Relative paleointensity of the geomagnetic field during the Brunhes Chron

Yamazaki, T.; Ioka, Noboru; Eguchi, N.

doi:10.1016/0012-821x(95)00189-j

Cited by 37 publications

(36 citation statements)

References 32 publications

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“…The Manihiki Plateau lies in the South Pacific Subtropical Gyre, and core KR9912‐PC5 is composed of pale yellowish white foraminiferal ooze. The paleomagnetism of these cores was reported by Yamazaki et al [1995] (NGC36), Yamazaki [1999] (NGC65), Yamazaki [2002] (NGC36 and NGC88), and Yamazaki and Oda [2005] (KR9912‐PC5).…”

Section: Sediment Cores and Age Controlmentioning

confidence: 87%

Environmental magnetism of Pleistocene sediments in the North Pacific and Ontong‐Java Plateau: Temporal variations of detrital and biogenic components

Yamazaki

2009

Geochem Geophys Geosyst

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109

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[1] An environmental magnetic study was conducted to investigate temporal variations of the sources of magnetic minerals in the Pacific Ocean using sediment cores of Pleistocene age. The proportion of interacting (I) to noninteracting (N-I) single-domain components was estimated from first-order reversal curve diagrams, and the proportion of middle-(M) to low-(L) coercivity components was determined from decomposition of isothermal remanent magnetization (IRM) acquisition curves. The I and M components are interpreted to be carried by terrigenous maghemite, while the N-I and L components represent biogenic magnetite. An inverse correlation between the ratio of anhysteretic remanent magnetization susceptibility (c ARM ) to saturation IRM (SIRM) and the I/N-I ratio was confirmed for sediments across wide expanses in the Pacific Ocean. This implies that c ARM /SIRM can be used to estimate the relative abundances of biogenic and terrigenous components in sediments. In the North Pacific, the relative abundance of the I and M components increases in glacial periods. Variations of c ARM /SIRM and S ratio (S À0.1T ) resemble each other and decrease in the same time intervals. These variations reflect increases of terrigenous input in glacial periods as eolian dust. On the Ontong-Java Plateau in the western equatorial Pacific, on the other hand, minima in c ARM /SIRM and S À0.1T occur at glacial-to-interglacial transitions, and the relative abundance of the I and M components increases in these periods. Terrigenous material in this region is considered to be transported mainly from the New Guinea and Solomon Islands by the Equatorial Undercurrent. The higher proportion of the terrigenous component at glacial-to-interglacial transitions is coeval with carbonate preservation maxima reported from the Ontong-Java Plateau, suggesting a linkage between the two.

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Section: Sediment Cores and Age Controlmentioning

confidence: 87%

Environmental magnetism of Pleistocene sediments in the North Pacific and Ontong‐Java Plateau: Temporal variations of detrital and biogenic components

Yamazaki

2009

Geochem Geophys Geosyst

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109

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“…The asymmetric sawtooth pattern observed in deep sea sediments (Ninkovich et al 1966;Kobayashi et al 1971;Opdyke et al 1973;Valet and Meynadier 1993;Meynadier et al 1992;Yamazaki et al 1995;Verosub et al 1996) consists of an apparent rapid rise in relative paleointensity immediately after a geomagnetic field reversal, followed by a slow decay until the next reversal (Fig. 3).…”

Section: The Asymmetric Sawtoothmentioning

confidence: 96%

Cosmogenic Be-10 and the Solid Earth: Studies in Geomagnetism, Subduction Zone Processes, and Active Tectonics

Morris¹,

Gosse

Brachfeld

et al. 2002

Reviews in Mineralogy and Geochemistry

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“…Optimum demagnetization is tuned to eliminating viscous overprints without rendering the signal unmeasurably weak. In recent studies, a wide variety of fields and temperatures were used: 10 mT [ Peck et al , 1996; Yamazaki et al , 1995], 15 mT [ Verosub et al , 1996; Yamazaki and Ioka , 1994], 17.5 mT [ Tauxe and Hartl , 1997], 20 mT [ Clement and Kent , 1991; Meynadier et al , 1994, 1995; Tric et al , 1992; Valet et al , 1994; Yamazaki and Oda , 2001, 2002], 25 mT [ Roberts et al , 1997], 30 mT [ Haag , 2000; Pan et al , 2001], 40 mT, [ Glen et al , 1999], averages of more than two steps [ Brachfeld and Banerjee , 2000; Channell et al , 2002; Dinares‐Turell et al , 2002; Guyodo et al , 2001; Meynadier et al , 1992], and thermal demagnetization to 420°C [ Laj et al , 1996]. …”

Section: Implications For Paleomagnetism and Paleointensity Determinamentioning

confidence: 99%

Decay‐rate dependence of anhysteretic remanence: Fundamental origin and paleomagnetic applications

Dunlop

2003

J. Geophys. Res.

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[1] We have measured the intensity of anhysteretic remanent magnetization (ARM) as a function of alternating field (AF) decay rate. For synthetic and natural single-domain (SD) and pseudo-single-domain (PSD) magnetites, ARM intensity increases as decay rate decreases. Multidomain (MD) magnetites have the opposite response, ARM increasing as the decay rate increases. These are identical to the SD/PSD and MD dependences of thermoremanent magnetization on cooling rate. For all grain sizes and domain structures, ARM intensity increases as the AF decay rate used to achieve an initial demagnetized state decreases. Decay-rate differences in ARM intensity are a property of low-and medium-coercivity grains, as shown by annealing and by stepwise AF demagnetizing samples. We interpret the SD results to mean that increased AF exposure time permits a closer approach to equilibrium magnetization. An approximate thermal activation theory based on Néel [1949] and an exact theory by Egli and Lowrie [2002] predict 6-11% increases in ARM for an order of magnitude decrease in decay rate, in reasonable accord with the observed 12% increase for 0.065 mm SD grains. For MD grains, we hypothesize that increased exposure time (slower decay) permits more efficient self-demagnetization, reducing ARM. Low-coercivity grains experience the largest self-demagnetizing fields and therefore have the largest decay-rate response. Initial-state decay-rate response is attributed to longer exposure times leaving domain walls more strongly pinned in deeper potential wells (the net self-demagnetizing field is zero in the demagnetized state). Acquisition decay-rate, annealing, and initial-state responses of PSD grains are a blend of SD and MD responses. Because ARM is the most frequently used normalizer in relative paleointensity determination, it is important either to use a standard decay rate or else to remove the decay-rate dependence by demagnetizing the ARM to $30% of its initial value (ARM 0.3 ). A standard demagnetization level for the normalizing ARM is particularly important when comparing paleointensity records from different laboratories.

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Relative paleointensity of the geomagnetic field during the Brunhes Chron

Cited by 37 publications

References 32 publications

Environmental magnetism of Pleistocene sediments in the North Pacific and Ontong‐Java Plateau: Temporal variations of detrital and biogenic components

Environmental magnetism of Pleistocene sediments in the North Pacific and Ontong‐Java Plateau: Temporal variations of detrital and biogenic components

Cosmogenic Be-10 and the Solid Earth: Studies in Geomagnetism, Subduction Zone Processes, and Active Tectonics

Decay‐rate dependence of anhysteretic remanence: Fundamental origin and paleomagnetic applications

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