Age of Holocene lava flows of Pico de Orizaba from paleomagnetic data

High-precision paleomagnetic dating offers an independent and valuable tool for constraining the ages of Holocene volcanic eruptions - particularly when other dating methods are inapplicable yield uncertain results, or are contradicted by inconsistent historical records. We applied this approach to Pico de Orizaba (Citlaltépetl), a 5653 m stratovolcano in eastern Mexico that poses a significant threat to nearly half a million people living within a 30 km radius. Despite the existence of hazard maps, the eruptive chronology of the volcano remains poorly constrained due to contradictory and uncertain published data.

The study focused on Holocene lava flows, with sampling conducted at 35 sites across 12 distinct flows located at elevations between 3500 and 4800 m. We obtained robust paleomagnetic directions and absolute paleointensity values, which were compared to the SHA.DIF.14 k global geomagnetic model. This comparison enabled us to determine well-constrained emplacement ages, further supported by the available relative stratigraphic information.

Our results refine the Holocene eruptive history of Pico de Orizaba. We correlated two lava flows with previously determined 36Cl exposure ages, rejected earlier proposed historical attributions, and establish new correlations between flows on the northern and southern flanks. The eruptive record reveals two distinct phases interrupted by activity at the parasitic Chichimeco dome complex: (1) the Malacara lava flows, which followed the Citlaltépetl/Xilomich Plinian eruption, and (2) eruptions from approximately 2100 BCE to recent times. Both phases broadly coincide with periods of glacier retreat, suggesting a possible link between deglaciation and volcanic activity. These findings significantly improve the eruptive chronology of Pico de Orizaba and provide critical data for future hazard assessments.