Integrated archeomagnetic and micro–Raman spectroscopy study of pre‐Columbian ceramics from the Mesoamerican formative village of Cuanalan, Teotihuacan Valley, Mexico

Abstract

[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 mT, and corresponding virtual axial dipole moments range from 4.8 ± 0.6 to 8.0 ± 0.4 (10 22 A m 2 ). This corresponds to a mean virtual dipole moment value of 5.9 ± 1.1 Â 10 22 A m 2 , 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.

Magnetic properties and Archeointensity of Earth’s magnetic field recovered from El Opeño, earliest funeral architecture known in Western Mesoamerica

“…9) is the intensity obtained at about 200 B.C. (Rodriguez-Ceja et al, 2009) which should be confirmed by further investigations. …”

“…The mean archeointensity obtained in the present study agrees reasonably well with the predicted absolute intensities retrieved from CALS7K global model. Other available Mesoamerican data however differ from this model (Rodriguez-Ceja et al, 2009). It should be noted that many archeoinintensity determinations used in Korte and Constable's (2005) model are not corrected for cooling rate and remanence (TRM) anisotropy.…”

“…Several rock- 9. Currently available absolute intensity data from Mesoamerica derived from archeological artifacts and historic lava flows (this study and Rodriguez-Ceja et al, 2009). Also shown are the data derived from Korte and Constable's (2005) CALS7K.2 model prediction between 2000 to 1000 BC together with CALS3k.3, SED3K and ARCH3K curves .…”

“…It should be noted that the cooling rate correction was applied only when the corresponding change in TRM acquisition capacity was below 15%. The samples yielding higher values are generally thermally altered (Rodriguez-Ceja, 2009). Anisotropy of TRM is determined following the procedure of McCabe et al (1985) at the end of Thellier-Thellier cycle.…”

“…Apart from pioneering studies carried out in the 60's (Nagata et al, 1965;Bucha et al, 1970) no systematic measurements were performed until very recently. studied some Pre-Columbian pottery from Chiapas while Rodriguez-Ceja et al (2009) reported a detailed rock-magnetic and archeointensity investigation from the Mesoamerican formative village of Cuanalan, Teotihuacan Valley. The number of analyzed samples, however, is still not numerous and ages are poorly constrained.…”