Compaction-induced inclination shallowing of the post-depositional remanent magnetization in a synthetic sediment

Anson, G. L.; Kodama, Kenneth P.

doi:10.1111/j.1365-246x.1987.tb01651.x

Cited by 172 publications

(111 citation statements)

References 27 publications

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“…Similarly, inclinations of the Tertiary sediment samples in the earlier DSDP study appeared to be biased (13 of a total of 18 samples have a positive inclination). Inclination flattening during sediment compaction (Anson and Kodama, 1987;Arason and Levi, 1990;Deamer and Kodama, 1990;Levi and Baner-jee, 1990;Tarduno, 1990), a mechanism suggested as the explanation of other anomalous paleolatitude records from marine sediments, cannot explain this bias in the polarity distribution. An alternate explanation is that the alternating field (AF) demagnetization conducted in the two studies (to a maximum of 30 mT in the DSDP study, with characteristic inclinations determined at 10 mT, and to a maximum of 15 mT on board Leg 130) was unable to completely remove an overprint.…”

Section: Introductionmentioning

confidence: 87%

Magnetic Diagenesis, Organic Input, Interstitial Water Chemistry, and Paleomagnetic Record of the Carbonate Sequence on the Ontong Java Plateau

Musgrave¹,

Delaney²,

Stax³

et al. 1993

Proceedings of the Ocean Drilling Program, 130 Scientific Results

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Shipboard paleomagnetic studies on Ocean Drilling Program Leg 130 were plagued by a severe reduction in the remanence intensity, which affected sediments below a sharply defined onset at sub-bottom depths of 50 mbsf or less. This loss of intensity was accompanied by a reduction in magnetic stability and consequent loss of polarity and paleolatitude information. Viscous remanent magnetization and drilling-induced remanences contributed high-coercivity overprints, further obscuring the greatly diminished primary magnetization. The depth at which the reduction in intensity occurred correlates with the organic carbon content of the sediments, and a further relationship is present between intensity downhole and the level of sulfate reduction. This implies that loss of intensity is related to the microbial reduction of magnetite. Reduction of sulfate results in the generation of a magnetic iron sulfide, which appears to be the carrier of the high-coercivity overprints. Oxidation and drying of the sediment after sampling leads to partial destruction of this sulfide, and complete decomposition occurs at temperatures below 300°C. These features identify the magnetic sulfide as the metastable phase, greigite. Varying inputs of organic material in past times, presumably reflecting both latitude and climatic changes, resulted in varying degrees of reduction, which are now reflected in differences in magnetic intensity, degree of overprinting, and survival of primary magnetization. The highest reduction levels result in the almost total dissolution of magnetite, and the weak surviving remanence is dominated by greigite. At lower reduction states, multidomain magnetite persists together with greigite. Still-less-reducing conditions in turn cause the survival of fine-grained, single-domain magnetite, and then of hematite.An earlier paleomagnetic study of Ontong Java Plateau sediments from Deep Sea Drilling Project Leg 30 produced a paleolatitude curve that differed significantly from other records of Pacific paleolatitude. It is likely that the samples in this earlier study also carried high-coercivity overprints, which biased the results. Those samples from Leg 130 that appear to preserve a primary magnetization yielded paleolatitudes consistent with expected Pacific Plate motion.

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Section: Introductionmentioning

confidence: 87%

Magnetic Diagenesis, Organic Input, Interstitial Water Chemistry, and Paleomagnetic Record of the Carbonate Sequence on the Ontong Java Plateau

Musgrave¹,

Delaney²,

Stax³

et al. 1993

Proceedings of the Ocean Drilling Program, 130 Scientific Results

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“…Hence, there is probably a bias in inclination due to a secondary component. The most important cause of the inclination error, however, is most likely due to compaction and its magnitude is clearly related to the carbonate content [27], a result which is known from earlier studies [28,29].…”

Section: Nrm Componentsmentioning

confidence: 48%

The upper and lower Thvera sedimentary geomagnetic reversal records from southern Sicily

Hoof¹,

Langereis²

1992

Earth and Planetary Science Letters

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Detailed paleomagnetic records of the upper and lower Thvera polarity transitions have been determined from Pliocenc marine marls in southern Sicily. The dominant magnetic mineral is fine grained magnetite. The two transitions have VGP paths following a great circle passing South America and the west coast of North America. There are strong indications that the VGP paths result from smoothing of the non-antipodal stable directions before and after the transitions. The upper Thvera transitional record is preceded by two excursions and followed by a third one. The first excursion is a sedimentary artefact caused by post-depositional migration of magnetic minerals and the third one by is caused by weathering of the sediment. The upper Thvera transition from Sicily is compared with the record from Calabria, about 250 km away. The two records show similarities as well as differences: both transitions have identical VGP paths, but in Calabria the transition is recorded lower in the sediment, the first and third excursions have different characters and the second one is not present. Apparently the registration of transitions of the Earth's magnetic field in sediments is strongly influenced by smoothing and diagenetic processes after deposition.

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“…This is significantly different from the site geographical latitude of 12.49°N. Because the mean inclination is shallower than that corresponding to a geocentric axial dipole field (Io = 23.89°), a small but systematic inclination error of about 5 1/2° due to compaction may be present in this fine-grained globigerina ooze (ANSON and KODAMA, 1987;ARASON and LEVI, 1990a, b;GORDON, 1990;ABRAHAMSEN, 1992).…”

Section: Inclinationmentioning

confidence: 76%

Magnetic Variations and Possible Milankovitch Cycles in a Deep-Sea Core from the Central North Atlantic.

Abrahamsen

1993

J. geomagn. geoelec

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Magnetic measurements on 265 samples from an 8 m long deep-sea sediment gravity core, 450 km SW of Dakar, West Africa, are presented. The core is normally magnetized, thus being of Brunhes age (younger than 730 ka). Cyclic variations in the NRM intensity, the susceptibility, and especially 10 major and 20 minor cycles in the Q-ratio (Koenigsberger ratio) are discussed in relation to climatic variations. The possible effects of secondary magnetizations are not known, but because of the regular pattern in the Q-ratio, it is suggested that the periodicities in this ratio correspond to Milankovitch cycles with periods of 21 ka and 41 ka years, and therefore that the Q-ratio may be used as an easily-obtained time scale, and hence as a stratigraphical tool, in these kinds of deep-sea sediments.

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Compaction-induced inclination shallowing of the post-depositional remanent magnetization in a synthetic sediment

Cited by 172 publications

References 27 publications

Magnetic Diagenesis, Organic Input, Interstitial Water Chemistry, and Paleomagnetic Record of the Carbonate Sequence on the Ontong Java Plateau

Magnetic Diagenesis, Organic Input, Interstitial Water Chemistry, and Paleomagnetic Record of the Carbonate Sequence on the Ontong Java Plateau

The upper and lower Thvera sedimentary geomagnetic reversal records from southern Sicily

Magnetic Variations and Possible Milankovitch Cycles in a Deep-Sea Core from the Central North Atlantic.

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