Palaeomagnetic dating of the Neostromboli succession

Abstract

The Neostromboli volcanic succession is characterized by packages of lava flow units and scoria beds erupted from the summit of the Stromboli volcano, and by scoria cones and lava flows poured out from lateral vents and fissures. Available radiometric ages constrain Neostromboli activity in the 14–4 ka BP age window, but the chronological relations of central vs. peripheral activity are still poorly understood. Furthermore, radiometric and palaeomagnetic ages for some of the peripheral eruptions are strikingly inconsistent. Here we report on the palaeomagnetic dating of thirty-four sites from Neostromboli products. Seventeen are new palaeomagnetic directions, while additional seventeen ages are recalculated - using published directions by Speranza et al. (2008) - with the recent SHA.DIF.14K palaeo-secular variation (PSV) field model. We show that the beginning of Neostromboli succession could be much younger than the commonly accepted ≈14 ka onset, providing our oldest data an age of ≈9 ka. The improved geochronological resolution allowed by palaeomagnetic dating sug- gests that the early stages of the Neostromboli activity occurred at 9–8 ka BP and were characterized by summit lava flow units blanketing both the SW and northern volcano flanks; after ≈7.5 ka lateral eruptions from periph- eral cones and fissures became dominant. We suggest that the intense flank activity enabled magma-water inter- action thus yielding explosive activity and repeated collapse events, leading to the Sciara del Fuoco formation. Our work confirms that PSV analysis of Holocene volcanics may yield eruption chronology definition with an ac- curacy unlikely to be achieved with other radiometric techniques.