Structural Analysis of the Horn Area, Bighorn Mountains, Wyoming

Palmquist, John C.

doi:10.1130/0016-7606(1967)78[283:saotha]2.0.co;2

Cited by 13 publications

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“…I have previously studied the Horn area (Palmquist, 1965(Palmquist, , 1967. These earlier papers emphasized the petrology of the Precambrian core (1965) and analyzed the internal structure of the crystalline rocks and their role in influencing Laramide deformation (1967).…”

Section: Horn Areamentioning

confidence: 99%

“…Thus, a crude first approximation of the Horn block would be to think of its upper surface as an unevenly raised trap door. The structural draping of the cover rocks was described and mapped previously A' (Palmquist, 1967). Even though the basement was described as deforming en bloc, cross sections were drawn (1967, PI. 2) with the basement surface bending smoothly and conformably with the overlying bedding.…”

Section: Structure Of the Horn Blockmentioning

confidence: 99%

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Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Palmquist

1978

Geological Society of America Memoirs

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Two areas in the Big Horn Mountains are given as examples of the beauty and simplicity of the drape-folding-over-basement-block model of structural interpretation. The Piney Creek thrust is interpreted as an uplifted fault block with sedimentary strata draped over its edges. Structural cross sections of the Horn area show how sedimentary layers are continuously folded over a faulted basement.In both areas, the role of a ductile stratigraphic unit, the Gros Ventre shale of Cambrian age, is important in partially decoupling the basement from the overlying sedimentary veneer and in providing a slide surface for gravity phenomena. Gravity glide masses probably are more widespread than is generally recognized in the foreland province and should be considered a characteristic element of the foreland tectonic style.The construction of three-dimensional models of the basement surface, based on detailed geologic mapping, and the comparison of observed structures in the sedimentary cover rocks with experimental draping over the model are effective tools for gaining a mechanical understanding of the development of structures in the foreland province. on July 7, 2015 memoirs.gsapubs.org Downloaded from 132 JOHN C. PALMQUIST 108° 107°

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Section: Horn Areamentioning

confidence: 99%

Section: Structure Of the Horn Blockmentioning

confidence: 99%

Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Palmquist

1978

Geological Society of America Memoirs

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“…Structurally "positive" areas have historically been referred to as arches and/or uplifts. This distinction has been problematic and very Palmquist, 1967Fig. 6 n = 55 Hoppin et al, 1965Fig.…”

Section: Laramide Beltmentioning

confidence: 99%

Structural inheritance and the role of basement anisotropies in the Laramide structural and tectonic evolution of the North American Cordilleran foreland, Wyoming

Bader

2018

Lithosphere

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The Laramide belt of the North American Cordillera is a thickskinned orogen that continues to garner attention due to many unresolved ambiguities, particularly in the subsurface. Recent seismic studies provide a better understanding of Laramide tectonism at deep crustal levels. However, mechanisms for deformation accommodation in the upper crust remain unclear. A structural/tectonic analysis of Precambrian fabrics and structural grain of basement-cored Laramide arches and uplifts in Wyoming using only previously collected data, along with a hypothesis on the potential role of these features in Laramide orogenesis, is presented. This work provides evidence for the presence of Neoarchean convergence zones dominantly directed from the SW-NE toward the Wyoming Province forming NNW anisotropies. In addition, regional compressional forces from convergence formed WNW-and NE-striking conjugate shears. Precambrian basement fabrics characterize all three directions of major anisotropy, and they likely have a complex history of deformation since the Precambrian, most recently, during the Laramide orogeny. This Precambrian deformation system was likely a fundamental tectonic control in Laramide arch/uplift formation in Wyoming. During the Laramide orogeny, reactivation of anisotropies occurred throughout Laramide contraction, forming somewhat symmetrical, but discrete zones of transpression, displaced along a SW-NE-directed Laramide deformational front. Reverse-left oblique-slip faults developed from reactivation of WNW fabrics and, where connected, acted as relay zones, facilitating major arch development along NNWstriking faults. Internal controls for Laramide orogenesis in the upper crust are likely related to these basement anisotropies, which may link the evolution of foreland arches at deeper crustal levels to surface structures.

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“…Hose (1954) mentioned the allanite occurrence and listed some of the minerals present. The geology of the Horn area has been studied by Palmquist (1965Palmquist ( , 1967. The area was visited by Sargent in 1958 who prepared a detailed geologic map and studied the mineralogy of the allanite occurrence (Sargent, 1960).…”

Section: Introductionmentioning

confidence: 99%

“…Armbrustmacher visited the area briefly in 1976 and further sampled the allanite occurrence. Palmquist (1965Palmquist ( , 1967 and the Horn area has been placed in structural perspective by Hoppin and Jennings (1971). Contacts between foliated marble and all other rock types are commonly sharp and even.…”

Section: Introductionmentioning

confidence: 99%

Structural Analysis of the Horn Area, Bighorn Mountains, Wyoming

Cited by 13 publications

References 0 publications

Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Structural inheritance and the role of basement anisotropies in the Laramide structural and tectonic evolution of the North American Cordilleran foreland, Wyoming

Allanite-bearing calc-silicate rocks, southern Bighorn Mountains, Wyoming; geologic setting and resources of thorium, uranium, and rare-earth elements

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