GEOLOGIC RE-EVALUATION OF THE ORIGIN(S) OF THE CARBONATE ROCKS ASSOCIATED WITH THE MOAB VALLEY SALT WALL, SOUTH-CENTRAL UTAH, IN THE LIGHT OF NEWLY EMERGING SALT TECTONICS CONCEPTS

The salt walls and adjacent strata of the Paradox Basin in the Four Corners region are an important repository for natural resources such as petroleum, potash, and uranium and hold considerable potential for H₂ and CO₂ storage. Despite their economic and societal importance, the geologic origin and history of salt diapirism, adjacent minibasin sediment deposition, and fluid flow has not been assessed in the context of a modern salt tectonic conceptual framework. This re-evaluates the origin, age and geologic setting of various carbonate units exposed around the Moab Valley salt wall, located in south-central Utah. The carbonates on the southwest side of the salt wall are distinctly different from those on the northeast side. The southwest side carbonates are meter-thick dolostone beds locally interbedded with dark gray carbonate mudstones typical of outcrops of the Paradox Formation. The carbonates on the northeast side display attributes that are not typical of the Paradox Formation such as isolated pods of microcrystalline, non-fossiliferous dolostone either surrounded by gypsic diapiric caprock or concordant with Triassic Chinle Formation strata.These carbonate units were formerly mapped as Pennsylvanian Paradox Formation implying they are part of the diapiric material originally deposited with the salt. Recent studies of circum-diapir carbonates at other Paradox salt walls indicate several alternative origins including upturned strata of Pennsylvanian-age marine strata of the Paradox Formation forming a megaflap, Triassic lacustrine, Triassic caprock, and recent karst-related carbonates. Initial geologic mapping shows that there are at least three groups of carbonates in the study area: one correlatable to the owl rock member of the Chinle Formation, a second group belonging to the Layered Evaporite Sequence of the Paradox formation and a third group without any stratigraphic correlation to these other formations. Each of these carbonates shows a distinct fabric and stratigraphic context. Further analyses will involve petrography and isotope geochemistry to further clarify the origin of the carbonates.