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

• Published in: Studia geophysica et geodaetica 2010-10, Vol.54 (4), p.575-593
• Main Authors: Duran, Modesto Pineda, Goguitchaichvili, Avto, Morales, Juan, Reyes, Bertha Aguilar, Valdivia, Luis M. Alva, Oliveros-Morales, Arturo, Calvo-Rathert, Manuel, Moran, Tomas Gonzalez, Robles-Camacho, Jasinto
• Format: Article
• Language: English
• Subjects: Anisotropy; Archaeological sites; Atmospheric Sciences; Earth; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Magnetic fields; Magnetic properties; Structural Geology
• ISSN: 0039-3169; 1573-1626
• DOI: 10.1007/s11200-010-0035-5

Despite of the impressive cultural heritage and abundant archaeological sites, absolute geomagnetic intensity data from Mesoamerica are still sparse. Archeointensity determinations using the Coe variant of the Thellier and Thellier method have been carried out on some selected pottery fragments from the El Opeño archeological site which has the earliest funeral architecture known in western Mesoamerica. The El Opeño chronology is supported by six C 14 datings performed on carbon-bearing materials. Detailed rock magnetic experiments including susceptibility vs. temperature curves, hysteresis cycles and thermal demagnetization procedures were carried out in order to estimate the magnetic carriers and their stability. Cooling rate and anisotropy remanence corrected intensity values range from 25.0 ± 2.3 to 40.2 ± 3.0 μT and corresponding virtual axial dipole moments (VADM) range from 5.6 ± 0.5 to 8.9 ± 0.7 × 10 22 Am 2 . In addition, we present here a new compilation and analysis of existing absolute intensity data in order to try to estimate the variation of the Earth’s magnetic field over the past three millennia. The mean archeointensity obtained in the present study agrees reasonably well with the predicted absolute intensities retrieved from the CALS7K main field model. Other available Mesoamerican data, however, differ from this model. Most of available archeointensity data from Mesoamerica agree reasonably well with the ARCH3K main field model prediction. The broad peak defined at about 50 A.D. by our data is also predicted by the CALS3k.3 main field model but slightly displaced to the right while two smaller peaks are observed on the ARCH3K curve for the same time interval. The intensity value obtained at about 200 B.C. is a clear outlier and thus its geomagnetic significance should be confirmed by further investigations.