Magnetostratigraphy in three Arctic Ocean sediment cores; arguments for geomagnetic excursions within oxygen-isotope stage 2–3

Løvlie, Reidar; Markussen, Berit; Sejrup, Hans Petter; Thiede, Jörn

doi:10.1016/0031-9201(86)90084-1

Cited by 62 publications

(20 citation statements)

References 12 publications

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“…It is significant that the direction of the horizontal component of magnetization is aligned along the axis of "push" of the discrete sample boxes into the sediment core. This phenomenon was originally noticed during sampling of soft clays by Gravenor et al (1984) and subsequently has been documented from a wide range of soft marine sediments taken with gravity, piston, and Kasten corers (L0vlie et al, 1986;Hailwood et al, 1989) still uncertain, but it is likely to involve a mechanical realignment of the magnetic grains caused by the shearing action during insertion of the sample box. Measurement of magnetic susceptibility anisotropy (magnetic fabric) of marine sediment samples showing this effect (Hailwood et al, 1989) indicates that the long axes of the magnetic grains are preferentially aligned along the push axis and that this property is not restricted to the surface layers of the sample, but instead penetrates deep into its interior.…”

Section: Magnetic Declination and Sampling Disturbancesmentioning

confidence: 88%

Magnetostratigraphy of Sites 703 and 704, Meteor Rise, Southeastern South Atlantic

Hailwood¹,

Clement²

1991

Proceedings of the Ocean Drilling Program

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ODP Sites 703 and 704 were drilled near the crest of the Meteor Rise in the southeastern part of the South Atlantic in order to explore the role of this aseismic rise as a barrier to the flow of deep water between the Antarctic and South Atlantic during the early evolution of the South Atlantic and to investigate the subsequent subsidence and paleoceanographic evolution of this area.A combination of shipboard whole-core paleomagnetic determinations on all archive core halves and post-cruise paleomagnetic analyses of some 440 discrete samples from the two sites has allowed definition of the sequence of geomagnetic polarity reversals that occurred during deposition of much of this sedimentary sequence. The magnetostratigraphic record for Sift 703 extends from the middle Eocene to the early Miocene and that for Site 704 from the early Miocene to the Pleistocene. The correlation of this record to the standard geomagnetic polarity time scale of Berggren et al. (1985) is generally good for the Oligocene and late Miocene to Pleistocene, but is poorer for the early and middle Miocene.The combined magnetostratigraphic record for these two sites will facilitate the development and chronometric calibration of refined high-latitude biostratigraphic zonations. Furthermore, it provides an important basis for defining the periodicity of the late Neogene stable isotope and carbonate fluctuations observed in these cores and relating these changes to the paleoclimatic and paleoceanographic driving forces.

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Section: Magnetic Declination and Sampling Disturbancesmentioning

confidence: 88%

Magnetostratigraphy of Sites 703 and 704, Meteor Rise, Southeastern South Atlantic

Hailwood¹,

Clement²

1991

Proceedings of the Ocean Drilling Program

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“…Note that the low‐coercivity and the low unblocking temperature part on the spectra may be susceptible to VRM. Titanomaghemite is known to have a propensity for acquisition of VRM [e.g., Özdemir and Banerjee , 1981], and Arctic sediments have been noted for their ability to acquire VRM that often resists moderate peak AF fields, up to >20 mT [e.g., Løvlie et al , 1986; Witte and Kent , 1988]. The low‐coercivity (generally <20 mT) and low unblocking temperature (<175°C) component with positive inclinations (Figure 3) may be drilling related and/or a VRM, or possibly a detrital remanent magnetization (DRM) carried by original (titano)magnetite with larger grain sizes (lower coercivities), or a mixture of remanence types.…”

Section: Discussionmentioning

confidence: 99%

Origin of apparent magnetic excursions in deep‐sea sediments from Mendeleev‐Alpha Ridge, Arctic Ocean

Xuan

Channell

2010

Geochem Geophys Geosyst

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Arctic deep‐sea sediments often record intervals of negative inclination of natural remanence that are tens of centimeters thick, implying magnetic excursions with durations of tens of thousand years that far exceed excursion durations estimated elsewhere, and the lack of tight age control usually provides excessive freedom in the labeling of Arctic excursions. Fortuitous variations in sedimentation rate have been invoked to explain the “amplified” excursions. Alternating field demagnetization of natural remanent magnetization (NRM) of sediment cores 08JPC, 10JPC, 11JPC, and 13JPC recovered by the Healy Oden Trans‐Arctic Expedition in August 2005 (HOTRAX05) to the Mendeleev‐Alpha Ridge yields apparent magnetic “excursions” in sediments deposited in the Brunhes Chron. Thermal demagnetization of the NRM, however, implies multiple magnetization components with negative inclination components usually “unblocked” below ∼350°C. Analysis of isothermal remanent magnetization acquisition curves from magnetic extracts indicates two magnetic coercivity components superimposed on one another. Magnetic experiments conducted under high and low temperatures show features that are characteristic for (titano)magnetite and titanomaghemite. Presence of the two magnetic phases is further confirmed by elemental mapping on a scanning electron microscope equipped for X‐ray energy dispersive spectroscopy (EDS) and by high‐resolution X‐ray diffraction (XRD). It is unlikely that anomalously thick intervals of negative inclination in these Brunhes‐aged sediments are caused by unusual behavior of the magnetic field in the Arctic area. We therefore attribute low and negative NRM inclinations in these cores to partially self‐reversed chemical remanent magnetizations, apparently carried by titanomaghemite and acquired during the oxidation of detrital (titano)magnetite grains. The high Ti contents and high oxidation states indicated by EDS and XRD data provide the conditions required for partial self‐reversal by ionic reordering during diagenetic maghemitization, and this process appears to have affected all HOTRAX05 cores collected from the Mendeleev‐Alpha Ridge.

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“…The mm ka − 1 scale sedimentation rates of Clark et al (1980) have been questioned as they were solely based on the identification of the Brunhes/Matuyama paleomagnetic inclination reversal (Backman et al, 2004). Several more recent studies have shown that the paleomagnetic inclination change assumed to be the Brunhes/Matuyama in the central Arctic Ocean stratigraphy likely represents a younger excursion event (Løvlie et al, 1986;Bleil and Gard, 1989;Jakobsson et al, 2001;Nowaczyk et al, 2001;Nowaczyk et al, 2003;Spielhagen et al, 2004).…”

Section: Comparison Of 10 Be Fluxes Across the Arctic Oceanmentioning

confidence: 96%

Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores

Sellén

Kubik

2009

Global and Planetary Change

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Magnetostratigraphy in three Arctic Ocean sediment cores; arguments for geomagnetic excursions within oxygen-isotope stage 2–3

Cited by 62 publications

References 12 publications

Magnetostratigraphy of Sites 703 and 704, Meteor Rise, Southeastern South Atlantic

Magnetostratigraphy of Sites 703 and 704, Meteor Rise, Southeastern South Atlantic

Origin of apparent magnetic excursions in deep‐sea sediments from Mendeleev‐Alpha Ridge, Arctic Ocean

Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores

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