Mesozoic magnetic anomaly lineations and seafloor spreading history of the northwestern Pacific

Nakanishi, Masao; Tamaki, Kensaku; Kobayashi, Kazuo

doi:10.1029/jb094ib11p15437

Cited by 195 publications

(240 citation statements)

References 63 publications

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“…The earliest well-documented reorganization occurs in the middle Tithonian, at about magnetic anomaly M21 to M20. In the vicinity of the small Pacific Plate, the middle Tithonian event resulted in an eastward jump of the Japanese-Hawaiian ridge-junction and onset of Shatsky Rise plateau-building , Nakanishi et al, 1989. Paleomagnetic data indicates that the Pacific Plate also underwent a middle Tithonian reversal in direction of paleolatitude drift from northward to southward ( Fig.…”

Section: Tectonic Disruptions and Reorganizationsmentioning

confidence: 98%

“…Shatksy Rise may represent a hotspot outpouring in association with the triple junction (Sharman and Risch, 1988;, and references therein; Nakanishi et al, 1989). The trend of Shatksy Rise is not linear, which may be an artifact of the triple junction moving back and forth across a hotspot (E. L. Winterer, pers, comm., 1991).…”

Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

“…These events are recognized through a widespread reorientation of spreading directions and the onset or termination of volcanic activity. A change in relative spreading rates of the Japanese or the Hawaiian ridge or both may have occurred at magnetic polarity chron M25 (Nakanishi et al, 1989). The earliest well-documented reorganization occurs in the middle Tithonian, at about magnetic anomaly M21 to M20.…”

Section: Tectonic Disruptions and Reorganizationsmentioning

confidence: 99%

“…It would be expected that pelagic sediments deposited during such tectonic episodes may have elevated levels of FeMn-oxide and of Fe-smectite clays. An episode of clay-enrichment in the middle Tithonian at Site 801 may be a by-product of the reorganization of Pacific spreading centers between magnetic polarity chrons M20 and M21 Handschumacher et al, 1988;Nakanishi et al, 1989) and reversal of plate motion (Fig. 3).…”

Section: Iron and Manganesementioning

confidence: 99%

“…3). Another set of widespread spreading center disruptions occurred in the Pacific during the late Valanginian between magnetic polarity chrons Mil and M10 Nakanishi et al, 1989). This episode and possible associated regional volcanic activity may have contributed to the deposition of clay-rich radiolarite at Site 196 and may be exhibited at Site 801 as a hardground overlain by distal volcanic turbidites.…”

Section: Iron and Manganesementioning

confidence: 99%

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Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Ogg¹,

Stattegger²,

Behl³

1992

Proceedings of the Ocean Drilling Program, 129 Scientific Results

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Sedimentation in the central Pacific during the Jurassic and Early Cretaceous was dominated by abundant biogenic silica. A synthesis of the stratigraphy, lithology, petrology, and geochemistry of the radiolarites in Sites 801 and 800 documents the sedimentation processes and trends in the equatorial central Pacific from the Middle Jurassic through the Early Cretaceous. Paleolatitude and paleodepth reconstructions enable comparisons with previous DSDP sites and identification of the general patterns of sedimentation over a wide region of the Pacific.Clayey radiolarites dominated sedimentation on Pacific oceanic crust within tropical paleolatitudes from at least the latest Bathonian through Tithonian. Radiolarian productivity rose to a peak within 5° of the paleoequator, where accumulation rates of biogenic silica exceeded 1000 g/cm 2 /m.y. Wavy-bedded radiolarian cherts developed in the upper Tithonian at Site 801 coinciding with the proximity of this site to the paleoequator. Ribbon-bedding of some radiolarian cherts exposed on Pacific margins may have formed from silicification of radiolarite deposited near the equatorial high-productivity zone where radiolarian/clay ratios were high. Silicification processes in sediments extensively mixed by bioturbation or enriched in clay or carbonate generally resulted in discontinuous bands or nodules of porcellanite or chert, e.g., a "knobby" radiolarite. Ribbon-bedded cherts require primary alternations of radiolarian-rich and clay-rich layers as an initial structural template, coupled with abundant biogenic silica in both layers. During diagenesis, migration of silica from clay-rich layers leaves radiolarian "ghosts" or voids, and the precipitation in adjacent radiolarite layers results in silicification of the inter-radiolarian matrix and infilling of radiolarian tests. Alternations of claystone and clay-rich radiolarian grainstone were deposited during the Callovian at Site 801 and during the Berriasian-Valanginian at Site 800, but did not silicify to form bedded chert.Carbonate was not preserved on the Pacific oceanic floor or spreading ridges during the Jurassic, perhaps due to an elevated level of dissolved carbon dioxide. During the Berriasian through Hauterivian, the carbonate compensation depth (CCD) descended to approximately 3500 m, permitting the accumulation of siliceous limestones at near-ridge sites. Carbonate accumulation rates exceeded 1500 g/cm 2 /m.y. at sites above the CCD, yet there is no evidence of an equatorial carbonate bulge during the Early Cretaceous. In the Barremian and Aptian, the CCD rose, coincident with the onset of mid-plate volcanic activity.Abundance of Fe and Mn and the associated formation of authigenic Fe-smectite clays was a function of proximity to the spreading ridges, with secondary enrichments occurring during episodes of spreading-center reorganizations. Callovian radiolarite at Site 801 is anomalously depleted in Mn, which resulted either from inhibited precipitation of Mn-oxides by lower pH of interstitial waters in...

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Section: Tectonic Disruptions and Reorganizationsmentioning

confidence: 98%

Section: Ridge Configuration and Oceanic Plateausmentioning

confidence: 99%

Section: Tectonic Disruptions and Reorganizationsmentioning

confidence: 99%

Section: Iron and Manganesementioning

confidence: 99%

Section: Iron and Manganesementioning

confidence: 99%

See 3 more Smart Citations

Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Ogg¹,

Stattegger²,

Behl³

1992

Proceedings of the Ocean Drilling Program, 129 Scientific Results

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Relationship between the Cascadia fore-arc mantle wedge, nonvolcanic tremor, and the downdip limit of seismogenic rupture

McCrory

Hyndman

Blair

2014

Geochem. Geophys. Geosyst.

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Great earthquakes anticipated on the Cascadia subduction fault can potentially rupture beyond the geodetically and thermally inferred locked zone to the depths of episodic tremor and slip (ETS) or to the even deeper fore-arc mantle corner (FMC). To evaluate these extreme rupture limits, we map the FMC from southern Vancouver Island to central Oregon by combining published seismic velocity structures with a model of the Juan de Fuca plate. These data indicate that the FMC is somewhat shallower beneath Vancouver Island (36-38 km) and Oregon (35-40 km) and deeper beneath Washington (41-43 km). The updip edge of tremor follows the same general pattern, overlying a slightly shallower Juan de Fuca plate beneath Vancouver Island and Oregon (30 km) and a deeper plate beneath Washington (35 km). Similar to the Nankai subduction zone, the best constrained FMC depths correlate with the center of the tremor band suggesting that ETS is controlled by conditions near the FMC rather than directly by temperature or pressure. Unlike Nankai, a gap as wide as 70 km exists between the downdip limit of the inferred locked zone and the FMC. This gap also encompasses a 50 km wide gap between the inferred locked zones and the updip limit of tremor. The separation of these features offers a natural laboratory for determining the key controls on downdip rupture limits.

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Pn anisotropy in Mesozoic western Pacific lithosphere

et al. 2014

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Pn is the high-frequency, scattered P phase guided for great distances within the old oceanic lithosphere. Two arrays of ocean bottom seismometers were deployed on old (150-160 Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the Pacific Lithosphere Anisotropy and Thickness Experiment. We use Pn phases from 403 earthquakes during the 1 year of deployment to measure apparent velocities across the arrays. Each array was deployed on a separate limb of a magnetic bight, formed near a fast-spreading, ridge-ridge-ridge triple junction. Using high-frequency waves (5-10 Hz), we look at variations of Pn velocities as a function of azimuth. In the western array, we find Pn anisotropy with velocities ranging from~8.7 km/s in the back azimuth (θ) direction of 310°to~7.7 km/s at~350°. In the eastern array, the velocity ranges from~8.5 km/s in back azimuth direction of~210°to~7.7 km/s at 260°and~310°. We observe rapid velocity changes with azimuth in the both arrays requiring sinusoidal variations of roughly equal amplitude as a function of both 2θ and 4θ, which is not expected for the orthorhombic symmetry of olivine or orthopyroxene. The fastest directions on the two limbs are roughly orthogonal to each other suggesting the dominance of fossil anisotropy, but the fast directions of the 2θ components are skewed counterclockwise from the spreading directions. We speculate that the rapid azimuthal variations may be caused by vertical stratification with changing anisotropy with depth in the oceanic lithosphere.

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Mesozoic magnetic anomaly lineations and seafloor spreading history of the northwestern Pacific

Cited by 195 publications

References 63 publications

Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Jurassic through Early Cretaceous Sedimentation History of the Central Equatorial Pacific and of Sites 800 and 801

Relationship between the Cascadia fore-arc mantle wedge, nonvolcanic tremor, and the downdip limit of seismogenic rupture

Pn anisotropy in Mesozoic western Pacific lithosphere

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