Birth of an intraoceanic spreading center

Barckhausen, Udo; Ranero, César R.; Cande, S. C.; Engels, M.; Weinrebe, Wilhelm

doi:10.1130/g25056a.1

Cited by 51 publications

(36 citation statements)

References 9 publications

(17 reference statements)

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“…This is an example of mature crust formed at fast-spreading rates away from any plate reorganizations where no dipping events have been imaged. Likewise, dipping lower crustal structures are not observed at studied active mid-ocean ridges, up to 85 km away from the EPR in some places (Barth and Mutter, 1996), or in ophiolites.…”

Section: Normal Versus Anomalous Spreadingmentioning

confidence: 94%

“…Dipping events in the lower crust over a bright Moho in the Juan de Fuca plate only occur in an 8-my-old segment of the crust (Han et al, 2013) accreted when a plate reorganization took place (Wilson et al, 1984). Dipping events in the Cocos lower crust (Hallenborg et al, 2003) are observed in the 15-17 Ma crust formed at the East Pacific Rise (EPR) between the Pacific and Cocos Plates in the vicinity of the Cocos-Nazca-Pacific triple junction and Galapagos hotspot (e.g., Meschede et al, 1998;Barckhausen et al, 2008). The Cocos-Nazca spreading center has a complex history including several reorganizations and ridge jumps (e.g., at 19.5 and 14.5 Ma) towards the Galapagos hotspot system (∼150 km away).…”

Section: Normal Versus Anomalous Spreadingmentioning

confidence: 98%

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Origin of dipping structures in fast-spreading oceanic lower crust offshore Alaska imaged by multichannel seismic data

Bécel

Shillington

Nedimović

et al. 2015

Earth and Planetary Science Letters

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Multi-channel seismic (MCS) reflection profiles across the Pacific Plate south of the Alaska Peninsula reveal the internal structure of mature oceanic crust (48)(49)(50)(51)(52)(53)(54)(55)(56) formed at fast to intermediate spreading rates during and after a major plate re-organization. Oceanic crust formed at fast spreading rates (half spreading rate ∼74 mm/yr) has smoother basement topography, thinner sediment cover with less faulting, and an igneous section that is at least 1 km thicker than crust formed at intermediate spreading rates (half spreading rate ∼28-34 mm/yr). MCS data across fast-spreading oceanic crust formed during plate re-organization contain abundant bright reflections, mostly confined to the lower crust above a highly reflective Moho transition zone, which has a reflection coefficient (RC) of ∼0.1. The lower crustal events dip predominantly toward the paleo-ridge axis at ∼10-30 • . Reflections are also imaged in the uppermost mantle, which primarily dip away from the ridge at ∼10-25 • , the opposite direction to those observed in the lower crust. Dipping events in both the lower crust and upper mantle are absent on profiles acquired across the oceanic crust formed at intermediate spreading rates emplaced after plate re-organization, where a Moho reflection is weak or absent. Our preferred interpretation is that the imaged lower crustal dipping reflections within the fast spread crust arise from shear zones that form near the spreading center in the region characterized by interstitial melt. The abundance and reflection amplitude strength of these events (RC ∼ 0.15) can be explained by a combination of solidified melt that was segregated within the shear structures, mylonitization of the shear zones, and crystal alignment, all of which can result in anisotropy and constructive signal interference. Formation of shear zones with this geometry requires differential motion between the crust and upper mantle, where the upper mantle moves away from the ridge faster than the crust. Active asthenospheric upwelling is one possible explanation for these conditions. The other possible interpretation is that lower crustal reflections are caused by magmatic (mafic/ultramafic) layering associated with accretion from a central mid-crustal magma chamber. Considering that the lower crustal dipping events have only been imaged in regions that have experienced plate re-organizations associated with ridge jumps or rift propagation, we speculate that locally enhanced mantle flow associated with these settings may lead to differential motion between the crust and the uppermost mantle, and therefore to shearing in the ductile lower crust or, alternatively, that plate reorganization could produce magmatic pulses which may lead to mafic/ultramafic banding.Published by Elsevier B.V.

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Section: Normal Versus Anomalous Spreadingmentioning

confidence: 94%

Section: Normal Versus Anomalous Spreadingmentioning

confidence: 98%

Origin of dipping structures in fast-spreading oceanic lower crust offshore Alaska imaged by multichannel seismic data

Bécel

Shillington

Nedimović

et al. 2015

Earth and Planetary Science Letters

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“…11a). Since Miocene fission of the Farallon plate into the Cocos and Nazca plates (Barckhausen et al, 2008), there was a fourth: the Cocos-Caribbean-Nazca triple junction (D), which is a stable ridge-trench-trench triple junction subducting Cocos and Nazca lithosphere in the Central American trench (Fig. 11d).…”

Section: Cretaceous and Younger Plate Boundary Configurations And Trimentioning

confidence: 98%

“…The western boundary of the Caribbean plate is the Central America Trench, accommodating eastward subduction of the Cocos plate and before the Miocene the Farallon plate (Barckhausen et al, 2008), below the Caribbean plate. The Central American land bridge can be divided into several tectonic blocks, from north to south including: the Chortis Block, the Southern Chortis terrane, the Siuna block and the Panama-Chocó block (Fig.…”

Section: Central Americamentioning

confidence: 99%

Kinematic reconstruction of the Caribbean region since the Early Jurassic

Boschman

Hinsbergen

Torsvik

et al. 2014

Earth-Science Reviews

255

300

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“…These plate pairs are in order of decreasing spreading rate: Pacific-Nazca, Pacific-Juan de Fuca, Australia-Antarctic, and Pacific-Antarctic. Data for the Pacific-Nazca pair are limited to the northern part of the system, which is well surveyed from studies of the separation of the Cocos plate from the northern Nazca plate during chron C6Bn (Lonsdale, 2005;Barckhausen et al, 2008). Pacific-Juan de Fuca data are from immediately north of the Mendocino fracture zone.…”

Section: Reversal Ages Based On Plate-pair Spreading Ratesmentioning

confidence: 99%

Astronomical tunings of the Oligocene–Miocene transition from Pacific Ocean Site U1334 and implications for the carbon cycle

et al. 2018

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Abstract. Astronomical tuning of sediment sequences requires both unambiguous cycle pattern recognition in climate proxy records and astronomical solutions, as well as independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the Oligocene-Miocene transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning has on astronomically calibrated ages and the geologic timescale. These alternative age models (roughly from ∼ 22 to ∼ 24 Ma) are based on different tunings between proxy records and eccentricity: the first age model is based on an aligning CaCO 3 weight (wt%) to Earth's orbital eccentricity, and the second age model is based on a direct age calibration of benthic foraminiferal stable carbon isotope ratios (δ 13 C) to eccentricity. To independently test which tuned age model and associated tuning assumptions are in best agreement with independent ages based on tectonic plate-pair spreading rates, we assign the tuned ages to magnetostratigraphic reversals identified in deep-marine magnetic anomaly profiles. Subsequently, we compute tectonic plate-pair spreading rates based on the tuned ages. The resultant alternative spreading-rate histories indicate that the CaCO 3 tuned age model is most consistent with a conservative assumption of constant, or linearly changing, spreading rates. The CaCO 3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n-C7n.1r, which are not based on astronomical tuning in the latest iteration of the geologic timescale. Furthermore, it provides independent evidence that the relatively large (several 10 000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity constitute a real feature of the OligoceneMiocene climate system and carbon cycle. The age constraints from Site U1334 thus indicate that the delayed responses of the Oligocene-Miocene climate-cryosphere system and (marine) carbon cycle resulted from highly nonlinear feedbacks to astronomical forcing.

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Birth of an intraoceanic spreading center

Cited by 51 publications

References 9 publications

Origin of dipping structures in fast-spreading oceanic lower crust offshore Alaska imaged by multichannel seismic data

Origin of dipping structures in fast-spreading oceanic lower crust offshore Alaska imaged by multichannel seismic data

Kinematic reconstruction of the Caribbean region since the Early Jurassic

Astronomical tunings of the Oligocene–Miocene transition from Pacific Ocean Site U1334 and implications for the carbon cycle

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