An inter-comparison exercise for the Mexican intensity secular variation curves: Case study of the Tingambato archaeological site (central-western Mexico)

Dating analysis of potsherds from three of the six units recently excavated in the Tingambato archaeological site, central-western Mexico, was carried out employing two regional intensity Paleosecular Variation Curves (PSVC) and the global model SHA.DIF.14k. A complete evaluation of the ceramic fragments' magnetic characteristics was done to determine the samples' magnetic carriers and their capacity to provide reliable archaeointensity data. The presence of two magnetization components in five analyzed potsherds provides two snapshots of the Earth's magnetic field intensity behavior at different temporalities. Intensity values were obtained following strict quality criteria, including cooling rate and anisotropy corrections. The principal causes of failure in archaeointensity experiments are associated with the alteration of the magnetic mineralogy during the heating of the specimens and with the presence of multidomain grains. Intensities within the established quality criteria were obtained for four out of the eleven ceramic fragments analyzed. The dating exercise shows a better correspondence of the intensity values with the regional curves than with the global model, especially for the temporal range between AD 400-1200, for which both regional curves are in good agreement. The obtained archaeomagnetic ages had a good correspondence with the radiocarbon ages reported in previous studies. By determining two archaeointensity values in one of the studied potsherds: one associated whit its fabrication and the other related to the fire (after which the site is supposed to be abandoned), archaeomagnetic ages of the probable end of Tingambato occupation were estimated.