Tracing the ritual fire in La Quemada (Northern Mesoamerica)

Abstract

Recent advances in absolute chronology studies on the northern border of Mesoamerica have been driven by archaeomagnetic surveys of burned artifacts. However, reliable data from the structures remain limited. La Quemada (The Burned) archaeological site is the most important regional, essentially ceremonial centre at the northern border of Mesoamerica. A series of fire pits (here referred to as LQ1 to LQ5) likely served as ceremonial torches to illuminate rituals. One hundred oriented specimens from five previously excavated fire pits were subjected to step-wise alternating field demagnetization of the natural remanent magnetization, while double-heating, Thellier absolute geomagnetic intensity experiments were performed on another 50 specimens. Magnetic mineralogy is mainly dominated by magnetite (or Ti-poor titanomagnetite) and hematite in less proporsions. The mean directions were obtained from four sites, while only one fire pit provided reliable archaeointensity values. A combination of global geomagnetic models and available regional reference curves was used for the archaeomagnetic dating. Three of the four structures yielded statistically indistinguishable intervals, indicating the La Quemada phase (650–900 CE) as the most probable period for their last exposure to fire. Absolute age estimates for the fire pit LQ1, based on various models and local paleosecular variation patterns, show strong agreement within 927–1101 CE, aligning with the last Ciudadela phase just prior to the second stage of site abandonment. For the LQ2 fire pit, the intervals obtained from models and local curves are not concordant, while no results were obtained for the fire pit LQ3. Almost similar age intervals were obtained for the LQ4 and LQ5 fire pits, 719–903 CE and 675–895 CE, respectively. A very early age was obtained for these sites using the SHA.DIF.14 k model and age corresponding to Malpaso occupational phase using the SHAWQ.2 k model. However, the local paleosecular variation curves indicate the La Quemada phase within 625–775 CE. The age interval obtained for the site LQ1 (closest fire pit to the Votive Pyramid) agrees reasonably well with the period of depopulation of the site, implying that some specific rituals persisted at the last stage of the site related to the La Quemada’s subsequent decline and abandonment, most probably due to environmental causes.