Metchosin Igneous Complex, southern Vancouver Island: Ophiolite stratigraphy developed in an emergent island setting

Massey, N. W. D.

doi:10.1130/0091-7613(1986)14<602:micsvi>2.0.co;2

Cited by 63 publications

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“…Others considered the coastal basalts to be the product of marginal rifting of North America during ridge subduction (Wells et al, 1984;Massey, 1986;Clowes et al, 1987;Snavely, 1987), producing slab window volcanism (Babcock et al, 1992;Thorkelson, 1996;Groome et al, 2003;Haeussler et al, 2003;Breitsprecher et al, 2003). Sheeted dikes in the Metchosin igneous complex of Vancouver Island and locally in the Crescent Formation, along with their transitional chemistry (Massey, 1986), are consistent with marginal rifting, as is the tholeiitic and alkalic volcanism in the Coast Range that continued for 20 m.y.…”

Section: Introductionmentioning

confidence: 84%

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot

et al. 2014

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Siletzia is a basaltic Paleocene and Eocene large igneous province in coastal Oregon, Washington, and southern Vancouver Island that was accreted to North America in the early Eocene. New U-Pb magmatic, detrital zircon, and 40 Ar/ 39 Ar ages constrained by detailed fi eld mapping, global nannoplankton zones, and magnetic polarities allow correlation of the volcanics with the 2012 geologic time scale. The data show that Siletzia was rapidly erupted 56-49 Ma, during the Chron 25-22 plate reorganization in the northeast Pacifi c basin. Accretion was completed between 51 and 49 Ma in Oregon, based on CP11 (CP-Coccolith Paleogene zone) coccoliths in strata overlying onlapping continental sediments. Magmatism continued in the northern Oregon Coast Range until ca. 46 Ma with the emplacement of a regional sill complex during or shortly after accretion. Isotopic signatures similar to early Columbia River basalts, the great crustal thickness of Siletzia in Oregon, rapid eruption, and timing of accretion are consistent with offshore formation as an oceanic plateau. Approximately 8 m.y. after accretion, margin parallel extension of the forearc, emplacement of regional dike swarms, and renewed magmatism of the Tillamook episode peaked at 41.6 Ma (CP zone 14a; Chron 19r). We examine the origin of Siletzia and consider the possible role of a long-lived Yellowstone hotspot using the reconstruction in GPlates, an open source plate model. In most hotspot reference frames, the Yellowstone hotspot (YHS) is on or near an inferred northeast-striking KulaFarallon and/or Resurrection-Farallon ridge between 60 and 50 Ma. In this confi guration, the YHS could have provided a 56-49 Ma source on the Farallon plate for Siletzia, which accreted to North America by 50 Ma. A sister plateau, the Eocene basalt basement of the Yakutat terrane, now in Alaska, formed contemporaneously on the adjacent Kula (or Resurrection) plate and accreted to coastal British Columbia at about the same time. Following accretion of Siletzia, the leading edge of North America overrode the YHS ca. 42 Ma. The voluminous high-Ti basaltic to alkalic magmatism of the 42-35 Ma Tillamook episode and extension in the forearc may be related to the encounter with an active YHS. Clockwise rotation of western Oregon about a pole in the backarc has since moved the Tillamook center and underlying Siletzia northward ~250 km from the probable hotspot track on North America. In the reference frames we examined, the YHS arrives in the backarc ~5 m.y. too early to match the 17 Ma magmatic fl are-up commonly attributed to the YHS. We suggest that interaction with the subducting slab may have delayed arrival of the plume beneath the backarc.

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Section: Introductionmentioning

confidence: 84%

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot

et al. 2014

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“…In Haida Gwaii and the QCB, volcanic rocks may be as old as Jurassic, and younger volcanism is represented by the Masset Formation deposited during Late Oligocene to Early Pliocene time (Anderson and Reichenbach 1991;Hickson 1991). Volcanic units in the TB are primarily known on and offshore as the Eocene-Paleocene Crescent Formation and Metchosin Igneous Complex, and as volcanic units and intrusions on Vancouver Island (MacLeod et al 1977;Muller 1980;Massey 1986;Madsen et al 2006). The significance of the volcanic units in both basins is their timing, potential (or not) for significant heating, and their possible porosity for fluid migrations.…”

Section: Volcanics Minerals and Alterationmentioning

confidence: 99%

Neogene strontium isotope stratigraphy, foraminifer biostratigraphy, and lithostratigraphy from offshore wells, Queen Charlotte Basin, British Columbia, Canada

et al. 2015

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Strontium isotope ages of foraminifers from Early Miocene to Late Pliocene (Neogene) sequences (21.2-3.4 Ma) are reported for the first time from the Queen Charlotte Basin (QCB) in Queen Charlotte Sound, offshore British Columbia. These ages, together with a revised foraminifer biostratigraphy and log data from two offshore wells, provide a high-resolution chronostratigraphy for the southern part of the QCB. The data show thick 1717-2636 m Miocene sequences overlain by much thinner Pliocene and younger units (<240 m). Assessments of foraminifer biofacies indicate common transported neritic and shelf faunas into slope or bathyal environments where changes in basin water depths indicate significant deformation and erosion. Résumé : Des datations isotopiques (strontium) de foraminifères dans des successions (21,2 à 3,4 Ma) du Miocène précoce auPliocène tardif (Néogène) sont rapportées pour la première fois du bassin de la Reine-Charlotte dans le détroit de la ReineCharlotte, au large de la Colombie Britannique. Ces âges, joints à une biostratigraphie des foraminifères révisée et des données de diagraphies de deux puits au large, fournissent une chronostratigraphie à haute définition pour la partie sud du bassin de la Reine-Charlotte.

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“…This complex dips approximately 30 • to the north-northeast (Massey, 1986) and is bounded to the north by the Leech River fault (Fig. 1), which separates it from the Pacific Rim and Wrangellia terranes.…”

Section: Leech River Faultmentioning

confidence: 99%

Constraining fault interpretation through tomographic velocity gradients: application to northern Cascadia

Ramachandran

2012

Solid Earth

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Abstract. Spatial gradients of tomographic velocities are seldom used in interpretation of subsurface fault structures. This study shows that spatial velocity gradients can be used effectively in identifying subsurface discontinuities in the horizontal and vertical directions. Three-dimensional velocity models constructed through tomographic inversion of active source and/or earthquake traveltime data are generally built from an initial 1-D velocity model that varies only with depth. Regularized tomographic inversion algorithms impose constraints on the roughness of the model that help to stabilize the inversion process. Final velocity models obtained from regularized tomographic inversions have smooth three-dimensional structures that are required by the data. Final velocity models are usually analyzed and interpreted either as a perturbation velocity model or as an absolute velocity model. Compared to perturbation velocity model, absolute velocity models have an advantage of providing constraints on lithology. Both velocity models lack the ability to provide sharp constraints on subsurface faults. An interpretational approach utilizing spatial velocity gradients applied to northern Cascadia shows that subsurface faults that are not clearly interpretable from velocity model plots can be identified by sharp contrasts in velocity gradient plots. This interpretation resulted in inferring the locations of the Tacoma, Seattle, Southern Whidbey Island, and Darrington Devil's Mountain faults much more clearly. The Coast Range Boundary fault, previously hypothesized on the basis of sedimentological and tectonic observations, is inferred clearly from the gradient plots. Many of the fault locations imaged from gradient data correlate with earthquake hypocenters, indicating their seismogenic nature.

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Metchosin Igneous Complex, southern Vancouver Island: Ophiolite stratigraphy developed in an emergent island setting

Cited by 63 publications

References 0 publications

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot

Neogene strontium isotope stratigraphy, foraminifer biostratigraphy, and lithostratigraphy from offshore wells, Queen Charlotte Basin, British Columbia, Canada

Constraining fault interpretation through tomographic velocity gradients: application to northern Cascadia

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