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Helena salient

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Journal Article
Journal: GSA Bulletin
Published: 29 September 2023
GSA Bulletin (2024) 136 (5-6): 2256–2280.
...Caden J. Howlett; Gilby Jepson; Barbara Carrapa; Peter G. DeCelles; Kurt N. Constenius Abstract The timing of deformation within and adjacent to the Helena salient of west-central Montana is poorly constrained relative to other segments of the Sevier fold-and-thrust belt. This study presents low...
FIGURES | View All (12)
Series: AAPG Studies in Geology
Publisher: American Association of Petroleum Geologists and Rocky Mountain Association of Geologists
Published: 01 January 2013
DOI: 10.1306/13381690St653574
EISBN: 9781629812632
... Abstract Dating of detrital zircons from well cuttings is a useful technique to constrain stratigraphic ages and structural interpretations in complexly deformed terranes. This technique was applied in the Helena Salient of the Montana Disturbed Belt to determine whether the Norcen, Kimpton...
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Journal Article
Journal: GSA Bulletin
Published: 01 September 2008
GSA Bulletin (2008) 120 (9-10): 1091–1104.
...Stephen S. Harlan; John Wm. Geissman; Stephen C. Whisner; Christopher J. Schmidt Abstract Paleomagnetic and 40 Ar/ 39 Ar data from intermediate composition sills exposed along the southern margin of the Helena salient in southwestern Montana help refine the age of Late Cretaceous contraction...
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Journal Article
Journal: GSA Bulletin
Published: 01 April 1988
GSA Bulletin (1988) 100 (4): 492–499.
...STEVE S. HARLAN; JOHN WM. GEISSMAN; DAVID R. LAGESON; LAWRENCE W. SNEE Abstract Thrust-belt deformation along the eastern edge of the Disturbed Belt in the Helena salient of Montana has not been well dated owing to a lack of syn- or postorogenic strata. In situ paleomagnetic data from alkaline...
Published: 01 January 2004
DOI: 10.1130/0-8137-2383-3(2004)383[173:LACLAT]2.0.CO;2
... Paleocene crustal shortening. The Lewis-Eldorado-Hoadley slab, north of the Lewis and Clark line, rotated about a pole near Helena, Montana, producing the Alberta salient, whereas the Sapphire and Lombard slabs, south of the Lewis and Clark line, rotated about poles located in Idaho, producing the Helena...
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Thermochronological models using zircon (U‐Th)&#x2F;He) from the <span class="search-highlight">Helena</span> <span class="search-highlight">Salient</span> ...
Published: 27 September 2022
Fig. 10. Thermochronological models using zircon (U‐Th)/He) from the Helena Salient area ( Carrapa et al. 2019 ), indicating initial cooling and exhumation of several Precambrian-cored, mountain blocks starting at 100 Ma. (See Fig. 5 for locations of uplifted massifs.) Those authors suggest
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Map showing the tectonic setting of the <span class="search-highlight">Helena</span> <span class="search-highlight">salient</span> of the Montana part ...
Published: 01 September 2008
Figure 1. Map showing the tectonic setting of the Helena salient of the Montana part of the North American Cordilleran orogenic belt. Also shown is the location of the study area in the transverse zone along the southern margin of the salient. Figure modified from Burton et al. (1995) .
Published: 01 January 1988
DOI: 10.1130/MEM171-p319
... Paleomagnetic investigations throughout the overthrust belt in the Wyoming and Helena salients show that buttressing effects of the Rocky Mountain foreland have caused local rotations of thrust sheets along the margins of the salients. Two previous studies of Triassic, Upper Jurassic, and Lower...
Published: 01 January 1988
DOI: 10.1130/MEM171-p171
... rocks on the north in the Helena salient from basement-involved “thick-skinned” thrusts and reverse faults of the Rocky Mountain foreland on the south. This first-order structural boundary is interpreted to be superimposed on a down-to-the-north normal fault zone that marked the southern margin...
Journal Article
Journal: GSA Bulletin
Published: 01 June 1992
GSA Bulletin (1992) 104 (6): 779–785.
...ARTHUR D. JOLLY; STEVEN D. SHERIFF Abstract Near Wolf Creek, Montana, the fold and thrust belt intersects the central Montana trough at the northern edge of the Helena salient. Remanent magnetizations from 18 of 31 paleomagnetic sites in the Late Cretaceous Two Medicine Formation (∼79 Ma) document...
Journal Article
Published: 22 February 2021
Canadian Journal of Earth Sciences (2021) 58 (8): 697–719.
..., a flexural foredeep. In western Nevada, where the Luning–Fencemaker thrust might be a mid-Cretaceous feature, arc and post-collisional plutons occur in proximity. The orogen continues through the Helena salient and Washington Cascades. In British Columbia, rocks of the 130–100 Ma Gambier arc lie west...
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Journal Article
Journal: Economic Geology
Published: 01 September 2013
Economic Geology (2013) 108 (6): 1397–1424.
... to 6 km. The Butte Granite and Boulder batholith were emplaced at 79 to 76 Ma into thrust fault ramps, which later became inactive near Butte as Laramide crustal shortening moved eastward in the Helena salient. The accelerated period of uplift and unroofing is attributed to renewed deformation along...
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Journal Article
Journal: GSA Bulletin
Published: 01 May 2013
GSA Bulletin (2013) 125 (5-6): 961–984.
...Theresa M. Schwartz; Robert K. Schwartz Abstract The Paleogene Renova Formation is the earliest record of postcompressional sedimentation within and adjacent to the Helena Salient of the Cordilleran fold-and-thrust belt in southwestern Montana. Paleocurrent and compositional data from basin-margin...
FIGURES | View All (10)
Journal Article
Journal: Geology
Published: 01 August 2001
Geology (2001) 29 (8): 723–726.
..., and forelandward translation of the Helena salient. Delivery of eroded volcaniclastic detritus from the thickened thrust wedge and accelerated basin subsidence due to thrust loading resulted in accumulation of a thick (4–5 km) sequence of Campanian-Maastrichtian volcaniclastic strata in the foreland basin...
FIGURES
Series: DNAG, Centennial Field Guides
Published: 01 January 1987
DOI: 10.1130/0-8137-5402-X.37
EISBN: 9780813754086
... Abstract The Sawtooth Range is located in northwest Montana in parts of Pondera, Teton, and Lewis and Clark counties. The range is part of the Rocky Mountain fold and thrust belt, or Disturbed Belt, and lies between Glacier National Park to the north and the Helena salient to the south...
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Figure 3. Diagram showing timing of deformational events and magmatism in H...
Published: 01 August 2001
Figure 3. Diagram showing timing of deformational events and magmatism in Helena salient between 84 and 50 Ma. Magmatic activity includes intrusive and eruptive activity as well as production of epiclastic sedimentary deposits. Magmatic activity in western Helena salient includes almost
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Geologic map of west-central Montana, modified from the geologic map of Mon...
Published: 01 September 2013
Fig. 1 Geologic map of west-central Montana, modified from the geologic map of Montana (GM-62, Vuke et al., 2007 ). Laramide base and precious metal mineralization is associated with the batholiths of southwestern Montana. The Boulder batholith is emplaced into the Helena structural salient
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Figure 1. Map of northern U.S. Rocky Mountains from Idaho-Bitterroot bathol...
Published: 01 August 2001
Figure 1. Map of northern U.S. Rocky Mountains from Idaho-Bitterroot batholith to Helena salient, encompassing Boulder batholith. Cross- section vertical exaggeration is 3X. L-ET—Lombard-Eldorado thrust; SWMTZ—southwest Montana transverse (fault) zone
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(A) Generalized tectonic map of the western Montana segment of the Sevier t...
Published: 29 September 2023
, and exposed Precambrian basement, for clarity. Proterozoic features include the Garnet and Perry lines (adapted from Winston, 1986 ). Linear structures of central Montana are adapted from Baker (1991) . (B) Regional geology within and adjacent to the Helena salient. Late K—Late Cretaceous; pЄ—Precambrian.
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Regional geologic map of the Anaconda metamorphic core complex footwall. Re...
Published: 10 October 2023
Figure 3. Regional geologic map of the Anaconda metamorphic core complex footwall. Red rectangle in inset shows location of Figure 3 relative to the Helena salient. Black-outlined rectangle in main panel shows location of the study area. The footwall consists of complexly deformed Mesoproterozoic