Role of magnetic interaction in sediments.

Hamano, Yozo

doi:10.5636/jgg.35.173

Cited by 5 publications

(3 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These include (1) wetting a powder and allowing it to stand in the presence of a field [e.g., Irving and Major, 1964], (2) deposition of a slurry in zero field and allowing it to stand in a field [Clegg et al, 1954;Barton et al, 1980;Tauxe and Kent, 1984;Khramov, 1968], (3) deposition of a slurry in a field, changing the field conditions, and then monitoring changes in remanence [Johnson et al, 1948;LCvlie, 1974LCvlie, , 1976Graham, 1974;Barton and McE1hinny, 1979;Tucker, 1979Tucker, , 1980aVerosub et al, 1979;Payne and Verosub, 1982], and (4) monitoring of remanence while the sediment undergoes compaction [e.g., Blow and Hamilton, 1978;Hamano, 1980; Otooeuji and $asajima, 1981; Anson and Kodama, 1987; Deamer and Kodama, 1990]. The magnetization acquired in this region has also been considered theoretically [Tucker, 1980a;Hamano, 1980Hamano, , 1983Denham and Chave, 1982;Hyodo, 1984]. I will call attention to the aspects of these experiments important for paleointensity studies.…”

Section: Initial Consolidation Without Disturbancementioning

confidence: 99%

See 1 more Smart Citation

Sedimentary records of relative paleointensity of the geomagnetic field: Theory and practice

Tauxe¹

1993

Reviews of Geophysics

557

450

View full text Add to dashboard Cite

the record prior to about 300 ka; thus they are probably not an inherent feature in the geomagnetic field, and the correspondence of the period of oscillation to that of obliquity is probably coincidence. 1.clides as •4C and •øBe, and the radiocarbon timescale is built upon the assumption that the rate of production is constant. Detailed calibration of the radiocarbon dates using tree rings and varved sediments of known age resulted in the discovery of rather large discrepancies [e.g., Stuiver et al., 1986], and these deviations can be reasonably well modeled as resulting from changes in Earth's magnetic field (see Figure 1). This calibration is available only for the last 10 ka or so, and direct calibration prior to that time is based on a very few spot calibration points comparing radiocarbon ages with those derived from thorium decay [see Bard Observatory measurements effects in order to obtain the contribution of the magnetic field. Under the ideal conditions shown in Figure 3, DRM normalized by magnetic activity yields estimates of the paleofield intensity B* that is linearly related to the ancient magnetic field. Of course, the slope relating B* and B may never be known. The experimental and theoretical basis for estimating [ma] is relatively undeveloped. I will highlight results from landmark papers that serve as the foundations for all sedimentary paleointensity studies. These papers provide hope that there may be sediments that retain a recoverable record of paleofield intensities if properly normalized. I will describe the conditions under which such records are created and the available techniques for analyzing them. Finally, I have collected some representative records of relative paleointensity from sediments and will draw a few general conclusions from them. The paleomagnetic literature suffers from confusion about units and terms and is therefore at times difficult to read and to interpret. I have redrafted all figures in order to standardize the units according to the Syst•rne International (SI). Table 1 lists some useful conversions among the various units in the original literature. I will describe all magnetizations in terms of moment rn or magnetization M. Magnetic fields are denoted either as H or as B. B is usually referred to as the magnetic induction, but often in the paleomagnetic context B is also called the magnetic field; the two will •20 be distinguished by using the appropriate units and associated letter. I note in passing that the change from using cgs units to SI units in the early 1980s has led to an enormous amount of confusion because many measurements are still made in cgs units and conversion is ubiquitous and frequently done incorrectly. Nearly every table in the paleomagnetic literature listing unit conversion contains confusing, misleading, or erroneous statements [see Payne, 1981; King et al., 1983;Butler, 1992]. I will adhere to the usage in Table 1 throughout the paper. Magnetic remanence is the magnetization measured in the absence of an applied field. I will call, by...

show abstract

Section: Initial Consolidation Without Disturbancementioning

confidence: 99%

“…Experimental work on the blocking of magnetic remanence gave rise to several theoretical papers [Denham and Chave, 1982;Hamano, 1983;Hyodo, 1984]. Denham and Chave [1982] started with (1) and solved it using the small-angle approximation where sin 0 -• 0 and grain radius is r:…”

Section: Figure 10bmentioning

confidence: 99%

Sedimentary records of relative paleointensity of the geomagnetic field: Theory and practice

Tauxe¹

1993

Reviews of Geophysics

557

450

View full text Add to dashboard Cite

show abstract

“…If the intensity of the magnetization of the sediments exaggerates the variations of the geomagnetic field, the present variations of the magnetic intensity may be explained. Hamano (1983) demonstrated that magnetic interaction between magnetic particles affects the intensity of the remanence, and the effect is larger for smaller particles (higher spontaneous magnetization) and for lower concentrations of the magnetic minerals. This effect of the magnetic interaction exerts some non-linear influence on the relation between the ambient geomagnetic field intensity and the intensity of magnetization in sediments.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Intensity Variations in Sediment Cores from Leg 128

Hamano¹,

Krumsiek²

1992

Proceedings of the Ocean Drilling Program

View full text Add to dashboard Cite

Variations of the intensity of magnetization in the sediment cores from Sites 798 and 799 were examined. Closely correlated variations in the magnetic intensity enabled estimation of the relative change of the sedimentation rate between the two sites. A high sedimentation rate of more than 30 cm/1,000 yr was inferred for about 550,000 yr ago at Site 799. The sedimentation rate was used to compare the distribution of volcanic ash layers at two sites.

show abstract

Magnetic anisotropy, scanning electron microscopy, and X ray pole figure goniometry study of inclination shallowing in a compacting clay‐rich sediment

Sun¹,

Kodama²

1992

J. Geophys. Res.

View full text Add to dashboard Cite

Anisotropy of anhysteretic remanence (AAR), scanning electron microscopy (SEM), and X ray pole figure goniometry studies of clay‐rich sediments were conducted to delineate the interactions between magnetite and clay particles which cause inclination shallowing during compaction. These studies used synthetic sediments composed of kaolinite or illite and two grain sizes of magnetite, 0.45 μm and 2–3 μm. Natural marine sediments which contained 40–50% clay were also used. The sediments were compacted by pressures as high as 0.157 MPa. The sediments' porosity decrease suggests that the compaction experiments model burial depths up to 400–500 m. The main result of this study is that inclination shallowing and void ratio versus pressure curves show two points where behavior changes. A rapid decrease in inclination and void ratio occurs up to a pressure of 0.02 MPa. This is accompanied by a magnetic intensity decrease of 20–30%. Compaction at pressures between 0.02 MPa and 0.05 MPa causes a further decrease in these parameters at moderate rates, while compaction at pressures above 0.05 MPa causes very little change. Percent magnetic anisotropy and X ray pole figure intensity ratio versus pressure curves show only one point where behavior changes at 0.05 MPa with a rapid increase at lower pressures and little change at higher pressures. A model to explain this behavior, based on the SEM observations as well as the magnetic anisotropy, pole figure, and inclination data, suggests that compaction up to 0.02 MPa causes a decrease in pore volume with little reorientation of clay particles. Some magnetic particles are firmly attached to clay particles, whereas other loosely attached particles are either randomized or subvertical ones are preferentially disturbed causing inclination shallowing and an intensity decrease. At pressures between 0.02 MPa and 0.05 MPa, magnetite particles have become firmly attached to clay particles and start to follow the reorientation of clay particles as the clay fabric develops. At 0.05 MPa there is a major change in the clay microstructure with a horizontal fabric becoming evident. Compaction at higher pressures causes little further volume loss and clay particle reorientation and hence little additional inclination shallowing. The randomization/disturbance process suggested by this model causes slightly more than half of the inclination shallowing observed in the samples studied, whereas magnetite‐clay attachment causes the remainder of the inclination decrease.

show abstract

Role of magnetic interaction in sediments.

Cited by 5 publications

References 19 publications

Sedimentary records of relative paleointensity of the geomagnetic field: Theory and practice

Sedimentary records of relative paleointensity of the geomagnetic field: Theory and practice

Magnetic Intensity Variations in Sediment Cores from Leg 128

Magnetic anisotropy, scanning electron microscopy, and X ray pole figure goniometry study of inclination shallowing in a compacting clay‐rich sediment

Contact Info

Product

Resources

About