Stratigraphy of the Yellowjacket Formation of east-central Idaho

Lopez, David A.

doi:10.3133/ofr811088

Cited by 15 publications

(37 citation statements)

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“…northern Beaverhead Mountains (Ruppel and Lopez, 1984), and because strata of the formation are folded, commonly into overturned folds (Lopez, 1981;Ruppel, 1980) that geometrically require a basal detachment.…”

Section: Several Large Normal Faults Between Railroad Canyon and Petementioning

confidence: 99%

Contraction and extension faults in the southern Beaverhead Mountains, Idaho and Montana

Skipp¹

1985

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Geologic mapping of 340 square miles (884 square kilometers) in the southern Beaverhead Mountains demonstrates that the area is a segment of the Mesozoic to early Tertiary Cordilleran thrust belt, and a northward continuation of the Idaho-Wyoming thrust salient. Five thrust plates are bounded by major west-dipping, low-angle folded thrusts that juxtapose older strata over younger, and are characterized by east-verging concentric folds, frontal ramp anticlines, and transverse tear faults. The five thrust plates, each with a distinctive stratigraphic sequence, are, in descending structural order: Hawley Creek, Fritz Creek, Cabin, Medicine Lodge, and Tendoy. The Cabin thrust plate locally includes Precambrian (Archean(?)) basement crystalline rocks along its leading edge. These crystalline rocks probably were part of an older Precambrian block uplift cut by the eastward directed Cabin thrust. Extension faults with youngest movements ranging in age from early Eocene to Holocene offset the five thrust plates. The Divide Creek extension fault zone, along which middle Paleozoic stratigraphic section is deleted, probably is of early Eocene age. Miocene to Holocene basin-range faults offset older structures, and loci of the younger faults have shifted westward through time. Thrusts and thrust plates identified in the study area also make up a large part of the central and northern Beaverhead Mountains. The Cabin thrust plate is the most extensive of these. IX The redefined Cabin thrust is more than 125 miles (200 kilometers) long, has two major lateral ramps, has Archean(?) crystalline rocks along a 48-mile (75-kilometer) segment of its leading edge in central parts of the mountains, and Middle Proterozoic Yellowjacket Formation and overlying Lemhi Group rocks in northern parts. The Cabin plate includes Archean(?) through Lower Triassic rocks in the central Beaverheads. In the northern Beaverheads, rocks of the Yellowjacket Formation and the Lemhi Group have been thrust over Belt Supergroup rocks creating a structural culmination of Proterozoic rocks in east-central Idaho. The foreland that was overridden by the easterly transported Cabin and Medicine Lodge thrust plates was deformed by northwest to southeast directed reverse faults that probably were formed and partly eroded before the thrust plates arrived in Late Cretaceous (Maestrichtian(?)) time.

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Section: Several Large Normal Faults Between Railroad Canyon and Petementioning

confidence: 99%

Contraction and extension faults in the southern Beaverhead Mountains, Idaho and Montana

Skipp¹

1985

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“…1). As the term is currently used, however, the formation includes virtually all of the dark-colored, quartz-rich metasedimentary rocks of Middle Proterozoic age in east-central Idaho (see, for example, Lopez, 1981). The formation is best known as host to the stratiform Co deposits of the Blackbird Mining District.…”

Section: Introductionmentioning

confidence: 99%

Some geochemical features of the Blackbird and Jackass zones of the Yellowjacket Formation (middle Proterozoic) in east-central Idaho

Connor¹

1991

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Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards nor with the North American stratigraphic codes. Although these data have been used by the U.S. Geological Survey and have been successfully imported into a number of data base and spreadsheet programs, no warranty, expressed or implied, is made by the USGS as to how successfully or accurately the data can be imported into any specific application software running on any specific hardware platform. The fact of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith.

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“…Continuity of the stratigraphic succession from the Lemhi Range to the Salmon River Mountains, as well as subdivision of the units within the Salmon River Mountains, was accomplished in part through geologic mapping in the Salmon River Mountains to determine continuity of structural features there with those of the Lemhi Range Previous investigations revealed that many of the metasandstones in Mesoproterozoic formations of central Idaho are arkosic (Lopez, 1981;. In the Lemhi Range, these formations include the Mesoproterozoic Big Creek, Apple Creek, and Gunsight Formations of the Lemhi Group .…”

Section: Discussionmentioning

confidence: 99%

“…In the Lemhi Range, these formations include the Mesoproterozoic Big Creek, Apple Creek, and Gunsight Formations of the Lemhi Group . In the Salmon River Mountains, arkosic metasandstones are found in rocks now correlated with the Lemhi Group (Tysdal, 2000a) but formerly assigned to the Mesoproterozoic Yellowjacket Formation (Lopez, 1981;. In both ranges, as well as in the Beaverhead Mountains, arkosic metasandstones of the Gunsight Formation contain abundant plagioclase as well as potassium feldspar .…”

Section: Discussionmentioning

confidence: 99%

“…Although rocks of the Lemhi Group have been metamorphosed to greenschist facies, with metamorphic biotite common in the Salmon River Mountains, clastic metasedimentary textures and structures are evident (Lopez, 1981;). Comparison of the major-oxide composition of siltite in the more highly metamorphosed rocks (biotite-grade greenschist facies) of the Salmon River Mountains with the composition of siltite in the less metamorphosed (chlorite-grade greenschist facies) rocks of the same unit in the Lemhi Range indicates that modification of the original chemical composition is probably minimal (Lindsey and others, 2002).…”

Section: Discussionmentioning

confidence: 99%

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Correlation, sedimentology, structural setting, chemical composition, and provenance of selected formations in Mesoproterozoic Lemhi Group, central Idaho

Tysdal¹,

Lindsey²,

Taggart³

2003

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Stratigraphy of the Yellowjacket Formation of east-central Idaho

Cited by 15 publications

References 0 publications

Contraction and extension faults in the southern Beaverhead Mountains, Idaho and Montana

Contraction and extension faults in the southern Beaverhead Mountains, Idaho and Montana

Some geochemical features of the Blackbird and Jackass zones of the Yellowjacket Formation (middle Proterozoic) in east-central Idaho

Correlation, sedimentology, structural setting, chemical composition, and provenance of selected formations in Mesoproterozoic Lemhi Group, central Idaho

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