MAGNETIC STRATIGRAPHY OF ETNA PRODUCTS. I - MEDIEVAL LAVAS

Mean magnetisation directions from 6 lava flows of questionable historical age have been determined The results, which are based upon very stringent linearity criteria during demagnetisation, point out erroneous dating and the corresponding lavas can be ascribed to medieval activity of Mount Etna, as already suggested for some of the investigated flows, covering a time interval of some centuries around AD 1000. The site mean direction of AD 1536 historically dated lava flow agrees with a previous study (Tanguy et al., 1985), while the site mean directions of AD 1566 and AD 1169/812 differ significantly from those reported earlier. Neither AD 812 nor AD 1169 dating is consistent with the site mean direction of the related flow being compatible with an emplacement age possibly a few decades before AD 1000. The 3 lava flows historically dated AD 1595 exhibit different within site mean directions indicating that they cannot be referred to coeval activity of the volcano; the site mean direction of one of the flows is compatible with an emplacement occurring very close to AD 1000. The resulting SVC is significantly shifted eastwards with respect to that of previous study (Tanguy et al., 1985). However, its older part nearly overlaps the medieval Vesuvius SVC relocated to Etna. This indicates that the strict linearity analysis carried out during demagnetisation has allowed to clearly define the characteristic magnetisations of the investigated lava flows. The adopted procedure is appropriate for performing successful magnetic stratigraphy surveys in volcanic areas.