Abstract

LOPEZ, Verónica et al. From Chupícuaro to the depopulation of the northern border. Archeomagnetic evidence from the Lo de Juárez site, Guanajuato, Mexico. Bol. Soc. Geol. Mex [online]. 2021, vol.73, n.1, 00013.  Epub Oct 11, 2021. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2021v73n1a050121.

Significant progress in archeomagnetic studies over the past decade suggests that magnetic dating may be a valuable tool jar reconstructing chronologies of firing structures. Despite important works with numerous findings of great regional impact, the absolute chronology of archaeological sites in the state j Guanajuato is supported by few reliable data. The archaeological rescue intervention carried out in the city of Irapuato, offered a unique opportunity to analyze a perfectly preserved stove and oven, considered to be excellent means of recording the Earth's Magnetic Field at the time of its last use. The magnetic experiments carried out included: determination of hysteresis cycles, acquisition of the isothermal remanent magnetization, continuous thermomagnetic curves, demagnetization by alternating fields and determination of the absolute geomagnetic intensities. Titanium-poor titanomagnetite emerges as the main magnetic carrier while its domain state corresponds to pseudo-single structure. Characteristic directions were obtainedfor both structures analyzed with reasonable precision. However, the absolute archaeointensity was obtained only for the furnace samples (Structure 2). The result of archeomagnetic dating for the stove showed an interval of time between AD 973 and 1204. Instead, the dating of the presumably limekiln provided an age interval between 36 B.C. and AD 40. These data open a new panorama in the .study of the earliest occupations that occurred in this sector of the Bajío. Despite the existence of reports of Chupícuaro-style ceramics near the area, there are no supported absolute dates that corroborate these new dates of occupation. When comparing the obtained results with the chronologies, it seems that the Lo de Juárez site is contemporaneous to the Mixtlán and so-called Interphase phases. At the same time, the stove is located in the early post-classic period. These new absolute chronological contributions open new questions regarding the occupation phases of the regional pre-Hispanic population, specifically, the Guanajuato River Basin.

Keywords : archaeomagnetism; Guanajuato; Chupícuaro; Bajío tradition; absolute dating; regional geoarchaeology; Guanajuato river basin.