ABSTRACT 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 sam- ples, through high precision archeomagnetic dating checked by 226 Ra- 230 Th 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 We con- clude that i) historical documents alone are insufficient to recon- struct a coherent sequence of eruptions, and ii) a multidisciplinary approach is necessary to obtain a comprehensive eruptive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 protec- tion purposes, even for such a geologically recent period as that of the last 10 or 20 centuries. Thanks to these new archeomagnetic and 226 Ra- 230 Th 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. KEY WORDS: Etna volcano, archeomagnetic dating, 226 Ra- 230 Th dating, stratigraphy, historical account. INTRODUCTION The “historical period” of Mount Etna spans almost three millennia, and the popular belief is that eruptions of the Sicilian volcano during this period are well-known. This is not the case, however, because there are enormous gaps in the historical documents due to wars, barbarian invasions, and so on, or simply a lack of scientific interest (for instance, there are no valuable accounts from 252 AD to 1062, see TANGUY, 1981). Moreover, when going fur- ther backwards in time, historical accounts are often found to be unreliable and, above all, they are not precise enough to identify the eruptive vents or spatial extension of the lava flows. It thus follows that the size of eruptions and even a rough estimate of the volume of volcanic pro- ducts remain highly doubtful or unknown. Such data are crucial for reconstructing the dynamics of the volcano and for a statistical compilation of eruptions. High-preci- sion archeomagnetism, combined with radiometric dat- ing, has shown that 80% of the “historically dated” lava flows prior to the 1700s were not produced by eruptions quoted in the historical accounts, the discrepancies reaching centuries and sometimes a millennium (TANGUY et alii, 2003, 2007). Starting in the 1990’s, a new detailed geological survey was undertaken on Etna volcano by means of updated stratigraphic criteria (BRANCA et alii, 2004, 2008) with the aim of compiling the new geological map of Italy (SERVIZIO GEOLOGICO D’ITALIA, 2009a,b,c and d). Recently, these geological data were completed and updated (BELLOTTI et alii, 2010) in order to publish the new geological map of Etna volcano at 1:50.000 scale (BRANCA et alii, 2011a). The volcanic products related to the activity of the past 15 ka (Mongibello volcano) cover about 88% of Etna edifice (BRANCA et alii, 2011b; DE BENI et alii, 2011). During the making of the new geologi- cal map, several Holocene tephra marker beds were used to better constrain the age of the lava flows erupted in this time span. In particular, the reconstruction of the stratigraphic relationships between the lava flows and the pyroclastic fall deposit of the 122 BC plinian eruption (FG tephra layer of COLTELLI et alii, 1998, 2000) allows the identification of the lava flow fields of unknown ages erupted during the past 2,100 years. These new and updated stratigraphic data have thereby completed the historical record of Etna flank eruptions, in addition to the data derived from historical sources existing since the 1600s (BRANCA & DEL CARLO, 2005; TANGUY et alii, 2007). Indeed, the eruptions of the last 400 years (fig. 1) are well known both in terms of deposits and eruption year except for the lava flow named Dagala dell’Orso (BRANCA et alii, 2011a), located on the upper northwest slope (fig. 1a), belonging to an eruption not reported in historical sources. Conversely, the lava flows erupted before 1600 AD cannot generally be indicated by their eruption year, except in rare cases when accurate historical data are available. In particular, BRANCA et alii (2011a) have recog- nised 35 lava flows between the 122 BC plinian eruption and the 17 th century. Only 7 of these lava flows have been attributed to eruptions quoted in the historical sources, corresponding to the years 1566, 1537, 1536, 1446, 1408, 1329 and 1285. Such lava flows were identified through a critical examination of historical chronicles and checked by archeomagnetic data (TANGUY et alii, 2007). The 1285 (*) Institut de Physique du Globe de Paris and CNRS - 94107 Saint-Maur des Fossés cedex, France. (**) Université de Montpellier2 and CNRS - 34095 Montpellier cedex 5, France. (***) Istituto Nazionale di Geofisica e Vulcanologia, Osserva- torio Etneo, Piazza Roma, 2 - 95125 Catania, Italy. Corresponding authors: phone: +390957165800; e_mail: stefano.branca@ct.ingv.it (****) Dipartimento di Scienze Geologiche, Università di Catania, Corso Italia, 55 - 95129 Catania, Italy. New archeomagnetic and 226 Ra- 230 Th dating of recent lavas for the Geological map of Etna volcano JEAN-CLAUDE TANGUY (*), MICHEL CONDOMINES (**), STEFANO BRANCA (***), SANTO LA DELFA (****) & MAURO COLTELLI (***) Ital. J. Geosci. (Boll. Soc. Geol. It.), Vol. 131, No. 2 (2012), pp. 241-257, 8 figs., 4 tabs. (doi: 10.3301/IJG.2012.01) © Società Geologica Italiana, Roma 2012