Spot Reading of the Absolute Paleointensity of the Geomagnetic Field Obtained from Potsherds (Age Ca. 500-430 AD) in Teotihuacan, Mexico

Abstract

Archaeointensity data have been obtained successfully using the Thellier-Coe protocol from twelve potsherds recovered from the vicinity of the “Piramide del Sol”, Teotihuacan, Mexico. In order to understand the magnetic behavior of the samples, we have conducted low-field versus temperature (k-T) experiments to determine the magnetic carriers of the pre-Columbian artefacts, as well as Saturation Isothermal Remanent Magnetization (SIRM), hysteresis loops and back-fields TESTS. The Curie temperatures indicate the presence of at least three magnetic mineral phases (238°C - 276°C, 569°C - 592°C, and 609°C - 624°C). The predominant Curie temperatures for these samples are typical of Ti-poor magnetite. The results of the magnetic grain size analyses indicate that if the magnetic mineral in a sample is only magnetite, the distribution on the modified Day et al. (1977) diagram yields specimens in the Single (SD), Pseudo (PSD) and Superparamagnetic (SP) domain ranges. The successfully absolute paleointensity determinations in this study using the Thellier-Coe protocol have yielded an average paleointensity of 38.871 +/- 1.833 m-Teslas (N = 12), and a virtual geomagnetic dipole moment of 8.682 +/- 0.402 × 1022 A/m2 which is slightly lower than the present field strength and which corresponds to an age interval between 500 and 430 AD. Thus, our results correlate well with the recently published CALS3K.4 curve and the incipient archaeointensity reference curve for the Mesoamerican paleo-field results. Therefore, the age of the artefacts would correlate well with absolute the early classic Teotihuacan cultural period.