20:
74:, a major geologic feature of the area. The central and western portions of the zone are believed to be about 1.1 to 3.3 billion years old. The central part of the zone lacks Archean rock, however, leading at least one group of scientists to speculate that it was formed very late in the
100:
The Great Falls tectonic zone was first identified in 1985. Geologists originally believed the zone was part of the
Wyoming craton, but now conclude that it is distinct from it. There is continuing controversy over whether the region is a shear zone or
235:
Harms, Tekla A.; Brady, John B.; Burger, H. Robert; and Cheney, John T. "Advances in the
Geology of the Tobacco Root Mountains, Montana, and Their Implications for the History of the Northern Wyoming Province."
198:
Mueller, Paul A.; Heatherington, Ann L.; Kelly, Dawn M.; Wooden, Joseph L.; and Mogk, David W. "Paleoproterozoic Crust Within the Great Falls
Tectonic Zone: Implications for the Assembly of Southern Laurentia."
109:
were both considered sutures, but debate remains open on the point. At least one group of geologists has concluded the zone represents the closure of an ocean basin. The zone lacks
279:
O'Neill, J. Michael and Lopez, David A. "Character and
Regional Significance of the Great Falls Tectonic Zone, East-Central Idaho and West-Central Montana."
240:
Special Papers, Volume 377. John B. Brady, H. Robert Burger, John T. Cheney, and Tekla A. Harms, eds. Boulder, Colo.: Geological
Society of America, 2004.
212:
O'Neill, J. Michael and Lo, David A. "Character and
Regional Significance of Great Falls Tectonic Zone, East-Central Idaho and West-Central Montana."
171:
Boerner, D.E.; Craven, J.A.; Kurtz, R.D.; Ross, G.M.; and Jones, F.W. "The Great Falls
Tectonic Zone: Suture or Intracontinental Shear Zone?"
349:
2 (1993); Hoy, T. "The
Purcell Supergroup in Southeastern British Columbia: Sedimentation, Tectonics and Stratiform Lead-Zinc Deposits." In
105:, and the role the zone played in the formation of the North American continent. At one time, both the Great Falls Tectonic Zone and the
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378:
334:
265:
245:
71:
362:
Hearn Jr., B. Carter. "The
Homestead Kimberlite, Central Montana, USA: Mineralogy, Xenocrysts, and Upper-Mantle Xenoliths."
345:
Foster, F. and Childs, J.F. "An
Overview of Significant Gold Lode Systems in Montana, and Their Regional Geologic Setting."
313:
Metallogeny of Mesoproterozoic Sedimentary Rocks in Idaho and Montana—Studies by the Mineral Resources Program, 2004–2007.
126:
401:
396:
327:
Whence the Mountains?: Inquiries Into the Evolution of Orogenic Systems: A Volume in Honor of Raymond A. Price.
118:
81:
The Great Falls tectonic zone has been periodically active since the Proterozoic, and possibly as late as the
296:
Gifford, Jennifer N.; Foster, David A.; Mueller, Paul A.; Mogk, D.W.; Kamenov, George D.; and Probst, Kelly.
411:
90:
416:
130:
94:
316:
U.S. Geological Survey Open-File Report 2007–1280. Washington, D.C.: U.S. Geological Survey, 2007.
43:
298:
Plutonic Imaging: A View into the Lower Crust and Upper Mantle of the Great Falls Tectonic Zone.
295:
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or electromagnetic signatures which would allow scientists to conclude that it was generated by
93:. However, it is believed that the tectonic zone controlled the geologic development of nearby
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54:. The zone is an area about 100 miles (150 km) wide extending from the southwestern
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63:
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16:
Major intracontinental shear zone between the Hearne craton and Wyoming craton
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times. Square Butte, Shaw Butte, Crown Butte and the other structures of the
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301:
2008 Joint GSA, SSSA-ASA-CSSA, and GCAGS Annual Meeting. October 7, 2008.
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59:
47:
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117:. There is significant evidence that the zone has been periodically
151: – Craton in the west-central United States and western Canada
55:
369:
77:1-4 (September 2004); Alt, David and Hyndman, Donald W.
238:
Precambrian Geology of the Tobacco Root Mountains, Montana.
145: – Craton forming the geological core of North America
353:
Special Paper 25. Geological Association of Canada, 1982.
371:
Northwest Exposures: A Geologic Story of the Northwest.
325:
Sears, James W.; Harms, Tekla A.; and Evenchick, C.A.
281:
American Association of Petroleum Geologists Bulletin.
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Boulder, Colo.: Geological Society of America, 2007.
62:border across Montana to the northwestern Montana-
129:lie astride the tectonic zone near the city of
8:
256:Rogers, John James William and Santosh, M.
50:Eon which form part of the North American
23:Location of the Great Falls Tectonic Zone.
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260:New York: Oxford University Press, 2004.
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373:Missoula, Mont.: Mountain Press, 1995.
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85:. Little of the zone is visible due to
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174:Canadian Journal of Earth Sciences
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72:Great Falls of the Missouri River
347:Explorations in Mining Geology.
258:Continents and Supercontinents.
89:cover, the exception being the
1:
351:Precambrian Sulfide Deposits.
127:Adel Mountains Volcanic Field
70:border. It is named for the
31:is a major intracontinental
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407:Precambrian United States
29:Great Falls Tectonic Zone
311:O'Neill, J.M., editor.
24:
203:30:2 (February 2002).
143:North American craton
91:Little Belt Mountains
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95:basins and subbasins
402:Geology of Montana
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111:gravity anomalies
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107:Vulcan structure
76:Paleoproterozoic
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397:Archean geology
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149:Wyoming Craton
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41:Wyoming craton
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37:Hearne craton
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412:Suture zones
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283:69:3 (1985).
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178:35:2 (1998).
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68:North Dakota
64:Saskatchewan
35:between the
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417:Shear zones
131:Great Falls
123:Precambrian
87:Phanerozoic
391:Categories
219:69 (1985).
156:References
115:subduction
33:shear zone
52:continent
201:Geology.
137:See also
83:Holocene
60:Montana
48:Archean
46:of the
377:
365:Lithos
333:
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121:since
103:suture
78:Era.
56:Idaho
375:ISBN
331:ISBN
262:ISBN
242:ISBN
39:and
27:The
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66:-
58:-
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