Integrated archeomagnetic and micro–Raman spectroscopy study of pre‐Columbian ceramics from the Mesoamerican formative village of Cuanalan, Teotihuacan Valley, Mexico
| Autor: | Mikhail Ostrooumov, Jaime Urrutia-Fucugauchi, Bertha Aguilar Reyes, María Rodríguez Ceja, Linda Manzanilla, Juan Morales, Avto Goguitchaichvili |
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| Rok vydání: | 2009 |
| Předmět: |
Atmospheric Science
Materials science Ecology Thermoremanent magnetization Paleontology Soil Science Mineralogy Forestry Aquatic Science Oceanography Rock magnetism chemistry.chemical_compound Magnetization Dipole Geophysics chemistry Space and Planetary Science Geochemistry and Petrology Ferrimagnetism Earth and Planetary Sciences (miscellaneous) Anisotropy Spectroscopy Earth-Surface Processes Water Science and Technology Magnetite |
| Zdroj: | Journal of Geophysical Research. 114 |
| ISSN: | 0148-0227 |
| DOI: | 10.1029/2008jb006106 |
| Popis: | [1] We report a detailed archeomagnetic and micro–Raman spectroscopy investigation on pre-Columbian pottery fragments from Cuanalan (a formative village in the valley of Teotihuacan, central Mexico). Available radiocarbon ages range from 2320 ± 80 to 2060 ± 90 B.P. Continuous low-field susceptibility versus temperature curves performed in air indicate Ti-poor titanomagnetites as magnetization carriers. Few samples, however, show two ferrimagnetic phases with Curie temperatures compatible with both Ti-poor and Ti-rich titanomagnetites. Hysteresis parameter ratios fall essentially in the pseudosingle-domain region, which may indicate a mixture of multidomain and a significant amount of single-domain grains. Mineralogical composition of the Teotihuacan ceramics has been investigated using micro–Raman spectroscopy. Samples are characterized by highly heterogeneous body matrix mineralogy due to the presence of a large variety of minerals with several mineralogical phases. Observed titanomagnetite and magnetite bands shift toward higher wave numbers, confirming a reducing atmosphere and a relatively high temperature (about 800–900°C) during the ceramic production. This definitively indicates the thermoremanent origin of magnetic magnetization. Archeointensity values have been determined from 7 pottery fragments (47 samples) out of 10 (70 samples) analyzed. Anisotropy of thermoremanent magnetization and the cooling rate effect upon thermoremanent magnetization intensity acquisition have been investigated in all the samples. The mean archeointensity values obtained in this study range from 24.2 ± 3.2 to 40.0 ± 1.7 μT, and corresponding virtual axial dipole moments range from 4.8 ± 0.6 to 8.0 ± 0.4 (1022 A m2). This corresponds to a mean virtual dipole moment value of 5.9 ± 1.1 × 1022 A m2, which is lower than the present-day field strength and the predicted values by global models and the latest data compilation. However, our data agree well with currently available absolute intensity values from Mesoamerica. The archeointensity values uncorrected for cooling rate and anisotropy are systematically higher than the corrected values. These uncorrected values agree with the CALS7K model, which may be biased by the fact that such corrections were not applied to most of the previous data. |
| Databáze: | OpenAIRE |
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