Yellowstone in Yukon: The Late Cretaceous Carmacks Group

Johnston, Stephen T.; Wynne, P. J.; Francis, Don; Hart, Craig J.R.; Enkin, Randolph J.; Engebretson, David C.

doi:10.1130/0091-7613(1996)024<0997:yiytlc>2.3.co;2

Cited by 64 publications

(51 citation statements)

References 20 publications

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“…Supporting this conclusion are robust paleomagnetic poles from the ~70 Ma Carmacks volcanic rocks (Johnston et al 1996;Enkin et al 2006a), which although much younger, were located in the same block as the plutonic suites (Figs. 3,5), and were erupted at the approximate latitude of San Francisco.…”

Section: Sevier Eventsupporting

confidence: 58%

“…Another 'slab' farther west and as deep as 1800 km rises westward to connect with the Cascadia subduction and thus represents the Farallon slab at depth, so the separate eastern slab cannot be the Farallon slab (Sigloch et T a n T T a n a n a a n n a a n a n a a e S e (Hart et al 2004a, b;Rasmussen 2013) interpreted to result from failure of the west-dipping North American oceanic plate. Note the abundant remnants of 70 Ma Carmacks volcanic rocks, which in multiple studies, yielded paleolatitudes of San Francisco (Johnston et al 1996;Enkin et al 2006a). As rocks of Selwyn basin, Cassiar platform, and Yukon-Tanana terrane were joined together at 260-253 Ma (Beranek and Mortensen 2011) they are all interpreted to have been located within the Great Basin-Sonora segments of the orogen at 70 Ma and migrated to their present northerly latitude mostly during the early Tertiary.…”

Section: Geophysics Seismic Tomographymentioning

confidence: 99%

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Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

Hildebrand

2014

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Geological evidence, including the presence of two passive margin platforms, juxtaposed and mismatched deformation between North America and more outboard terranes, as well as the lack of rift deposits, suggest that North America was the lower plate during both the Sevier and Laramide events and that subduction dipped westward beneath the Cordilleran Ribbon Continent (Rubia). Terranes within the composite ribbon continent, now present in the Canadian Cordillera, collided with western North America during the 125–105 Ma Sevier event and were transported northward during the ~80–58 Ma Laramide event, which affected the Cordillera from South America to Alaska. New high-resolution mantle tomography beneath North America reveals a huge slab wall that extends vertically for over 1000 km, marks the site of long-lived subduction, and provides independent verification of the westward-dipping subduction model. Other workers analyzed paleogeographic trajectories and concluded that the initial collision took place in Canada at about 160 Ma – a time and place for which there is no deformational thickening on the North American platform – and later farther west where subduction was not likely westward, but eastward. However, by utilizing a meridionally corrected North American paleogeographic trajectory, coupled with the geologically most reasonable location for the initial deformation, the position of western North America with respect to the relict superslab parsimoniously accounts for the timing and extents of both the Sevier and Laramide events. SOMMAIRELes indications géologiques, en particulier la présence de deux marges de plateforme passives, de déformations adjacentes non-conformes entre l’Amérique du Nord et les terranes extérieurs, ainsi que l’absence de gisements de rift, permet de croire que l’Amérique du Nord était la plaque sous-jacente durant les événements de Sevier et de Laramide et que la subduction plongeait vers l’ouest sous le continent rubané de la Cordillères (Rubia). Les terranes du continent rubané composite, maintenant au sein de la Cordillère canadienne, sont entrés en collision avec l’ouest de l’Amérique du Nord durant l’événement Sevier (125-105 Ma), et ont été transportés vers le nord durant l’événement Laramide (~80–58 Ma), laquelle a affecté la Cordillère, de l’Amérique du Sud à l’Alaska. Une nouvelle tomographie haute résolution du manteau sous l’Amérique du Nord montre la présence d’un gigantesque mur de plaques vertical qui s’étend sur 1 000 km, marque le site d’une subduction de longue haleine, et offre une validation indépendante du modèle d’une subduction à pendage vers l’ouest. D’autres chercheurs ont analysé les trajectoires paléogéographiques et conclu que la collision initiale s’est produite au Canada vers 160 Ma – un moment et un endroit sans épaississement par déformation sur la plateforme d’Amérique du Nord – et plus tard plus à l’ouest, là où la subduction n’était vraisemblablement pas vers l’ouest, mais vers l’est. Cela dit, en considérant une trajectoire paléogéographique de l’Amérique du Nord corrigée longitudinalement, avec la position géologique la plus probable de la déformation initiale, la position de la portion ouest de l’Amérique du Nord par rapport aux restes de la super-plaque explique alors facilement la chronologie et l’étendue des épisodes Sevier et Laramide.

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Section: Sevier Eventsupporting

confidence: 58%

Section: Geophysics Seismic Tomographymentioning

confidence: 99%

Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

Hildebrand

2014

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“…Paleomagnetic data implies that large portions of the orogen underwent significant midCretaceous southerly displacements [57], coeval with fold and thrust belt formation within the foreland, widespread dextral strike-slip faulting and voluminous granitic magmatism as far inboard as the eastern limit of Selwyn basin [58]. Paleomagnetic data from Late Cretaceous strata require significant northward translations, relative to the autochthon [59,60] coeval with fold and thrust belt formation in the foreland and oroclinal buckling of the ribbon continent in Alaska [55].…”

Section: Accretionary Orogensmentioning

confidence: 99%

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

Johnston

Borel²

2007

Earth and Planetary Science Letters

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The Cache Creek terrane (CCT) of the Canadian Cordillera consists of accreted seamounts that originated adjacent to the Tethys Ocean in the Permian. We utilize Potential Translation Path plots to place quantitative constraints on the location of the CCT seamounts through time, including limiting the regions within which accretion events occurred. We assume a starting point for the CCT seamounts in the easternmost Tethys at 280 Ma. Using reasonable translation rates (11 cm/a), accretion to the StikiniaQuesnellia oceanic arc, which occurred at about 230 Ma, took place in western Panthalassa, consistent with the mixed Tethyan fauna of the arc. Subsequent collision with a continental terrane, which occurred at about 180 Ma, took place in central Panthalassa, N 4000 km west of North America yielding a composite ribbon continent. Westward subduction of oceanic lithosphere continuous with the North American continent from 180 to 150 Ma facilitated docking of the ribbon continent with the North American plate.The paleogeographic constraints provided by the CCT indicate that much of the Canadian Cordilleran accretionary orogen is exotic. The accreting crustal block, a composite ribbon continent, grew through repeated collisional events within Panthalassa prior to docking with the North American plate. CCT's odyssey requires the presence of subduction zones within Panthalassa and indicates that the tectonic setting of the Panthalassa superocean differed substantially from the current Pacific basin, with its central spreading ridge and marginal outward dipping subduction zones. A substantial volume of oceanic lithosphere was subducted during CCT's transit of Panthalassa. Blanketing of the core by these cold oceanic slabs enhanced heat transfer out of the core into the lowermost mantle, and may have been responsible for the Cretaceous Normal Superchron, the coeval Pacific-centred mid-Cretaceous superplume event, and its lingering progeny, the Pacific Superswell. Far field tensile stress attributable to the pull of the slab subducting beneath the ribbon continent from 180 to 150 Ma instigated the opening of the Atlantic, initiating the dispersal phase of the supercontinent cycle by breaking apart Pangea. Docking of the ribbon continent with the North American plate at 150 Ma terminated the slab pull induced stress, resulting in a drastic reduction in the rate of spreading within the growing Atlantic Ocean.

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“…The Carmacks Group provides a critical paleopole supporting the Baja BC hypothesis on account of its age and trustworthy paleohorizontal-other poles were older, placing less stringent constraints on the timing of northward motion, and most were from intrusives with no paleohorizontal (Marquis and Globerman 1988;Johnston et al 1996;Enkin et al 2006). The restudies confirmed that, compared with cratonic North America (Kent and Irving 2010), paleomagnetic inclinations imply ~3000 km of northward displacement since 70 Ma, placing the Carmacks Group at the latitude of San Francisco during its eruption.…”

mentioning

confidence: 99%

“…Consequently, a Late Cretaceous -early Cenozoic interval of rapid (~12 cm/yr) dextral transpression between the Kula and North American plates interrupted the Farallon-North America subduction regime. Large (~2000 km) poleward displacement (and dextral rotation) of 'Baja British Columbia', or Baja BC, the inter-montane and coastal zones of the Canadian Cordillera, occurred at this time (Beck and Noson 1972;Irving et al 1996;Johnston et al 1996;Enkin 2006;Enkin et al 2006). It came as a revelation to geologists that in a system with constant plate motions, western North America had experienced abrupt yet diachronous changes in tectonic state (Fig.…”

mentioning

confidence: 99%

The Tooth of Time: The North American Cordillera from Tanya Atwater to Karin Sigloch

Hoffman¹

2013

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Yellowstone in Yukon: The Late Cretaceous Carmacks Group

Cited by 64 publications

References 20 publications

Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

The Tooth of Time: The North American Cordillera from Tanya Atwater to Karin Sigloch

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