The stratal architecture of the upper Ely Limestone and Mormon Gap Formation (Pennsylvanian-early Permian) in western Utah reflects the interaction of icehouse sea-level change and tectonic activity in the distal Antler-Sonoma foreland basin. Eighteen physically and biostratigraphically corelated stratigraphic sections provide a database for tracing Permo-Carboniferous boundary strata over a north-south distance of 60 km. These formations comprise 14 unconformity-bounded depositional sequence: three in the upper Ely (UE1-UE3) and 11 in the Mormon Gap Formation (MG1-MG11). Conodont and fusulinid faunas provide precise biostratigraphic information for a number of parasequences in the upper Ely and Mormon Gap formations. This paleontological information clarifies the tectonostratigraphic evolution of the distal foreland basin (study area) and permits correlation with events in the proximal foreland (Nevada) and with depositional sequences in the North American midcontinent. The stratigraphic succession is divided into three depositional intervals (I-III) with distinctive differences in constituent facies and facies stacking patterns, the regional continuity of cycles, the relative abundance of dolomite and limestone, calculated sediment accumulation rates, and the frequency and inferred duration of sequence-bounding hiatuses. These reflect the interaction of high-frequency sea-level change on an intermittently subsiding distal foreland basin. Subsidence is generally continuous during the Bashkirian through middle Moscovian (Interval I) and again during the Artinskian (Interval II). During the late Moscovian through Sakmarian stages (Interval III), subsidence rates dropped and sedimentation occurred mainly in consequence of second-order sea-level rise associated with the highstand of the Lower Absaroka II seas. Strata in the distal foreland are bounded by low-relief disconformities of variable duration in stark contrast to the angular unconformities and intensely deformed tectonostratigraphic domains that characterize the proximal foreland basin in north-central Nevada.



College and Department

Physical and Mathematical Sciences; Geological Sciences



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Mormon Gap, conodont, fusulinid, Pennsylvanian, Permian, Western Utah, Ely