Paleomagnetic dating of the most recent silicic eruptive activity at Pantelleria (Strait of Sicily) |
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| Authors: | Fabio Speranza Patrizia Landi Francesca D’Ajello Caracciolo Alessandro Pignatelli |
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| Institution: | (1) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma 2, Via di Vigna Murata 605, 00143 Rome, Italy;(2) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola 32, 56126 Pisa, Italy |
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| Abstract: | We report on the paleomagnetism of ten sites in the products of the most recent silicic eruptive cycle of Pantelleria, Strait
of Sicily. Previously radiometrically dated at 5–10 ka, our comparison with proxies for geomagnetic field directions allows
us to narrow considerably the time window during which these eruptions occurred. The strongly peralkaline composition causes
the magmas to have low viscosities, locally resulting in strong agglutination of proximal fall deposits. This allows successful
extraction of paleomagnetic directions from the explosive phases of eruptions. One of our sites was located in the Serra della
Fastuca fall deposit, produced by the first explosive event of the eruptive cycle. The other nine sites were located in the
most recent explosive (pumice fall and agglutinate from Cuddia del Gallo and Cuddia Randazzo) and effusive (Khaggiar lava)
products. The (very similar) paleomagnetic directions gathered from eight internally consistent sites were compared to reference
geomagnetic field directions of the last 5–10 ka. Directions from Cuddia del Gallo agglutinate and Khaggiar flows translate
into 5.9- to 6.2-ka ages, whereas the Fastuca pumices yield a slightly older age of 6.2–6.8 ka. Hence, the most recent silicic
eruptive cycle lasted at most a millennium and as little as a few centuries around 6.0 ka. Paleomagnetically inferred ages
are in good agreement with published (and calibrated by us) 14C dates from paleosols/charcoals sampled below the studied volcanic units, whereas K/Ar data are more scattered and yield
∼30% older ages. Our data show that the time elapsed since the most recent silicic eruptions at Pantelleria is comparable
to the quiescence period separating the two latest volcanic cycles. |
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