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Large-Scale Fold Domain

The Large-Scale Fold Domain is defined by the presence of large-scale, generally north-trending, broad to tight, symmetrical to asymmetrical, variable amplitude and wavelength folds. These folds have wavelengths of as much as several miles and lengths of over 45 miles. These include folds in the Adobe, Pinon, Fish Creek, northern Pancake, northern Monitor, and northern Antelope Ranges, Elko Hills, Leach, Delano, southern Independence, Diamond, and Butte Mountains, Sulphur Spring Range, Buck Mountain-Bald Mountain, Alligator Ridge, Maverick Springs, Medicine, and northern Cherry Creek Ranges, Currie Hills, Dolly Varden Mountains, southern Pequop Range, and northern White Pine Range. These folds are described in some detail in the Structural Setting and Range Structure portions of this volume.

This Domain encloses folds of various ages that are the result of more than one deformational event. The Domain overlaps both the Antler and Golconda-Antler Thrust Domains, and may partially overlap the Low-Angle Normal Fault Domain. Folds related to Devonian through Mississippian Antler and Permian through Triassic Golconda thrusting, as well as local folds related to major extension along low-angle and associated high-angle normal faults, and perhaps even to the mysterious Sevier thrusting are contained within the domain.

The general lack of Mesozoic rocks and broad Tertiary volcanic and sedimentary cover make it difficult to determine the age of a given fold or fold set. A post-Devonian, and in many cases a post-Mississippian lower age boundary can be assigned to these folds. The upper age boundary is difficult to determine but can be shown to be post-Permian in many areas, and post-Triassic or Cretaceous in local exposures. In several ranges, Oligocene volcanics unconformably overlie the folds and show no evidence of internal deformation indicating Pre-Oligocene deformation.

Tight and locally overturned folds are present along the leading edge of the Roberts Mountains thrust and locally the Golconda thrust in the Independence, Adobe, Pinon, and Sulphur Spring Ranges, and Diamond Mountains, with typically open and gentle folds to the east in the Buck Mountain-Bald Mountain, Butte Mountains, and Currie Hills area. Folding in the northern White Pine, southern Pequop, and northern Pancake Ranges appears to be related to nearby extensional low-angle and high-angle normal faults.

All of these folds are segmented to varying degrees by high-angle normal and minor reverse faults. The most highly segmented blocks within the Large-Scale Fold Domain are present in the Fish Creek, northern Cherry Creek and northern White Pine Ranges, the Dolly Varden Mountains, Medicine Range, and the area north of the Leach Mountains. Along the overlap with the Antler-Golconda Thrust Domain these folds are associated with imbricate thrust faults in the Sulphur Spring and Pinon Ranges, and the Independence Mountains.

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Last modified: 09/12/06