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southwestern Montana

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Journal Article
Journal: Geology
Published: 01 November 1990
Geology (1990) 18 (11): 1107–1110.
...J. Michael O'Neill; Christopher J. Schmidt; Paul W. Genovese Abstract The front of the Cordilleran fold and thrust belt in western Montana follows the disturbed belt in the north, merges with the southwest Montana transverse zone in the west-central part of the region, and in southwestern Montana...
Published: 01 January 1994
DOI: 10.1130/SPE287-p5
... In Montana, Wyoming, North and South Dakota, and Minnesota, Cretaceous strata are preserved in the asymmetric Western Interior foreland basin. More than 5,200 m (17,000 ft) of Cretaceous strata are present in southwestern Montana, less than 300 m (1,000 ft) in eastern South Dakota...
Journal Article
Published: 03 June 2025
Journal of the Geological Society (2025) jgs2024-252.
...Kevin H. Mahan; Cailey B. Condit; Rebecca M. Flowers; Liam Courtney-Davies; Jae Bridges; Keneni Godana The northern Madison Range is one of several exposures in SW Montana that record tectonism associated with the 1.78-1.72 Ga Big Sky orogeny. Studies show that exposed 1.7 Ga crustal levels were...
Journal Article
Journal: Geosphere
Published: 10 October 2023
Geosphere (2023) 19 (6): 1616–1639.
... décollement and the Selkirk allochthon ( Brown et al., 1992 ; Norlander et al., 2002 ; Gibson et al., 2008 ). Many of the features described in the previous paragraph are present in the footwall of the Anaconda metamorphic core complex of southwestern Montana, the most recently documented metamorphic...
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Journal Article
Published: 01 January 2023
The Journal of Geology (2023) 131 (1): 75–95.
...Francis Ö. Dudás; Nilanjan Chatterjee; Michael Krol Abstract The Lone Mountain laccolith in the Madison Range of southwestern Montana consists of andesitic adakite that intruded at 49.0 ± 0.2 Ma. Mineral thermobarometry indicates that the magma began to crystallize at pressure-temperature ( P - T...
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Journal Article
Journal: Geosphere
Published: 04 November 2022
Geosphere (2022) 18 (6): 1783–1803.
...Cole T. Gardner; Emily S. Finzel; Justin A. Rosenblume; David M. Pearson Abstract The middle Cretaceous Blackleaf Formation records the first major transgressionregression of the Western Interior Seaway into the southwestern Montana retroforeland basin. Although Blackleaf sedimentology is well...
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Journal Article
Journal: PALAIOS
Published: 16 April 2020
PALAIOS (2020) 35 (4): 165–174.
...LUCAS S. ANTONIETTO; LISA E. PARK BOUSH; ROY E. PLOTNICK; ALYCIA L. STIGALL ABSTRACT The Renova Formation is a Paleogene sedimentary sequence from southwestern Montana that was deposited in a more extensive basin dominated by mid- to high altitude streams and small-lake paleoenvironments...
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Journal Article
Journal: AAPG Bulletin
Published: 01 May 2018
AAPG Bulletin (2018) 102 (5): 793–815.
...Anna S. Phelps; Michael H. Hofmann; Bruce S. Hart ABSTRACT This study describes the sedimentology and stratigraphy of the Devonian–Mississippian Sappington Formation in exceptional outcrop exposures in southwestern Montana. The goal was to assess the extent to which these outcrops could be used...
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Journal Article
Journal: Geosphere
Published: 20 June 2017
Geosphere (2017) 13 (4): 1285–1309.
...Theresa M. Schwartz; Stephan A. Graham Abstract In southwestern Montana (SWMT), Paleogene strata that are preserved in the Sage Creek basin were deposited during the transition from late-stage Sevier-Laramide compressional tectonism to extensional reactivation of the northern Rocky Mountain region...
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Journal Article
Journal: Interpretation
Published: 31 December 2014
Interpretation (2015) 3 (1): T25–T41.
...Jose Pujol; Mervin J. Bartholomew; Andrew Mickelson; Michael Bone Abstract We collected shallow reflection data in southwestern Montana, USA, across a 5.4-m-high tectonic scarp. The goal was to image the normal fault associated with the scarp, observed in an adjacent trench. Processing of the data...
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Series: GSA Field Guide
Published: 01 January 2014
DOI: 10.1130/2014.0037(08)
EISBN: 9780813756370
... Abstract We summarize the geologic settings, generalized geology, and inferred conditions of talc formation for two major deposits in southwestern Montana. Imerys Talc operates the Yellowstone Mine in the Gravelly Range. Barretts Minerals Inc., a subsidiary of Minerals Technologies Incorporated...
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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...
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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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Series: SEPM Special Publication
Published: 01 January 2008
DOI: 10.2110/pec.08.89.0147
EISBN: 9781565762244
... strata in east-central Idaho and southwestern Montana. Lithofacies Stratigraphic Expression Sedimentary Structures Fossils/Allochems Depositional Environment; Estimated Water Depth Cycle Expression Occurrence Deep Subtidal Carbonate ps = parasequences Bedded mudstone...
Journal Article
Published: 01 January 2007
Rocky Mountain Geology (2007) 42 (2): 157–174.
...Karl S. Kellogg; Stephen S. Harlan Abstract Detailed 40 Ar/ 39 Ar dating and paleomagnetic analysis of dacite porphyry sills and dikes that intrude Cretaceous sedimentary rocks in the northern Madison Range in southwestern Montana show that Laramide shortening was essentially complete by ∼69 Ma...
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Journal Article
Published: 27 January 2004
Canadian Journal of Earth Sciences (2004) 41 (1): 63–72.
... on older rocks. This area, which we call the AMCC, is the manifestation of early Tertiary ductile–brittle crustal extension superimposed on the multiplely and complexly deformed Archean to Mesozoic rocks of the region. Southwestern Montana is underlain, in part, by crystalline basement rocks...
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Published: 01 January 2002
DOI: 10.1130/0-8137-2359-0.29
Journal Article
Published: 01 January 2002
Rocky Mountain Geology (2002) 37 (1): 13–30.
... Foundation. This is contribution J-200118 of the Montana Agricultural Experiment Station. REFERENCES CITED Becker , H. F. , 1959 , A new species of Maahonia from the Oligocene Ruby flora of southwestern Montana : University of Michigan Museum of Paleontology Contributions , v. 15 , p. 33...
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Journal Article
Journal: AAPG Bulletin
Published: 01 August 1996
AAPG Bulletin (1996) 80 (8): 1177–1183.
...T. S. Dyman; J. G. Palacas; R. G. Tysdal; W. J. Perry, Jr.; M. J. Pawlewicz ABSTRACT The middle Cretaceous in southwestern Montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the Western Interior Seaway. In places...
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