Boletín de la Sociedad Geológica Mexicana Volumen 72, núm. 1, 2020, p. 1-18 http://dx.doi.org/10.18268/BSGM2020v72n1a260919

Fechamiento de flujos de lava del Holoceno tardío en el volcán Citlaltépetl (Pico de Orizaba) mediante el isótopo cosmogénico ³⁶Cl y liquenometría e implicaciones para la cronología eruptiva

Dating the late Holocene lava flows of the Citlaltépetl volcano (Orizaba Peak) by means of the ³⁶Cl cosmogenic isotope and lichenometry, and implications on eruptive chronology

Jesús Alcalá-Reygosa^1,*, Lorenzo Vázquez-Selem², José Juan Zamorano²

¹Facultad de Filosofía y Letras, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Coyoacán, CDMX, México.

²Instituto de Geografía, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Coyoacán, CDMX, México.

* Autor para correspondencia: (J. Alcalá Reygosa) 

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Cómo citar este articulo: Alcalá-Reygosa J., Vázquez-Selem L., Zamorano J. J., 2020, Fechamiento de flujos de lava del Holoceno tardío en el volcán Citlaltépetl (Pico de Orizaba) mediante el isótopo cosmogénico ³⁶Cl y liquenometría e implicaciones para la cronología eruptiva: Boletín de la Sociedad Geológica Mexicana, 72 (1), A260919. http://dx.doi.org/10.18268/BSGM2020v72n1a260919

Abstract

In this study we tested whether young (Holocene) lava flows can be confidently dated based on the preservation of the primary geomorphological features, the stratigraphic position and historical records. To verify this hypothesis, we combined in situ-produced cosmogenic ³⁶Cl exposure dating and lichenometry on two lava flows from the last eruptive cycle of Citlaltépetl (Pico de Orizaba), called Lava flow “A” and “B”, previously attributed to 16th and 17th century eruptions, respectively. On lava flow “A”, the measured in situ-produced ³⁶Cl concentrations lead to a mean age of 3.03 ± 0.70 ka, while lichenometry yields a minimum age of ~1,130 years. Regarding lava flow “B”, the measured in situ-produced ³⁶Cl concentrations lead to a mean age of 1.45 ± 0.35 ka, whereas lichenometry gives a minimum age of ~1,000 years. The exposure ages derived from these methods indicate that both lava flows are significantly older than previously thought and therefore the combination of the preservation of the primary geomorphological features, the stratigraphic position and the historical records is not enough to determine their ages. Overall, the combination of in situ-produced ³⁶Cl cosmic ray exposure dating and lichenometry, used for the first time in Mexico and supported by geomorphological, stratigraphic and historical record criteria, has a considerable potential for dating purposes and it could be useful to refine the eruptive history of other Mexican volcanoes.

Keywords: Lava flows, in situ-produced cosmogenic ³⁶Cl, lichenometry, lichen Rhizocarpon geographicum, Late Holocene.