Paradox Formation of Eastern Utah and Western Colorado

Abstract

The Paradox formation consists of gypsum, anhydrite, and salt, interbedded with shale, sandstone, and limestone. It is the oldest rock exposed in several anticlines in eastern Utah and western Colorado and has been found in a number of wells in the same region. The occurrences indicate much movement of materials, apparently due to the relatively plastic character of salt deposits, and the relationships and true thickness are difficult to determine. Actual thickness in wells exceeds 6,000 feet, but the maximum original thickness may not have been more than about 2,000 feet. The Paradox formation is believed to be conformable with the overlying Hermosa formation and unconformable on the underlying Mississippian beds, though normal contacts have not been observed. The format on contains a few fossil plants, invertebrates, and conodonts which agree in indicating a lower Pennsylvanian age, though the writers infer that the Paradox is wholly older than the Hermosa formation. It is suggested that the Paradox formation occupies an elongated basin southwest of the Uncompahgre uplift and that it thins out southward at Elk Ridge, Utah; westward at San Rafael Swell, Utah; eastward at the Uncompahgre uplift. It is also suggested that the saliferous beds constituting the Weber shales northeast of the Uncompahgre uplift occupy another basin essentially contemporaneous with that occupied by the Paradox formation, though perhaps not connected with it.