Constraining age and volume of lava flow invasions of the Alcantara valley, Etna volcano (Italy). New insights from paleomagnetic dating and 3D magnetic modeling

摘要

The Alcantara River marks the northern border of Etna volcano, and along its NE sector, it forms a narrow NW-SE elongated valley that is carved in the Mts. Peloritani sedimentary sequences. The valley has been invaded by several lava flows during the growth of the main bulk of the stratovolcano edifice in the past 60 ky (Ellittico and Mongibello volcanoes). In this paper, we have constrained the age of the main lava flows forming the valley floor and reconstructed the length and volume of the main lava flow that impacted this area through a multidisciplinary approach integrating stratigraphic and aeromagnetic data analysis together with new paleomagnetic and C-14 dating. The new age determinations showed that the evolution of the present-day geological and hydro graphic setting of the valley was mainly conditioned by a few flank eruptions that occurred in the lower N flank of Etna during the activity of the Mongibello volcano. In particular, between 13.9 and 9.7 ka BP the valley floor was filled by the so-called Alcantara lava flow for its entire length up to the river mouth, reaching a maximum length of about 24 km. Later, two other flank eruptions - producing the so-called Mt. Dolce and Solicchiata lava flows - occurred at 9.1-7.2 and 7.3-7.2 ka BP (respectively), covering the eruptive fissure and the proximal portion of the Alcantara lava field and generated the most recent northward shift of the riverbed. Finally, 3D magnetic modeling allowed us to calculate the total on- and off-shore volume of the Alcantara lava flow as 1 km(3), a value comparable to those of the long-lasting historical eruptions of Etna. Conversely, the 24 km length reached by this lava flow is anomalously high when compared to lava flows of the past 15 ky, likely because its emplacement occurred within the valley floor, preventing any possibility of lateral expansion. (C) 2019 Elsevier B.V. All rights reserved.