Fluvial Architecture of Jurassic Uranium-Bearing Sandstones, Colorado Plateau, Western United States

Summary

Vanadium- and uranium-bearing sandstones of the Salt Wash Member of the Morrison Formation in south-western Colorado were deposited in a fluvial system that contained a range of channel types. Broad and deep low-sinuosity streams, which were the principal drainage elements, deposited dip-elongate sandstone units. Amalgamation of individual sand bodies resulted in multilateral sandbelt geometry of the lower and upper intervals of the Salt Wash. Minor components of the fluvial system were meandering tributaries of the low-sinuosity streams and crevasse channel and associated splays formed during flooding of the trunk and tributary system.

The Slick Rock uranium district is located in the zone of convergence of smaller streams into trunk rivers. The trunk streams are characterized by individual depositional units stacked into two zones of higher sandstone content. The northernmost of these axes strongly influenced the pattern of migration and concentration of uranium. Significant ore deposits in the district are developed within and along the margins of the axis, which is principally composed of low-sinuosity stream deposits. Excellent downdip interconnectedness of these sandstones made them the major conduits of uraniferous ground-water flow. Smaller deposits are contained within meandering stream sediments. Crevasse splay sequences are essentially barren. Vertical interconnectedness between multi-storied depositional units results in local stacking of mineral deposits.