Archeomagnetism of Jesuit Missions in South Brazil (1657–1706 AD) and assessment of the South American database

Poletti, Wilbor; Trindade, R. I.; Hartmann, Gelvam A.; Damiani, Nadir; Rech, Raquel M.

doi:10.1016/j.epsl.2016.04.006

Cited by 28 publications

(49 citation statements)

References 45 publications

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“…Concerning our new Chalcatzingo data, 21/23 respect these criteria; the two sherds (CHAL019 and CHAL132) are discarded because only two successful archaeointensities were obtained by sherd Most other Mexican data were corrected for anisotropy effects with the Mean (XYZ) method, averaging the archaeointensities of six specimens from the same sample, for which the laboratory field during the Thellier experiments was applied along +x, −x, +y, −y, +z, or −z axis, respectively. As demonstrated by the experimental tests of and Poletti et al (2016), this method leads to systematic larger imprecisions and to possible inaccuracies of more than 10 μT. In , we decided to retain such archaeointensities if they were calculated with six specimens, because the balanced participation of the three x, y, and z axes reduces the risk of inaccuracy.…”

Section: 1029/2019gc008668mentioning

confidence: 99%

Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

Hervé

Perrin

Alva‐Valdivia

et al. 2019

Geochem Geophys Geosyst

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In Western Eurasia, the first millennium BCE is characterized by the fastest secular variation of the Earth Magnetic Field observed over the last millennia and by a geomagnetic anomaly centered on the Middle East. On the global scale, the variation of the dipolar field during this period remains poorly constrained because of the lack of data in other geographical areas. Here, we presented 23 new mean archaeointensity data on ceramic sherds dated between 1500 BCE and 200 CE from Chalcatzingo archaeological site in Central Mexico. Archaeointensities were determined using the classical Thellier-Thellier protocol with corrections for TRM anisotropy and cooling rate effects. Our work doubles the number of high-quality archaeointensity data in Mexico during the considered period. Using a Bayesian approach, a new secular variation curve was calculated at Mexico City between 1500 BCE and 200 CE after selection of Mexican archaeointensity data. After a period of oscillations of the intensity between 20 and 40 μT from 1500 to 300 BCE, the curve shows a large maximum`~65 μT in the second century BCE. The corresponding VADM varied between~4.0 and~11.0 × 10 22 Am 2 , which highlights further that the intensity of the geomagnetic field could vary at regional scale over a larger range as previously thought. However, this amplitude variation may be overestimated, as it does not take into account the fast directional variation observed at this time.Plain Language Summary Archaeological baked clays are the best material to reconstitute the past secular variation of the Earth magnetic field, because they acquired a generally stable thermoremanent magnetization usually parallel and proportional to the ambient field at the time of their baking. Global modeling of the geomagnetic field requires a spatial and temporal distribution of data as homogeneous as possible, which is still not the case yet. In spite of its rich archaeological heritage, high-quality archaeointensity data are still very few in Mexico. The present study focuses on pottery sherds dated between 1500 BCE and 200 CE from Chalcatzingo archaeological site in Central Mexico. We obtained 21 new mean archaeointensities, which almost doubles the high-quality Mexican dataset for this period. The new secular variation Mexican curve exhibits oscillations of the intensity between 20 and 40 μT from 1500 to 300 BCE, before a large maximum~65 μT in the second century BCE. This work will help to have a better knowledge of the variation of the dipolar geomagnetic field during the first millennium BCE, when the fastest secular variation over the last millennia was reported in the Middle East ("geomagnetic spikes").

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Section: 1029/2019gc008668mentioning

confidence: 99%

Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

Hervé

Perrin

Alva‐Valdivia

et al. 2019

Geochem Geophys Geosyst

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“…S+SE-Brazil+Argentina results also plot systematically below the relocated data from NE Brazil and Chile. Relative to the studied region, NE Brazil results are located ~15° to the north and results from Chile are located ~10°/15° to the south/west Poletti et al (2016) ______________________________________________________________________ 41 ( Fig. 2.2.5).…”

Section: Trends and Gaps Of High-quality Archeointensity Data For Soumentioning

confidence: 93%

“…The methods used in this thesis to acquire new results are the modified Thellier-Thellier and the Microwave (see below). The other methods were only taken into account during the reassessment of published results (details in Poletti et al, , 2016Poletti et al, and 2018).…”

Section: Secular Variation In the Southern Hemispherementioning

confidence: 99%

“…Selection criteria" - Poletti et al, 2018) (details about the selection criteria of new archaeointensity results in "3.3. Selection criteria" - Poletti et al, 2016). Paterson et al, 2012).…”

Section: Theory Of Ancient Intensity Estimationmentioning

confidence: 99%

“…Tarduno et al, 2015). In South America, in an attempt to improve the archeomagnetic database, several studies were performed in the past decade addressing the variability of the field in the region in the past millennia Roperch et al, 2014Poletti et al, 2016;Di Chiara et al, 2017). A critical assessment of the South American archeointensity database selected only 39 highquality data for the region, most of them within the past 700 years (Poletti et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Archaeomagnetic field intensity evolution during the last two millennia

Silva¹

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Paulo pelo espaço a mim concedido, e também a todos os seus funcionários. Em especial, agradeço às técnicas Daniele Brandt e Sônia Alonso e ao técnico Giovanni Moreira por todo o suporte. Agradeço a todos aqueles que de alguma forma fizeram, ou ainda fazem, parte do USPMag: alunos de iniciação científica, mestrandos, doutorandos, pós-doutorandos, técnicos e professores. Em especial, aos colegas: Agradeço aos meus colega de pós-graduação do Departamento de Geofísica (USP) pelo convívio e ambiente agradável. Agradeço também imensamente aos membros e aos agregados da Sala-E208 do Departamento de Geofísica (USP) por me aguentarem e, principalmente, por toda conversa! Ressalto meus agradecimentos à Karine Carvas, minha grande amiga e por muitas vezes "psicóloga"! Agradeço ao meu irmão e parceiro, Clodoaldo Poletti, por todo o incentivo e força durante meu doutorado. Foram inúmeras as vezes em que ele me impulsionou quando eu titubeei. Sem dúvidas, um dos pilares mais fortes desse caminho. Agradeço à minha mãe, Ivane Poletti, por nunca deixar de me apoiar nos momentos em que me faltaram forças. Por me transmitir segurança e me tranquilizar, mesmo no momento em que vivia sua maior adversidade. E também, pela sua garra e, principalmente, por todo seu amor. Agradeço à minha parceira no crime, Grasiane Mathias. A intensidade na qual eu desenvolvi o meu doutorado foi apenas um reflexo da intensidade de minha vida pessoal, proporcionada justamente pela Grá. No período de um doutorado, nós namoramos, casamos, tivemos uma filha (que, por sua vez, me mostrou o que realmente é a vida!), moramos em outro país, nos permitimos e evoluímos. Hoje somos um time de três (Grá, Alice e eu) e somos mais fortes, como consequência direta do que vivemos juntos. A ciência não seria para mim tão bela e reveladora se Grá e Alice não fossem o filtro delicado de parte de minha miopia!iii Abstract ______________________________________________________________________ Temporal variations of Earth's magnetic field provide a great range of geophysical information about the dynamics at different layers of the Earth. Since it is a planetary field, regional and global aspects can be explored, depending on the timescale of variations. In this thesis, the geomagnetic field variations for the last two millennia were investigated. For that, some improvement on the methods to recover the ancient magnetic field intensity from archeological material were done, new data was acquired and a critical assessment of the global archaeomagnetic database was performed. Two methodological advances are reported, comprising: i) the correction for microwave method of the cooling rate effect, which is associated to the difference between the cooling times during the manufactory of the material and that of the heating steps during the archaeointensity experiment; (ii) a test for thermoremanent anisotropy correction from the arithmetic mean of six orthogonal samples. The temporal variation of the magnetic intensity for South America was investigated from nine new data, three ...

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