Paleomagnetism of ocean layers 2 and 3: evidence from the Metchosin Complex, Vancouver Island

Irving, E.; Massey, N. W. D.

doi:10.1016/0031-9201(90)90041-u

Cited by 9 publications

(19 citation statements)

References 21 publications

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“…Third, the Crescent Formation, where sampled in the north, records no significant net rotation or displacement. This concordance agrees with in situ results from the Metchosin Igneous Complex studied by Irving and Massey [1990] and supports their assumption that the entire exposure of the Metchosin is essentially horizontal. Concordance, however, appears anomalous when compared to results from Coast Range exposures to the south.…”

Section: Crescent Even Within Homoclinal Localities To Favor Early supporting

confidence: 90%

“…Whether these basalts were formed on an oceanic plate and were accreted to North America, or are the result of a rift within the western margin of North America has been controversial [Wells et al, 1984;Babcock et al, 1992]. Rotations of the Coast Range basalts increase from none at the north [Beck and Engebretson, 1982;Irving and Massey, 1990; this paper] to as much as 80 ø of net clockwise rotation to the south [Simpson and Cox, 1977;Wells et al, 1985;Beck, 1989b;Wells, 1990] (Figure 1). Wells and Heller [1988] addressed the relative contribution of three proposed rotation mechanisms: rotation during accretion [Simpson and Cox, 1977;Magill et al, 1981;Duncan, 1982], nonrigid dextral shear rotation due to coupling between North America and the obliquely converging Farallon or Kula plates [Beck, 1976[Beck, , 1980Reidel et al, 1984;Sheriff, 1984], and rigid rotation due to differential extension of the Basin and Range Province [Simpson and Cox, 1977;Magill et al, 1981;Frei et al, 1984;Groinrod et al, 1986].…”

Section: Introductionmentioning

confidence: 99%

“…The lack of rotation found in the northern Coast Recent palcomagnetic studies of the upper (subaerial) portion of the Crescent Formation in and near the Olympic Mountains (Figure 2) [Beck and Engebretson, 1982;Purdy, 1987;Warnock, 1989] found apparent rotations, but lacked the broad geographic coverage required to unravel the regional structural and tectonic history. Magnetizations from intrusive rocks of the correlative Metchosin Igneous Complex on southern Vancouver Island (Figure 2) are concordant, but lack local structural control [Irving and Massey, 1990]. The goal of this project was to study the palcomagnetism of the Crescent basalts of the northern Olympic Mountains where better structural control and large areal extent might be sufficient to make sense of the existing ambiguous directions and constrain the emplacement and deformational history of the rocks of the northern Coast Range.…”

Section: Introductionmentioning

confidence: 99%

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Paleomagnetism and tectonics of the Crescent Formation, northern Olympic Mountains, Washington

Warnock¹,

Burmester²,

Engebretson³

1993

J. Geophys. Res.

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A stable prefolding magnetization has been discovered in pillow basalts of the Eocene lower Crescent Formation of the northern Olympic Mountains. The curved outcrop pattern of the Crescent Formation has been the target of several unsuccessful studies to test for oroclinal bending. The success of this study is due, in part, to the development of a small‐diameter electric core drill for sampling the fractured rims of basalt pillows. Thermal demagnetization produced stable endpoints by 580°C in 12 of the 34 sites sampled (large within‐site scatter was common in the remaining sites). Among the accepted sites, within‐site scatter was small and correction for bedding tilt significantly reduced the scatter between sites. The mean paleomagnetic pole for newly sampled pillow basalts (86.4° north latitude, 170.0° east longitude, A95=16.5°) is indistinguishable from the early to middle Eocene pole expected for North America. Including previous results from sites in subaerial basalt of the upper Crescent Formation in and near the easterm Olympic Mountains results in a more regional paleomagnetic pole (80.7° north latitude, 192.0° east longitude, A95 =8.0°, N=46) that shows no significant rotation (0.8° ± 14.4°) or poleward displacement (−3.6 ± 8.5). Analysis of the magnetic mineralogy suggests that the remanence is early, probably primary. The pole, therefore, should be valid for tectonic interpretation of the region. A circular distribution of virtual geomagnetic poles after correction for bedding tilt supports the hypothesis that the northern Crescent Formation experienced deformation due to the rise, in a domelike fashion, of the sediments of the Olympic Core terrane. Erosion of a partial dome open to the west could have produced the curvature seen in the outcrop pattern of the Crescent Formation. The lack of significant rotation of the northernmost Coast Ranges contrasts with the net clockwise rotation seen to the south. The difference could be that irrotational northward translation (paleomagnetically insignificant yet geologically important), driven by oblique convergence, was accommodated by the north‐south trending strike‐slip faults to the east of the Olympic Mountains.

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Section: Crescent Even Within Homoclinal Localities To Favor Early supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Paleomagnetism and tectonics of the Crescent Formation, northern Olympic Mountains, Washington

Warnock¹,

Burmester²,

Engebretson³

1993

J. Geophys. Res.

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“…Both complexes preserve sheeted dikes with similar north-northeast-south-southwest orientations (Fig. 4) that we consider to record the primary extensional direction, because paleomagnetic data from the Metchosin complex demonstrate that it has undergone little to no postaccretion vertical-axis rotation (Irving and Massey, 1990). The implied spreading direction from these dike orientations is west-northwest-east-southeast, and the difference in age between the ca.…”

Section: Tectonic Settingmentioning

confidence: 87%

Age and volcanic stratigraphy of the Eocene Siletzia oceanic plateau in Washington and on Vancouver Island

2017

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Geophysical, geochemical, geochronologic, and stratigraphic observations all suggest that the basalts that underlie western Oregon and Washington (USA), and southern Vancouver Island (Canada) form a coherent terrane of Eocene age, named Siletzia. The total volume of basalt within Siletzia is comparable to that observed in large igneous provinces and several lines of evidence point toward the terrane's origin as an accreted oceanic plateau. However, a thick sequence of continentally derived turbidites, named the Blue Mountain unit, has long been considered to floor the northern part of the terrane and its presence has led to alternative hypotheses in which Siletzia was built on the continental margin. We present new high-precision U-Pb zircon dates from silicic tuffs and intrusive rocks throughout the basaltic basement of northern Siletzia, as well as detrital zircon age spectra and maximum depositional ages for the Blue Mountain unit to help clarify the volcanic stratigraphy of this part of the terrane. These dates show that northern Siletzia was emplaced between 53.18 ± 0.17 Ma and 48.364 ± 0.036 Ma, similar to the age and duration of magmatism in the central and southern parts of the terrane. Turbidites in the basal Blue Mountain unit have maximum depositional ages as young as 44.72 ± 0.21 Ma and are distinctly younger than the basaltic basement that forms Siletzia. This age relationship implies that they were thrust under the terrane after 44.72 ± 0.21 Ma along one or more enigmatic faults. The younger age for these sedimentary rocks no longer requires construction of Siletzia on the continental margin, and we consider our revised stratigraphy to provide further support for the origin of the terrane as an accreted oceanic plateau.

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“…Q, Quaternary; S, Sooke Fm; M1, Sooke Gabbro; M2, Metchosin Volcanics; M3, Catface intrusions. Sample sites this report, 1, 2, 3, 4; Sooke Fm sample sites of Irving and Massey (1990), S1 and S2. Inset map: Location of main map area.…”

Section: Introductionmentioning

confidence: 99%

Paleomagnetism and counterclockwise tectonic rotation of the Upper Oligocene Sooke Formation, southern Vancouver Island, British Columbia

et al. 2008

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The age of the Sooke Formation on the southern coast of Vancouver Island, British Columbia, Canada, has long been controversial. Prior paleomagnetic studies have produced a puzzling counterclockwise tectonic rotation on the underlying Eocene volcanic basement rocks, and no conclusive results on the Sooke Formation itself. We took 21 samples in four sites in the fossiliferous portion of the Sooke Formation west of Sooke Bay from the mouth of Muir Creek to the mouth of Sandcut Creek. After both alternating field (AF) and thermal demagnetization, the Sooke Formation produces a single-component remanence, held largely in magnetite, which is entirely reversed and rotated counterclockwise by 35° ± 12°. This is consistent with earlier results and shows that the rotation is real and not due to tectonic tilting, since the Sooke Formation in this region has almost no dip. This rotational signature is also consistent with counterclockwise rotations obtained from the northeast tip of the Olympic Peninsula in the Port Townsend volcanics and the Eocene–Oligocene sediments of the Quimper Peninsula. The reversed magnetozone of the Sooke sections sampled is best correlated with Chron C6Cr (24.1–24.8 Ma) or latest Oligocene in age, based on the most recent work on the Liracassis apta Zone molluscan fauna, and also a number of unique marine mammals found in the same reversed magnetozone in Washington and Oregon.

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Paleomagnetism of ocean layers 2 and 3: evidence from the Metchosin Complex, Vancouver Island

Cited by 9 publications

References 21 publications

Paleomagnetism and tectonics of the Crescent Formation, northern Olympic Mountains, Washington

Paleomagnetism and tectonics of the Crescent Formation, northern Olympic Mountains, Washington

Age and volcanic stratigraphy of the Eocene Siletzia oceanic plateau in Washington and on Vancouver Island

Paleomagnetism and counterclockwise tectonic rotation of the Upper Oligocene Sooke Formation, southern Vancouver Island, British Columbia

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