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Three late Paleozoic, angular unconformities, each tightly constrained in age by biostratigraphy, are exposed in Carlin Canyon, Nevada. These record deformation as well as erosion. Folding associated with these deformation events is roughly coaxial; all three sets of fold axes trend northeast. Each unconformity represents tectonic disruption of the middle part of the western North American margin between the times of the initiation of the Antler orogeny (Late Devonian-Early Mississippian) and the Permian-Triassic Sonoma orogeny. This paper focuses on one of these unconformities in the Middle Pennsyivanian--the C6 unconformity--and the deformation and age constraints associated with it. Our data from Carlin Canyon yield detailed glimpses of how the Antler foreland evolved tectonically in Mississippian and Pennsylvanian time. Middle Pennsylvanian (Desmoinesian) northwest-southeast contraction resulted in thin-skinned folding and faulting, uplift, and erosion. These data require reinterpretation of the tectonic setting at the time of the Ancestral Rocky Mountains orogeny and suggest that plate convergence on the west side of the continent played a significant role in late Paleozoic tectonics of the North American continent. Keywords: tectonics, stratigraphy, structure, Great Basin, Nevada, Pennsylvanian Ancestral Rocky Mountains.

Stratigraphic analyses in central and eastern Nevada reveal the importance of a deformation event in middle Mississippian time that caused widespread deformation, uplift, and erosion. It occurred between middle Osagean and late Meramecian time and resulted in deposition of both synorogenic and postorogenic sediments. The deformation resulted in east-west shortening, expressed as east-vergent folding and east-directed thrusting; it involved sedimentary rocks of the Antler foredeep as well as strata associated with the Roberts Mountains allochthon. A latest Meramecian to early Chesterian unconformity, with correlative conformable lithofacies changes, postdates this deformation and occurs throughout Nevada. A tectonic highland--created in the middle Mississippian and lasting into the Pennsylvanian and centered in the area west and southwest of Carlin, Nevada--shed sediments eastward across the Antler foreland, burying the unconformity. Postorogenic strata are late Meramecian to early Chesterian at the base and are widespread throughout the Great Basin. The tectonism therefore occurred 20 to 30 m.y. after inception of the Late Devonian Antler orogeny, significantly extending the time span of this orogeny or representing a generally unrecognized orogenic event in the Paleozoic evolution of western North America. We propose a revised stratigraphic nomenclature for Mississippian strata in Nevada, based on detailed age control and the recognition of unconformities. This approach resolves the ambiguity of some stratigraphic names and emphasizes genetic relationships within the upper Paleozoic section. We take advantage of better stratigraphic understanding to propose two new stratigraphic units for southern and eastern Nevada: the middle Mississippian Gap Wash and Late Mississippian Captain Jack Formations. Keywords: Paleozoic, tectonics, stratigraphy, Antler, foreland, lithostratigraphy.

This paper presents algorithm for solving large-scale polynomial (nonlinear) zero-one programming problems. The procedure incorporates a mixture of pseudo-Boolean concepts and time-proven implicit enumeration procedures. Significant savings in the time required to obtain optimal solutions results from the use of a minimum cover to analyze the future effect of a particular implicit enumeration iteration. Additional improvement is obtained through the use of a term ranking strategy to control the arborization of the implicit enumeration process. Computational experience demonstrates that this algorithm can reduce the magnitude of the computer solution time for large problems from several minutes to a matter of a few seconds. [ABSTRACT FROM AUTHOR]

Three late Paleozoic, angular unconformities, each tightly constrained in age by biostratigraphy, are exposed in Carlin Canyon, Nevada. These record deformation as well as erosion. Folding associated with these deformation events is roughly coaxial; all three sets of fold axes trend northeast. Each unconformity represents tectonic disruption of the middle part of the western North American margin between the times of the initiation of the Antler orogeny (Late Devonian—Early Mississippian) and the Permian—Triassic Sonoma orogeny. This paper focuses on one of these unconformities in the Middle Pennsylvanian—the C6 unconformity—and the deformation and age constraints associated with it. Our data from Carlin Canyon yield detailed glimpses of how the Antler foreland evolved tectonically in Mississippian and Pennsylvanian time. Middle Pennsylvanian (Desmoinesian) northwest-southeast contraction resulted in thin-skinned folding and faulting, uplift, and erosion. These data require reinterpretation of the tectonic setting at the time of the Ancestral Rocky Mountains orogeny and suggest that plate convergence on the west side of the continent played a significant role in late Paleozoic tectonics of the North American continent. [ABSTRACT FROM AUTHOR]

Abstract: Volcanic-ash beds within fossiliferous strata of the southern Uralian foredeep of Russia have been dated by the high-precision ID-TIMS U–Pb zircon method, to constrain the age of the Carboniferous–Permian transition. The stratigraphic section exposed at the Usolka locality, an auxiliary stratotype for the Carboniferous–Permian boundary, contains a detailed multi-taxa biostratigraphy with a well-resolved boundary succession tied to the Global Stratotype Section and Point (GSSP) at Aidaralash Creek (Kazakhstan). Four tuffs bracketing the Carboniferous–Permian transition in the Usolka section closely constrain the age of the boundary to 298.90+0.31/−0.15 Ma (2σ), including both analytical and stratigraphic uncertainty. These data substantially improve the calibration of the geologic time scale in the Late Paleozoic, and presage the radiometric age resolution possible for the late Carboniferous and early Permian stages through continued analysis of ash beds in the southern Urals stratotypes. By stabilizing the numeric age for the base of the Permian, these data also provide an important link between the timing of Permo-Carboniferous glaciation in Gondwana and its far-field climatic and sedimentological consequences in Euramerica. [Copyright &y& Elsevier]