A comprehensive paleomagnetic study from the last Plinian eruptions of Popocatepetl volcano: absolute chronology of lavas and estimation of emplacement temperatures of PDCs

摘要

Abstract Three lava flows (Buenavista, Xalitzintla and Nealtican) and pyroclastic density currents (Lorenzo and Pink Pumice) from two Popocatepetl Plinian eruptions were sampled for paleomagnetic dating. A detailed rock-magnetic characterization of the lavas, scoria clasts and pottery shards intercalated between the volcanic deposits was also carried out. Reliable results, both in direction and in intensity, were obtained for the Nealtican lava flow, which enabled its full-vector paleomagnetic dating using the archaeo_dating tool together with the global paleosecular variation model SHA.DIF.14 k, obtaining an age interval between 1040 AD and 1140 AD (95% probability confidence level), in good agreement with its associated 14C age. The well-grouped paleomagnetic direction of the seven specimens from two different scoria clasts of the Lorenzo Pumice pyroclastic density current suggests that clasts were emplaced hot, at a temperature that seems to have almost completely erased the original remanent magnetization of the clasts. This fact is supported by the reheating of the underlying pottery shards, evidenced as a clear secondary low-temperature range (room temperature to 350 °C) component at the orthogonal vector plots. Similarly, the three mean clusters directions obtained for site PO-2 (Pink Pumice)—roughly concentrated around the present geomagnetic field—suggest also a high emplacement temperature. Also, the first archeointensity dating of a pottery shard within the pyroclastic density current is reported. Finally, results of the rock-magnetic and paleomagnetic dating of the last Plinian eruptions from the Popocatepetl volcano, applied to different volcanic materials (lava and pyroclastic density currents), show the usefulness of these nonconventional and alternative techniques in the study of the eruptive activity of volcanoes. Graphic abstract .