Queen Charlotte basin and Coast Mountains: Paired belts of subsidence and uplift caused by a low-angle normal fault

Rohr, Kristin M. M.; Currie, Lisel D.

doi:10.1130/0091-7613(1997)025<0819:qcbacm>2.3.co;2

Cited by 29 publications

(20 citation statements)

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“…Oblique subduction of the Kula/Farallon plate [ Engebretson et al , 1985; Stock and Molnar , 1988; Crawford et al , 1999], along with thermal weakening of the crust [ Dostal et al , 2001], likely contributed to the collapse of the Cordilleran orogenic belt and the development of numerous extensional grabens in central and southern British Columbia [e.g., Dostal et al , 2001] during the Eocene, continuing through the Miocene. Basin development occurred coevally with alkaline basaltic magmatism near the margin of the North American plate [ Rohr and Currie , 1997; Dostal et al , 2001; Edwards and Russell , 1999, 2000] and the emplacement of N–S trending mafic dike swarms [ Irving et al , 1992]. …”

Section: Discussionmentioning

confidence: 99%

“…A regional tectonic synthesis indicates that the onset of dextral transform motion along the Queen Charlotte fault system and intermittent periods of highly oblique divergence and convergence between the North American and Pacific plates in the early Eocene [ Engebretson et al , 1985; Stock and Molnar , 1988] drove continental extension in western Canada. This period of extension has been documented by the opening of large, normal fault‐bounded basins [ Rohr and Dietrich , 1992; Rohr and Currie , 1997; Dostal et al , 2001] and widespread mafic magmatism since the Eocene.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have focused on Eocene–Quaternary basalts (and similar mafic rocks) that are widely distributed throughout the western Canadian Cordillera. Basalts are preserved as large plateau‐forming lava flows (e.g., 3300 km 3 Chilcotin Group Basalts) [ Bevier , 1983], small‐volume cinder cone and fissure eruptions [e.g., Carignan et al , 1994; Francis and Ludden , 1990], and dikes that intrude the igneous rocks of the CMB and metamorphic rocks of the Cordilleran terranes [ Irving et al , 1992; Rohr and Currie , 1997; Crawford et al , 2005; Rusmore et al , 2005]. Increased mafic magmatism beginning at ∼48 Ma corresponds with the initial stages of transform motion along the Queen Charlotte Fairweather fault system (Figure 1) and intermittent periods of highly oblique divergence and convergence between the North American and Pacific plates [ Engebretson et al , 1985; Stock and Molnar , 1988; Irving et al , 1992].…”

Section: Introductionmentioning

confidence: 99%

“…Increased mafic magmatism beginning at ∼48 Ma corresponds with the initial stages of transform motion along the Queen Charlotte Fairweather fault system (Figure 1) and intermittent periods of highly oblique divergence and convergence between the North American and Pacific plates [ Engebretson et al , 1985; Stock and Molnar , 1988; Irving et al , 1992]. The opening and subsidence of large extensional basins during the Miocene [ Rohr and Dietrich , 1992; Rohr and Currie , 1997] occurred concurrently with shear distribution in the North American plate [ Rohr and Currie , 1997], increased mantle heat flow [ Edwards and Russell , 2000], and the emplacement of mafic dike swarms that trend perpendicularly to the direction of extension [ Irving et al , 1992]. …”

Section: Introductionmentioning

confidence: 99%

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Isotopic and geochemical evidence for a recent transition in mantle chemistry beneath the western Canadian Cordillera

Manthei¹,

Ducea²,

Girardi³

et al. 2010

J. Geophys. Res.

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[1] New petrologic, geochemical, and isotopic data are reported from a suite of mafic dike and lava flow samples collected from sites within the western Canadian Cordillera. Samples range in age from Eocene to Quaternary and document a significant transition in mantle chemistry that occurred sometime after 10 Ma. Eocene to late Miocene basalts emplaced as dikes within the Coast Mountains Batholith contain abundant hornblende, are enriched in large ion lithophile elements (LILE) (Ba, Rb, K), have negative high field strength element (HFSE) (Nb, Ta) anomalies, and were likely derived from lithospheric mantle ( 87 Sr/ 86 Sr = 0.70353-0.70486; e Nd = +2.5 to +5.7) that was stabilized after the cessation of arc magmatism in the area. By contrast, Quaternary lava flows have lower LILE concentrations, positive Nb-Ta anomalies, and were likely generated by upwelling asthenosphere ( 87 Sr/ 86 Sr = 0.70266-0.70386; e Nd = +7.4 to +8.8) or at least a mantle source with different chemical and isotopic characteristics. A regional comparison of mafic rocks from western Canada that are also Eocene to Quaternary in age indicates that the transition in mantle chemistry after 10 Ma was pervasive and widespread and was not limited to the present study area. This transition occurred $40 Ma after the cessation of Cordilleran arc magmatism in central British Columbia, suggesting that large-scale transitions in mantle chemistry beneath magmatic arcs may occur on the order of tens of millions of years after the final subduction of oceanic lithosphere, in this case as a result of lithospheric thinning by continental extension.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Isotopic and geochemical evidence for a recent transition in mantle chemistry beneath the western Canadian Cordillera

Manthei¹,

Ducea²,

Girardi³

et al. 2010

J. Geophys. Res.

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“…Prior to 40 Ma, the plate boundary was a subduction zone, with either the Pacific or the Kula plate being subducted (Hyndman and Hamilton, 1993). Since 40 Ma, the plate boundary has been primarily transcurrent, with likely, but poorly constrained, episodes of both transpression and transtension (Rohr and Currie, 1997;Smith et al, 2003). Timing of the initiation of the current episode of contraction has long been debated.…”

Section: Tectonic Setting and Morphology Of The Qcf Systemmentioning

confidence: 99%

An Abrupt Transition in the Mechanical Response of the Upper Crust to Transpression along the Queen Charlotte Fault

Tréhu¹,

Scheidhauer²,

Rohr³

et al. 2015

Bulletin of the Seismological Society of America

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The Queen Charlotte Fault (QCF) is a major strike-slip fault that forms the boundary between the Pacific and North American plates from 51°to 58°N. Near 53.2°N, the angle of oblique convergence predicted by the Mid-Ocean Ridge VELocity (MORVEL) interplate pole of rotation decreases from > 15°in the south to < 15°in the north. South of 53.2°N, the convergent component of plate motion results in the formation of a 40 km wide terrace on the Pacific plate west of QCF and earthquakes with thrust mechanisms (including the 2012 Haida Gwaii earthquake sequence) are observed. North of 53.2°N, in the primary rupture zone of the M 8.1 strike-slip earthquake of 1949, the linear terrace disappears, and topography of the continental slope west of the QCF is characterized by a complex pattern of ridges and basins that trend obliquely to the primary trace of the QCF. Deformation within the Pacific plate appears to occur primarily through strike-slip faulting with a minor thrust component on secondary synthetic faults. The orientations of these secondary faults, as determined from seismic reflection and bathymetric data, are consistent with the reactivation of faults originally formed as ridge-parallel normal faults and as thrust faults formed parallel to the QCF south of the bend at 53.2°N and subsequently translated to the north. We suggest that an oblique convergence angle of 15°represents a critical threshold separating distinct crustal responses to transpression. This result is consistent with theoretical and analog strain models of transpressive plate boundaries. The sharpness of this transition along the QCF, in contrast to purely continental transform boundaries, may be facilitated by the relatively simple structure of oceanic crust and the presence of pre-existing, optimally oriented faults in the young Pacific plate.

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An Overview of the 28 October 2012 Mw 7.7 Earthquake in Haida Gwaii, Canada: A Tsunamigenic Thrust Event Along a Predominantly Strike-Slip Margin

Cassidy

Rogers

Hyndman

2014

Pure Appl. Geophys.

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Queen Charlotte basin and Coast Mountains: Paired belts of subsidence and uplift caused by a low-angle normal fault

Cited by 29 publications

References 0 publications

Isotopic and geochemical evidence for a recent transition in mantle chemistry beneath the western Canadian Cordillera

Isotopic and geochemical evidence for a recent transition in mantle chemistry beneath the western Canadian Cordillera

An Abrupt Transition in the Mechanical Response of the Upper Crust to Transpression along the Queen Charlotte Fault

An Overview of the 28 October 2012 Mw 7.7 Earthquake in Haida Gwaii, Canada: A Tsunamigenic Thrust Event Along a Predominantly Strike-Slip Margin

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