Paleomagnetism of small basalt exposures in the West Puget Sound Area, Washington, and Speculations on the accretionary origin of the Olympic Mountains

Beck, Myrl E.; Engebretson, David C.

doi:10.1029/jb087ib05p03755

Cited by 33 publications

(18 citation statements)

References 17 publications

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“…Folding of the Olympic structure into its present broad horseshoe shape ( Fig. 1) may have occurred during accretion (Tabor and Cady 1978b;Beck and Engebretson 1982) or during more recent extension in the Pacific Northwest.…”

Section: Tectonic Styles Compressional Tectonicsmentioning

confidence: 97%

Paleogeographic evolution of the United States Pacific Northwest during Paleogene time

Heller¹,

Tabor²,

Suczek³

1987

Can. J. Earth Sci.

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Paleogeographic reconstructions for Oregon and Washington during Paleogene time illustrate a major transition from a dominantly compressional (prior to middle Eocene time) to an extensional tectonic regime. This transition resulted in the development of three phases of Paleogene basin evolution in the United States Pacific Northwest. During the initial phase, basins formed along the continental margin during collision of oceanic islands. Sediments in these basins were derived from nearby orogenic highlands. The second phase of basin development began in middle Eocene time and consisted of rapid subsidence of individual basins that formed within a broad forearc region. Nonmarine basins that formed during this phase were caused by extension possibly associated with transcurrent faulting. Rapid sedimentation in both marine and nonmarine basins during this time consisted dominantly of sandstone derived from Cretaceous plutonic sources far to the east. The final stage of basin development was the modification of previous basin configurations by the growth of the Cascade volcanic arc, which was initiated in early Oligocene time. The rising Cascade Range diverted streams canying eastem-derived material, thereby reducing overall sedimentation rates in the coastal basins and providing a local source of volcanic detritus.Dans les Ctats de l'Or6gon et de Washington, les reconstitutions palBogCographiques durant le PalCogbne illustrent une pCriode de transition majeure d'un regime de compression tectonique dominante (anterieur i 1'Eocbne moyen) B un rCgime de distension tectonique. Trois phases de 1'Cvolution du bassin palkogbne dans le nord-ouest Pacifique des Etats-Unis sont dues h cette transition. Au cours de la phase initiale, des bassins se formbrent le long de la marge continentale lors de la collision des iles ockaniques. Les saiments dans yes bassins provenaient des hautes terres des monts avoisinants. La seconde phase de dtveloppement du bassin dCbuta i 1'Eocttne moyen, et elle correspond B une subsidence rapide des bassins individuels qui s'ktaient formCs au coeur d'une grande region d'arc frontal. Les bassins continentaux qui se developpbrent durant cette phase doivent leur origine B une extension qui accompagnait probablement un dkcrochement. La sedimentation rapide dans les bassins marins et continentaux i cette Cpoque Ctait dominee par des g k s dCrivCs des &ions nourricsres plutoniques cr6tacCes situCes plus i l'est. L'Ctape final du dCveloppement des bassins fut la modification des configurations des bassins dCjB exitants provoquke par la croissance de l'arc volcanique des Cascades, lequel arc est apparu au dCbut de I'Oligocbne. Le soulbvement de la chaine des Cascades a modifiC la direction d'ecoulement des cours d'eau qui transportaient des matkriaux provenant de l'est, de ce fait rkduisant les taux de sedimentation moyens dans les bassins c6tiers et foumissant une source locale de detritus volcanique.[Traduit par la revue]Can.

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Section: Tectonic Styles Compressional Tectonicsmentioning

confidence: 97%

Paleogeographic evolution of the United States Pacific Northwest during Paleogene time

Heller¹,

Tabor²,

Suczek³

1987

Can. J. Earth Sci.

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“…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%

“…Wells and Heller [1988] concluded that a combination of rotations due to Basin and Range extension and oblique convergence fits the geologic and palcomagnetic data without invoking complicated accretion models. 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].…”

Section: Introductionmentioning

confidence: 99%

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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“…results, and the data from the Crescent Formation to the south, all other rocks on the north flank of the Olympic Peninsula show a counterclockwise rotation. Beck and Engebretson [66] reported no net rotation of the Eocene Bremerton volcanic rocks, east of the Olympic Mountains. All paleomagnetic data south and southeast of the Olympic Mountains, including the Blakely Formation, the Humptulips Formation, and many earlier results on Eocene rocks south of the Olympics [67][68][69][70][71][72][73] show a consistent clockwise rotation.…”

Section: Tectonic Rotationmentioning

confidence: 99%

Magnetostratigraphy and Tectonic Rotation of the Eocene-Oligocene Makah and Hoko River Formations, Northwest Washington, USA

Prothero

Draus

Burns

2009

International Journal of Geophysics

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The Eocene-Oligocene Makah Formation and subjacent middle Eocene Hoko River Formation of the northwestern Olympic Peninsula, Washington, yield mollusks, crustaceans, foraminifera, and early neocete whales; their age has never been precisely established. We sampled several sections; most samples showed a stable single-component remanence held largely in magnetite and passed a Class I reversal test. The upper Refugian (late Eocene) and lower Zemorrian (early Oligocene) rocks at Baada Point correlate with Chron C13r (33.7-34.7 Ma) and Chron C12r (30-33 Ma). The Ozette Highway section of the Makah Formation spanned the early Refugian to late Refugian, with a sequence that correlates with Chrons C15r-C13r (33.7-35.3 Ma), and a long reversed early Zemorrian section that correlates with Chron C12r (30-33 Ma). The type section of the Hoko River Formation correlates with Chron C18r (40.0-41.2 Ma). The area sampled shows about 45• of post-Oligocene counterclockwise tectonic rotation, consistent with results obtained from the Eocene-Oligocene rocks in the region.

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Paleomagnetism of small basalt exposures in the West Puget Sound Area, Washington, and Speculations on the accretionary origin of the Olympic Mountains

Cited by 33 publications

References 17 publications

Paleogeographic evolution of the United States Pacific Northwest during Paleogene time

Paleogeographic evolution of the United States Pacific Northwest during Paleogene time

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

Magnetostratigraphy and Tectonic Rotation of the Eocene-Oligocene Makah and Hoko River Formations, Northwest Washington, USA

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