Abstract: Sandstone Depositional Systems in Uraniferous Sandstones of Colorado Plateau
Robert G. Young
Sandstone-type uranium deposits long have been exploited on the Colorado Plateau of Colorado, Utah, New Mexico, and Arizona from at least 20 different stratigraphic units ranging in age from Pennsylvanian to Miocene. Some deposits seem to be intrinsic to their host sandstones, but others appear to have been introduced along fractures or collapses, and still others are indeterminate.
Host sandstones for uranium are products of three depositional systems--fluvial, wind, and tidal. The fluvial-system hosts predominate almost to exclusion of the other two. Depositional environments within the fluvial system are flood plain and paludal. Swamp, meandering-channel, and braided-channel subenvironments are present in both environments. Deposits in sandstones of the wind and tidal systems are relatively unimportant and apparently are due primarily to migration of uraniferous solutions along permeable zones from nearby fluvial-host deposits. In the wind system the common host is a dune sandstone, whereas, in the tidal system, tidal-channel sandstones commonly are the hosts.
An attempt to portray the dispersal patterns of uranium-bearing sandstones in the three major producing units on the Colorado Plateau show that those of the Chinle Formation display a meandering-channel and associated swamp pattern, and those of the Salt Wash and Westwater Canyon Members of the Morrison Formation show a braided channel-alluvial fan pattern.
Depositional-system and environmental data are valuable in predicting uranium trends and deposits as illustrated by Salt Wash sandstone patterns on the Uncompahgre uplift in western Colorado.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC