Archaeointensity study of pottery from the Maya settlements of La Blanca and Chilonché (Petén, Guatemala): New data to constrain the geomagnetic field evolution in Central America

Abstract

Accurate determination of the spatio-temporal variation of the geomagnetic field before direct measurements relies on reliable archaeomagnetic data. This study presents new archaeointensity data from Central America, a region with paucity of archaeomagnetic data. We specifically investigate 71 Maya pottery fragments collected at the “La Blanca” and “Chilonché” archaeological sites in Guatemala, with ages ranging between 600 and 1100 CE. We employed the classical Thellier-Thellier palaeointensity method, including partial thermoremanent magnetization (pTRM) checks, TRM anisotropy, and cooling rate corrections at the specimen level. Out of 252 specimens analyzed, only 50 from 14 fragments yielded successful results. The fragment-mean intensities obtained meet modern standards and are considered technically robust. Our findings indicate significant variability even among samples from the same period, likely due to age disparities among fragments, undetected issues in magnetic properties of the analyzed potteries and fluctuations in geomagnetic intensity. To better understand this variability, acquiring new data with higher precision dating, ideally at multi-decadal intervals, is essential. A comparison with selected previous palaeointensities, regional palaeosecular variation curves from Mexico, and global geomagnetic field models' predictions confirms that the current understanding of geomagnetic field strength evolution in Central America is unsatisfactory due to the low number of archaeomagnetic data and their significant dispersion. In this context, new high-quality palaeointensity data are required to serve as a constrain for establishing the geomagnetic field behavior in Central American during the first millennium CE and to contribute improving regional and global geomagnetic field reconstructions.