Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: www.elsevier.com/locate/jasrep The memory of fire in El Coporo (Northern Mesoamerica): Apogee and abandonment Alejandra García Pimentel a , Avto Goguitchaichvili a, ⁎ , Carlos Torreblanca b ,RubénCejudoRuiz a , Vadim Kravchinsky c , Rafael García a , Juan Morales a , Miguel Cervantes a a Servicio Arqueomagnético Nacional (SAN), Instituto de Geofísica, UNAM, Unidad Michoacán, Campus Morelia, Antigua Carretera a Pátzcuaro No. 8701 Col. Ex‑Hacienda de San José de la Huerta, 58190 Morelia, Michoacán, Mexico b INAH Zacatecas, Mexico c Geophysics, Department of Physics, University of Alberta, Edmonton, Alberta T6G2E1, Canada ARTICLEINFO Keywords: Mesoamerica Absolute chronology Archaeomagnetism Mexico Guanajuato El Coporo ABSTRACT Most detailed archaeometric studies come from central and southern Mesoamerica while many important sites belonging to the western regions are not yet rigorously studied. Here we report a detailed rock-magnetic and archaeomagneticstudyfromtheElCoporoarchaeologicalsiteatthenorthernborderofMesoamerica.Ourstudy of more than 100 oriented samples was performed on the six most important sites distributed along the ar- chaeological zone. Continuous thermomagnetic curves revealed magnetite as responsible for magnetization accompanied by unstable (titano)maghemite. Most of the samples are characterized by a single component magnetization,whichisalmostcompletelyremovedapplying50mT,suggestingthepresenceofrelativelylow coercivity magnetic minerals. Characteristic directions were precisely determined for four out of six studied sites, yielding statistically undistinguishable directions. Corresponding archaeomagnetic age intervals range from 820 to 950 A.D. in good agreement with previous archaeological studies that suggested a period of abandonment at about 900 A.D. as an attempt to reoccupy the place by the Toltecs. Numerous archaeological evidences argue in favor of an intentional fire. However, the possibility of ritual closure should be also con- sidered since there is no evidence of violent or warlike actions. 1. Introduction Mesoamerica is a cultural region that includes the central and southern territories of Mexico together with Guatemala, Belize, El Salvador,westernHondurasandNicaraguawherevariouspre-Hispanic cultures such as the Olmecs, Toltecs, Teotihuacanos, Zapotecs, Aztecs, Mixtecs and Mayas developed. In Mexico, the northern border of this cultural region includes the states of Michoacán, Guanajuato, Jalisco, Mexico and partly Veracruz. The chronology of Mesoamerica is com- prised within three great intervals: the Preclassic period, which begins around 2000 BC and ends approximately 300 AD; the Classic period between 300 and 900 AD and the Postclassic period that comprises from 900 AD to 1521 AD. This chronology is based on stratigraphic sequences based mainly on pottery and architectural styles. ThefirstarchaeomagneticinvestigationsinMexicowerecarriedout by Nagata et al. (1965), who determined the absolute geomagnetic paleointensities on pottery samples from Cuicuilco in the south of Mexico City, and on basalts and pyroclastic rocks of the Xitle historic eruptions (Soler-Arechalde, 2006). Daniel Wolfman in 1969 analyzed the first samples for archaeomagnetic dating proposing an updated chronologyforMesoamericabetween0and1200AD. Wolfman(1973) considered chronological order of the geomagnetic virtual poles based mainly on stratigraphy and pottery style and very few available 14 C dates, recognizing that they were insufficient for an adequate descrip- tionofthesecularvariationofthegeomagneticfield.Thesitesstudied byWolfmanarelocatedincentralMexico,theOaxacavalley,Zapotal, central and western Chiapas, Guatemala and Honduras (Soler- Arechalde, 2006). Archeomagnetic studies increased considerably during the last two decades, allowing to expand the range of arche- ological artifacts, as presented by the study of Goguitchaichvili et al. (2004), who analyzed four Mesoamerican wall paintings, from which the direction of its remnant (pictorial) magnetization was determined successfully.Thisisconsideredapioneeringworkinthedetermination of archeodirections for Mesoamerican murals containing reddish pig- mentation. Apparently, a mixture of magnetite and hematite is re- sponsible for magnetization (Goguitchaichvili, 2018). Morales et al. https://doi.org/10.1016/j.jasrep.2020.102274 Received 12 September 2019; Received in revised form 17 January 2020; Accepted 28 January 2020 ⁎ Corresponding author. E-mail address: avto@igeofisica.unam.mx (A. Goguitchaichvili). Journal of Archaeological Science: Reports 30 (2020) 102274 2352-409X/ © 2020 Elsevier Ltd. All rights reserved. T