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[1] We report on paleomagnetic directions gathered from 33 sites from (mostly Holocene) volcanics from Stromboli, loosely dated at present by few K/Ar and 14 C ages. In order to provide dating, the paleomagnetic directions were compared to the Holocene paleosecular variation of the geomagnetic field for the Mediterranean region, derived from direct geomagnetic observations and several archeomagnetic-paleomagnetic data sets. Petrochemical analyses from the paleomagnetic specimens revealed that each Holocene eruptive cycle of Stromboli was characterized by peculiar chemical characteristics. We suggest that before the 20th century AD paroxysms, powerful spatter-forming eruption(s) occurred during the 17th century AD, followed by three centuries of less energetic eruptions, when spattering was limited to the summit cones. A robust data set (4 sites, 52 samples) from the S. Bartolo flow, partially buried below the Stromboli village, constrains its age to 360 BC to 7 AD, in Greek-Roman times. The ca. 6200 years BP age inferred for a scoria exposed below a characteristic pyroclastic succession suggests its correlation with the Secche di Lazzaro pyroclastics, a major phreatomagmatic eruption occurring during the 6th millennium BP, synchronous with the major volcanotectonic collapse of the Sciara del Fuoco. Ages were provided for many lavas from the Neostromboli sequence (including the Labronzo, Nel Cannestrà, and Ginostra flows), indicating that huge effusive activity from lateral fissures fed by an evolving magma chamber occurred in the $6200-8000 years BP time window. The absence of volcanics with ages comprised between the 6th millennium BP and 400 BC implies a puzzling three-millennia ''eruption gap'' at Stromboli.

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[1] In the last years, paleomagnetism has been increasingly used to provide emplacement ages of loosely dated volcanics. Dating is achieved by comparison of paleomagnetic directions with a given reference curve of the paleosecular variation (PSV) of the geomagnetic field. Recently, a debate has developed on the achievable precision (the a 95 value) of the paleomagnetic directions and hence on the accuracy that ''paleomagnetic dating'' can yield. At 39 different sites from Etna we paleomagnetically investigated 13 flows (four ''test flows'' with known age, and nine loosely dated flows), emplaced between 122 B.C. and 1865 A.D. We systematically drilled 12 cores per flow spaced in three (far from each other) sites and demagnetized one specimen per core by alternating field cleaning. Results from the four test flows yield age windows effectively encompassing the respective true flow ages, when dating based on Bayesian statistics at a 95% confidence level is adopted. We find a 95 values for the flow mean directions ranging between 3.3°and 5.7°(4.5°on average), which translate into accuracies of age determinations of 136-661 years (307 years on average). Such dating uncertainty is likely underestimated, as we disregarded several kinds of errors that might affect both the fidelity of paleomagnetic recording and the PSV reference curve. The strong magnetization of both the underlying terrain and the cooling flow itself and mineral magnetic variations across the flows are the most likely sources for the scatter characterizing the recording process of the magnetic field in volcanic rocks.

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) 14 C 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.