Modified journal abstract.

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