Fire Along the Street of the Dead: New Comprehensive Archaeomagnetic Survey in Teotihuacan (Central Mesoamerica)

Teotihuacan, one of the most significant urban and ceremonial centers of ancient Mesoamerica, was abruptly abandoned in the mid-1st millennium AD. The cause and timing of its collapse—commonly placed between 600 and 650 AD—remain major questions in Mesoamerican archaeology. In this study, we present a new archaeomagnetic investigation of six burned structures distributed along the Street of the Dead, including sites at the Square of the Moon, the Room of Columns, the Northwest Complex of the San Juan River, the Superimposed Buildings, and the West Plaza. Magnetic analyses revealed pseudo-single-domain magnetite as the main remanence carrier and produced well-grouped paleodirections (site-mean declinations ranging from 341.1° to 1.7°, α95 ≤ 3.6°) and reliable absolute paleointensities (ranging from 39.4 ± 3.4 μT to 52.5 ± 5.4 μT), obtained using the Thellier-type double-heating method. Archaeomagnetic dating using both global geomagnetic models (SHAWQ.2k) and regional secular variation curves suggests that the last heating events at these sites occurred between ~400 and 500 AD—well before the traditionally cited Metepec phase (550–650 AD) and the so-called “Great Fire.” These findings challenge the prevailing chronological framework and provide compelling evidence that major episodes of destruction and depopulation may have begun earlier than previously recognized.