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Claire A Currie - One of the best experts on this subject based on the ideXlab platform.
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location location location the variable lifespan of the Laramide Orogeny
Geology, 2017Co-Authors: Peter Copeland, Claire A Currie, Timothy F Lawton, Michael A. MurphyAbstract:The Laramide Orogeny had a spatially variable lifespan, which we explain using a geodynamic model that incorporates onset and demise of flat-slab subduction. Laramide shortening and attendant uplift began in southeast California (USA) at ca. 90 Ma, swept to the northeast to arrive in the Black Hills of South Dakota (USA) at ca. 60 Ma, and concluded in South Dakotawithin ∼10 m.y. During subsequent slab rollback, the areal extent of Laramide deformation decreased as the eastern edge of active deformation retreated to the southwest rapidly from ca. 55 to 45 Ma and more slowly from ca. 45 to 40 Ma, with deformation ultimately ceasing in the southwestern part of the orogen at ca. 30 Ma. Geodynamic modeling of this process suggests that changes in the strength of the North America plate and densifcation of the Farallon plate played important roles in controlling the areal extent of the Laramide orogen and hence the lifespan of the orogenic event at any particular location in western North America.
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farallon plate dynamics prior to the Laramide Orogeny numerical models of flat subduction
Tectonophysics, 2016Co-Authors: Sibiao Liu, Claire A CurrieAbstract:Abstract The Laramide Orogeny (~ 80–50 Ma) was an anomalous period of mountain-building in the western United States that occurred more than 1000 km inboard of the Farallon Plate subduction margin. It is widely believed that this Orogeny is coincident with a period of flat (subhorizontal) subduction. However, the factors that caused the Farallon Plate to evolve from a normal (steep) geometry to flat subduction are not well understood. Three proposed factors are: (1) a westward (trenchward) increase in North America motion, (2) an increased slab suction force owing to the presence of thick Colorado Plateau lithosphere, and (3) subduction of a low-density oceanic plateau. This study uses 2D upper mantle scale numerical models to investigate these factors. The models show that trenchward continental motion is the primary control on subduction geometry, with decreasing slab dip as velocity increases. However, this can only create low-angle subduction, as the Farallon Plate was old (> 100 Myr) and denser than the mantle. A transition to flat subduction requires: (1) subduction of a buoyant oceanic plateau that includes an 18-km-thick crust that does not undergo metamorphic densification and an underlying depleted harzburgite layer, and (2) a slab break-off at the landward side of the plateau. The break-off removes the dense frontal slab, and flat subduction develops as the buoyant plateau deflects the slab upward. The slab suction force has only a minor effect on slab flattening, but the thickness of the Colorado Plateau lithosphere controls the depth of the flat slab. With a continental velocity of 4 cm/yr and a 400-km-wide oceanic plateau, flat subduction develops within 15 Ma after plateau subduction. The flat slab underthrusts the continent at ~ 200 km depth, eventually extending > 1500 km inboard of the trench.
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are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america
Earth and Planetary Science Letters, 2011Co-Authors: Claire A Currie, Christopher BeaumontAbstract:Abstract Diamond-bearing Cretaceous kimberlites of western North America were emplaced 1000–1500 km inboard of the Farallon plate subduction margin and overlap with the development of the Western Interior Seaway, shut-down of the Sierra Nevada arc, and the Laramide Orogeny. These events are consistent with a decrease in subduction angle along much of the margin, which placed the subducted Farallon plate in close proximity to the continental interior at the time of kimberlite magmatism. Our numerical models demonstrate that low-angle subduction can result from high plate convergence velocities and enhanced westward motion of North America. Further, rapid subduction allows hydrous minerals to remain stable within the cool interior of the subducting plate to more than 1200 km from the trench. Destabilization of these minerals provides a fluid source that can infiltrate the overlying material, potentially triggering partial melting and kimberlite/lamproite magmatism.
Richard F. Livaccari - One of the best experts on this subject based on the ideXlab platform.
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isotopic evidence for preservation of cordilleran lithospheric mantle during the sevier Laramide Orogeny western united states
Geology, 1993Co-Authors: Richard F. Livaccari, Frank V PerryAbstract:It has been inferred that Sevier-Laramide flat subduction imparted a large basal shear traction force to the overriding North American plate, resulting in Laramide Rocky Mountain foreland deformation and significant thinning of Cordilleran lithosphere. Additional inferred consequences include regional refrigeration of Cordilleran crust and suppression of synorogenic extensional collapse. Nd isotopic data from Cenozoic mafic volcanic rocks indicate that normal-thickness lithospheric mantle was preserved beneath the Cordilleran craton from Precambrian to late Cenozoic time. Therefore, Cordilleran lithosphere was not thinned significantly, and extensional collapse of orogenically thickened crust was not suppressed by refrigeration. Analogy with the South American Cordillera suggests that flat subduction does not apply significant shear stress to the base of overriding plate lithosphere beyond the fore-arc region and therefore does not mechanically thin overriding plate lithosphere (except in the fore-arc region). The principal result of flat subduction was enhanced mechanical coupling between the underriding and overriding plates along the fore-arc region. This increased the horizontal end load, due to relative plate convergence, placed on the North American plate. Horizontal end-load stress was transmitted laterally across both (1) a hinterland that had attained maximum crustal thickness and (2) the rigid Colorado Plateau into the Laramide Rocky Mountain foreland. Early Tertiary waning of plate-convergence rates then allowed radial extensional collapse of the southern Cordilleran region to drive the Colorado Plateau block northward, resulting in late Laramide Rocky Mountain foreland deformation.
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Role of crustal thickening and extensional collapse in the tectonic evolution of the Sevier-Laramide Orogeny, western United States
Geology, 1991Co-Authors: Richard F. LivaccariAbstract:The effects of crustal thickening and extensional collapse of continental crust, combined with variations in plate-convergence forces, provide a coherent explanation for evolution of the Cretaceous-early Tertiary Sevier-Laramide Orogeny. Crustal thickening of the Sevier-Laramide hinterland region was triggered by the combination of compressive plate-convergence forces and subduction-induced conductive heating of the crust. Eastward progradation of the locus of Sevier-Laramide deformation through time reflects the progressive widening of the region of crustal thickening. The region of maximum crustal thickening migrated outward until about 80 to 75 Ma, when it encountered excessively strong lithosphere of the Colorado Plateau. The locus of deformation was then transmitted laterally across both a hinterland that had attained maximum crustal thickness and the rigid Colorado Plateau, into the Laramide Rocky Mountain foreland. An episode of vigorous extensional collapse of orogenically thickened crust affected the southern Cordillera between about 75 and 35 Ma. Early Tertiary waning of plate-convergence rates and continued subduction-induced conductive heating of thickened crust allowed extensional collapse along the southern Cordillera region to drive the Colorado Plateau block northward. The result was the late Laramide phase of Rocky Mountain foreland deformation. Because of this, compressive deformation in the central and southern Laramide Rocky Mountain region continued through Eocene time, rather than ceasing at 56 Ma, as it did in the northern Cordillera.
Kelin Wang - One of the best experts on this subject based on the ideXlab platform.
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thermal modelling of the Laramide Orogeny testing the flat slab subduction hypothesis
Earth and Planetary Science Letters, 2003Co-Authors: Joseph M. English, Stephen T. Johnston, Kelin WangAbstract:Abstract The Laramide Orogeny is the Late Cretaceous to Palaeocene (80–55 Ma) orogenic event that gave rise to the Rocky Mountain fold and thrust belt in Canada, the Laramide block uplifts in the USA, and the Sierra Madre Oriental fold and thrust belt in Mexico. The leading model for driving Laramide orogenesis in the USA is flat-slab subduction, whereby stress coupling of a subhorizontal oceanic slab to the upper plate transmitted stresses eastwards, producing basement-cored block uplifts and arc magmatism in the foreland. The thermal models presented here indicate that arc magma generation at significant distances inboard of the trench (>600 km) during flat-slab subduction is problematic; this conclusion is consistent with the coincidence of volcanic gaps and flat-slab subduction at modern convergent margins. Lawsonite eclogite xenoliths erupted through the Colorado Plateau in Oligocene time are inferred to originate from the subducted Farallon slab, and indicate that the Laramide flat-slab subduction zone was characterised by a cold thermal regime. Thermal modelling indicates that this regime can be produced by flat-slab subduction of old (>∼50 Myr) oceanic lithosphere at high convergence rates. In the Canadian and Mexican portions of the Laramide orogen, the coeval development of a magmatic arc within 300 km of the trench refutes the existence of flat-slab subduction in these regions. It is proposed that subduction of an oceanic plateau/aseismic ridge may have overcome the negative buoyancy inherent in old oceanic lithosphere and resulted in a spatially restricted zone of flat-slab subduction in the USA. These findings cast doubt on the flat-slab model as a primary means of driving Laramide orogenesis along its entire length, and instead point to the need for an alternative mechanism for Cordilleran-wide Laramide orogenesis.
Christopher Beaumont - One of the best experts on this subject based on the ideXlab platform.
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are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america
Earth and Planetary Science Letters, 2011Co-Authors: Claire A Currie, Christopher BeaumontAbstract:Abstract Diamond-bearing Cretaceous kimberlites of western North America were emplaced 1000–1500 km inboard of the Farallon plate subduction margin and overlap with the development of the Western Interior Seaway, shut-down of the Sierra Nevada arc, and the Laramide Orogeny. These events are consistent with a decrease in subduction angle along much of the margin, which placed the subducted Farallon plate in close proximity to the continental interior at the time of kimberlite magmatism. Our numerical models demonstrate that low-angle subduction can result from high plate convergence velocities and enhanced westward motion of North America. Further, rapid subduction allows hydrous minerals to remain stable within the cool interior of the subducting plate to more than 1200 km from the trench. Destabilization of these minerals provides a fluid source that can infiltrate the overlying material, potentially triggering partial melting and kimberlite/lamproite magmatism.
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paleotemperature history of two transects across the western canada sedimentary basin constraints from apatite fission track analysis
Bulletin of Canadian Petroleum Geology, 1999Co-Authors: Dale R Issler, Christopher Beaumont, Sean D Willett, Raymond A Donelick, Alexander M GristAbstract:ABSTRACT The results of Apatite Fission Track (AFT) analysis for Cretaceous, Paleozoic and Precambrian borehole samples along two major transects through the Western Canada Sedimentary Basin (WCSB) are reviewed here. The northern transect crosses the Peace River Arch (PRA) and extends approximately 700 km from northeast British Columbia to the Alberta-Saskatchewan border northeast of Fort McMurray; the southern transect through central Alberta extends from the edge of the disturbed belt near Rocky Mountain House to the Alberta-Saskatchewan border north of Cold Lake. Sample AFT age and length data show a wide range in the degree of annealing due to the complicated thermal history of the basin and require interpretation through use of a quantitative model. A temperature-dependent fission track annealing model and a controlled random search technique were used to determine sample thermal histories from measured AFT parameters. Many of the Cretaceous samples along the PRA transect appear to have been deposited with effectively zero fission track age, implying a contemporaneous volcanic source for the apatite or rapid exhumation of the source area. Fully annealed samples yield an estimate of 60 Ma for the time of maximum temperature and inferred maximum burial. Maximum AFT paleotemperatures and maximum paleoburial depths (estimated from coal moisture data) were used to estimate paleogeothermal gradient distributions at 60 Ma. For the central Alberta transect, paleogeothermal gradients increase systematically from approximately 20°C/km near the deformation front in the southwest to as high as 60°C/km in the up-dip northeastern portion of the WCSB near the cratonic edge of the basin. Present geothermal gradients show a similar overall pattern but with a narrower range of values (~30°-45°C/km). For the PRA transect, paleogeothermal gradients are elevated in the oil sands region to the east (35°-60°C/km) and in the deep basin to the west (35°-40°C/km). The temporal and spatial variations in geothermal gradient are probably best explained by thermal disturbances caused by regional paleofluid flow across the WCSB near the end of the Laramide Orogeny. RESUME Les resultats de l'analyse des traces de fission de l'apatite (TFA) pour des echantillons de forage du Cretace, du Paleozoique et du Precambrien le long de deux profils majeurs traversant le bassin sedimentaire de l'ouest du Canada (BSOC) sont mis en revue. Le profil du nord traverse l'arche de Peace River (APR) et s'etend approximativement sur 1 Geological Survey of Canada Contribution no. 1998224. End_Page 475------------------------ 700 km, du nord-est de la Colombie-Britannique jusqu'a la frontiere Alberta-Saskatchewan, au nord-est de Fort McMurray; le profil du sud traverse le centre de l'Alberta, de la bordure de la ceinture de deformation a Rocky Mountain House jusqu'a la frontiere Alberta-Saskatchewan, au nord de Cold Lake. L'age de TFA d'echantillon et les donnees de longueur montrent une grande variation du degre de recuit, du a une histoire thermique compliquee dans le bassin et requiert une interpretation par le biais d'un modele quantitatif. Un modele de recuit, dependant de la temperature, des traces de fission et une technique de recherche aleatoire controlee, ont ete utilises pour determiner les histoires thermiques des echantillons a partir de parametres TFA. Plusieurs des echantillons du Cretace, recueillis le long du profil APR, semblent s'etre deposes avec des ages effectifs zero de traces de fission, ce qui implique une source volcanique pour l'apatite ou un exhumation rapide a la region source. Des echantillons completement recuits produisent une estimation de 60 Ma pour la periode de temperature maximum et le maximum infere d'enfouissement. Les paleo-temperatures maximales TFA et les profondeurs de paleoenfouissement maximales (estimees par des donnees d'humidite du charbon) ont ete utilisees pour estimer les distributions de gradient paleo-geothermique a 60 Ma. Pour le profil du centre de l'Alberta, le gradient paleo-geothermique s'accroit systematiquement d'approximativement 20°/km pres du front de deformation au sud-ouest jusqu'a 60°C/km dans la section en amont-pendage au nord-est du bassin sedimentaire de l'Ouest canadien, pres de la marge cratonique du bassin. Les gradients geothermiques actuels montrent dans l'ensemble un patron similaire mais avec une gamme de valeurs plus etroite (~35°-40°C/km). Dans le cas du profil APR, les gradients geothermiques sont eleves dans la region des sables bitumineux a l'est (~35°-60°C/km) et dans la partie profonde du bassin a l'ouest (35-40°C/km). Les variations temporelles et spatiales du gradient geothermique sont probablement le mieux expliquees par les perturbations thermiques causees par l'ecoulement regional de paleo-fluides a travers le bassin sedimentaire de l'Ouest canadien, vers la fin de l'orogenie Laramide. Traduit par Lynn Gagnon
Frank V Perry - One of the best experts on this subject based on the ideXlab platform.
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isotopic evidence for preservation of cordilleran lithospheric mantle during the sevier Laramide Orogeny western united states
Geology, 1993Co-Authors: Richard F. Livaccari, Frank V PerryAbstract:It has been inferred that Sevier-Laramide flat subduction imparted a large basal shear traction force to the overriding North American plate, resulting in Laramide Rocky Mountain foreland deformation and significant thinning of Cordilleran lithosphere. Additional inferred consequences include regional refrigeration of Cordilleran crust and suppression of synorogenic extensional collapse. Nd isotopic data from Cenozoic mafic volcanic rocks indicate that normal-thickness lithospheric mantle was preserved beneath the Cordilleran craton from Precambrian to late Cenozoic time. Therefore, Cordilleran lithosphere was not thinned significantly, and extensional collapse of orogenically thickened crust was not suppressed by refrigeration. Analogy with the South American Cordillera suggests that flat subduction does not apply significant shear stress to the base of overriding plate lithosphere beyond the fore-arc region and therefore does not mechanically thin overriding plate lithosphere (except in the fore-arc region). The principal result of flat subduction was enhanced mechanical coupling between the underriding and overriding plates along the fore-arc region. This increased the horizontal end load, due to relative plate convergence, placed on the North American plate. Horizontal end-load stress was transmitted laterally across both (1) a hinterland that had attained maximum crustal thickness and (2) the rigid Colorado Plateau into the Laramide Rocky Mountain foreland. Early Tertiary waning of plate-convergence rates then allowed radial extensional collapse of the southern Cordilleran region to drive the Colorado Plateau block northward, resulting in late Laramide Rocky Mountain foreland deformation.
