Geologic mapping (1:24,000 scale) of the Ice Cave Peak quadrangle, Uintah and Duchesne Counties, Utah has produced a better understanding of the geologic structures present in the quadrangle and has increased our understanding of faulting in northeastern Utah. Map units in the quadrangle range in age from late Neoproterozoic to Quaternary and include good exposures of Paleozoic rocks (Mississippian to Permian), limited exposures of Mesozoic rocks, and good exposures of Tertiary strata (Duchesne River Formation and Bishop Conglomerate) deposited during uplift of the Uinta Mountains. Lower Mississippian strata along the south flank of the Uinta Mountains have typically been mapped as Madison Limestone. Our preliminary mapping suggested that the Madison could perhaps be subdivided into an upper unit equivalent to the Deseret Limestone, and a lower unit separated by a phosphatic interval equivalent to the Delle Phosphatic Member of the Deseret Limestone found farther west. Upon further investigation, we propose not extending the use of Deseret Limestone, with the equivalent to the Delle Phosphatic Member at its base, into the south-central Uinta Mountains. Microprobe analysis revealed no phosphorus in thin sections of this unit. Instead, the unit is composed almost entirely of calcite and dolomite. A zone of northwest-trending faults, called the Deep Creek fault zone, occurs mainly east of the Ice Cave Peak quadrangle. However, our mapping shows that this fault zone extends into the quadrangle. These faults are both strike-slip and normal/oblique faults as documented by mapping and kinematic indicators and cut the folded hanging-wall sedimentary rocks above the Uinta Basin-Mountain boundary thrust fault. These faults may be part of an en echelon fault system that is rooted in the Neoproterozoic and reactivated during Laramide deformation above a possible transfer zone between segments of the buried boundary thrust.



College and Department

Physical and Mathematical Sciences; Geological Sciences



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Uinta Mountains, Laramide faulting, Ice Cave Peak



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Geology Commons