Paleomagnetic constraints on the ages of the Holocene Malpaís de Zacapu lava flow eruptions, Michoacán (México): Implications for archeology and volcanic hazards
Résumé
"Four monogenetic Holocene lava flows located within the Michoacán-Guanajuato Volcanic Field, Mexico, were sampled for paleomagnetic dating. These flows (namely, El Infiernillo, Malpaís Las Víboras, El Capaxtiro, and Malpaís Prieto) are within the heartland of the pre-Hispanic Tarascan civilization and were inhabited repeatedly since at least 100 BC, but no relation with the volcanic evolution has been proposed so far. The stratigraphically oldest lava flow, El Infiernillo, has a radiocarbon age of 3200 ± 30 yr BP (cal. 1525–1420 BC), and it was used to validate the method. Using full-vector paleomagnetic data from three sites as input for paleomagnetic dating applying the global paleosecular variation model SHA.DIF.14k, an age range of 1500–1370 BC was obtained. Two age ranges of 1340–1230 and 1030–940 BC were obtained for Malpaís Las Víboras. A younger age range of 200–80 BC was obtained for the Capaxtiro lava flow and, finally, the Malpaís Prieto lava flow erupted within the range of AD 830–960. The human occupation history of these flows started around 100 BC during the late Pre-Classic, probably shortly after the Capaxtiro eruption. Archeological records indicate an abandonment of the entire area around AD 900 (late to terminal Classic), which coincides with the paleomagnetic age of the Malpaís Prieto eruption. Interestingly, this area was heavily repopulated again only few hundred years later around AD 1250 and belongs to the core region in which the Tarascan civilization has its roots. The eruption recurrence interval of roughly 1000 years indicates that a new monogenetic eruption should be expected to occur again in the future and that this area deserves to be studied in greater detail with particular emphasis on the impact of past eruptions. This could help to better evaluate volcanic hazards and design preparedness strategies to minimize the impact of a future eruption." (source éditeur)