Remanence anisotropy effect on the palaeointensity results obtained from various archaeological materials, excluding pottery

Kovacheva, Mary; Chauvin, Annick; Jordanova, Neli; Lanos, Philippe; Karloukovski, Vassil

doi:10.1186/bf03353179

Cited by 40 publications

(24 citation statements)

References 29 publications

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“…6; Supplementary material: Table S3; Kovacheva et al, 2009b). As expected, a low TRM anisotropy effect upon archaeointensities was found for the kilns, for which very low differences between uncorrected and TRM corrected intensities were generally obtained (Fig.…”

Section: French Kilns and Bricks Used For The Construction Of Historisupporting

confidence: 74%

Improving our knowledge of rapid geomagnetic field intensity changes observed in Europe between 200 and 1400 AD

Gómez‐Paccard

Chauvin

Lanos

et al. 2012

Earth and Planetary Science Letters

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a b s t r a c tAvailable archaeomagnetic data indicate that during the past 2500 yr there have been periods of rapid geomagnetic field intensity fluctuations interspersed with periods of almost constant field strength. Despite Europe being the most widely covered region in terms of archaeomagnetic data the occurrence and the behaviour of these rapid geomagnetic field intensity changes is under discussion and the challenge now is to precisely describe them. The aim of this study is to obtain an improved description of the sharp intensity change that took place in western Europe around 800 AD as well as to investigate if this peak is observed at the continental scale. For this purpose 13 precisely dated early medieval Spanish pottery fragments, four archaeological French kilns and three collections of bricks used for the construction of different French historical buildings with ages ranging between 335 and 1260 AD have been studied. Classical Thellier experiments performed on 164 specimens, and including anisotropy of thermoremanent magnetisation and cooling rate corrections, gave 119 reliable results. The 10 new high-quality mean archaeointensities obtained confirm the existence of an intensity maximum of $ 85 mT (at the latitude of Paris) centred at $ 800 AD and suggest that a previous abrupt intensity change occurred around 600 AD. Together with previously published data from western Europe that we deem to be the most reliable, the new data also suggest the existence of two other abrupt geomagnetic field intensity variations during the 12th century and around the second half of the 13th century AD. High-quality archaeointensities available from eastern Europe indicate that very similar geomagnetic field intensity changes occurred in this region. European data indicate that very rapid intensity changes (of at least 20 mT/century) took place in the recent history of the Earth's magnetic field. The results call for additional high-quality archaeointensities obtained from precisely dated samples and for a selection of the previously published data if a refined description of geomagnetic field intensity changes at regional scales is to be obtained.

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Section: French Kilns and Bricks Used For The Construction Of Historisupporting

confidence: 74%

Improving our knowledge of rapid geomagnetic field intensity changes observed in Europe between 200 and 1400 AD

Gómez‐Paccard

Chauvin

Lanos

et al. 2012

Earth and Planetary Science Letters

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“…The difference 90-INC is the angular deviation of the laboratory field from the carried NRM vector. As described in Kovacheva et al, (2009b) and as well known from the literature (Odah et al, 2001), this deviation is one of the main factors for the effect of the magnetic anisotropy during the PI evaluation. For example, on a subset of 44 brick specimens the 12 anisotropy effect on the PI evaluations has been studied using the TRM anisotropy tensor (18) or the ARM anisotropy tensor (26).…”

Section: Discussion Of the Raw Datamentioning

confidence: 72%

Extended and revised archaeomagnetic database and secular variation curves from Bulgaria for the last eight millennia

Kovacheva¹,

Kostadinova‐Avramova²,

Jordanova³

et al. 2014

Physics of the Earth and Planetary Interiors

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“…These values seem to be typical of baked clays, for example, Kovacheva et al (2009) reported that baked clay and soils collected from archeological sites in France and Bulgaria resulted in TRM anisotropy ratios less than 1.20 for about 80% of the collection. …”

Section: Tsunakawa-shaw Paleointensity Experimentsmentioning

confidence: 99%

Archeointensity study on baked clay samples taken from the reconstructed ancient kiln: implication for validity of the Tsunakawa-Shaw paleointensity method

Yamamoto

Torii

Natsuhara³

2015

Earth Planet Sp

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In 1972, a reconstruction experiment of a kiln had been done to reproduce an excavated kiln of the seventh century in Japan. Baked clay samples were taken from the floor surface and −20 cm level, and they have been stored after determinations of the paleomagnetic directions by partial alternating field demagnetizations. We recently applied the Tsunakawa-Shaw method to the samples to assess how reliable archeointensity results are obtained from the samples. A suite of the rock magnetic experiments and the scanning electron microscope observations elucidate that dominant magnetic carriers of the floor surface samples are Ti-poor titanomagnetite grains in approximately 10 nm size with single-domain and/or super-paramagnetic states, whereas contributions of multi-domain grains seem to be relatively large for the −20-cm level samples. From the floor surface samples, six out of the eight successful results were obtained and they give an average of 47.3 μT with a standard deviation of 2.2 μT. This is fairly consistent with the in situ geomagnetic field of 46.4 μT at the time of the reconstruction. They are obtained with a built-in anisotropy correction using anhysteretic remanent magnetization and without any cooling rate corrections. In contrast, only one out of four was successful from the −20-cm level samples. It yields an archeointensity of 31.6 μT, which is inconsistent with the in situ geomagnetic field. Considering from the in situ temperature record during the firing of the kiln and the unblocking temperature spectra of the samples, the floor surface samples acquired full thermoremanent magnetizations (TRMs) as their natural remanent magnetizations whereas the −20-cm level samples only acquired partial TRMs, and these differences probably cause the difference in the archeointensity results between the two sample groups. For archeointensity researches, baked clay samples from a kiln floor are considered to be ideal materials.

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Remanence anisotropy effect on the palaeointensity results obtained from various archaeological materials, excluding pottery

Cited by 40 publications

References 29 publications

Improving our knowledge of rapid geomagnetic field intensity changes observed in Europe between 200 and 1400 AD

Improving our knowledge of rapid geomagnetic field intensity changes observed in Europe between 200 and 1400 AD

Extended and revised archaeomagnetic database and secular variation curves from Bulgaria for the last eight millennia

Archeointensity study on baked clay samples taken from the reconstructed ancient kiln: implication for validity of the Tsunakawa-Shaw paleointensity method

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