New archeomagnetic and 226Ra-230Th dating of recent lavas for the Geological map of Etna volcano

This work deals with the dating of Mount Etna lava flows and
eruptive fissure deposits to the last four millennia following field
investigations and stratigraphic data (BRANCA et alii, 2011a). We
have studied 24 of these volcanic products, including 301 large samples,
through high precision archeomagnetic dating checked by
226Ra-230Th radiochronology, thus providing additional material to
the previous paper by TANGUY et alii (2007). In most cases our
results allow attributing ages to the historical period, although two
flows are shown to be prehistoric. For the historic lavas, archeoma -
gnetic ages can be defined within decades, except for three of them
that erupted during a time span (Greco-Roman epoch) when the
geomagnetic field underwent little variation. Although 60% of these
volcanics exhibit ages comprised between 700 AD and 1850, only
one (1285) is mentioned by contemporary written accounts. We conclude
that i) historical documents alone are insufficient to reconstruct
a coherent sequence of eruptions, and ii) a multidisciplinary
approach is necessary to obtain a comprehensive eruptive history of
such a very active volcano, useful for both scientific and civil protection
purposes, even for such a geologically recent period as that of
the last 10 or 20 centuries. Thanks to these new archeomagnetic and
226Ra-230Th data coupled with stratigraphic data, a comprehensive
volcanic history of the still-outcropping Mount Etna volcanics is
now available for the last 2,400 years.