A multidisciplinary study of the volcanoclastic deposit named “Chiancone”, inland and offshore, in the frame of the evolution of volcanism in the Etna area

In this work a detailed study about the volcanoclastic deposit pyroclastic cone called Chiancone is carried out by 98 Vertical Electrical Soundings (VESs) and by analysis of the surface morphology made by two Digital Elevation Model (DEM) with high resolution. The results seem to confirm what has been suggested by other researchers and shed some light on some dark aspects of this volcanoclastic deposit. In particular it was found that the Chiancone is quite a complex geologic formation, whose deposition took place in several steps, filling in depressions of various conductive substrate to depths of at least 300 m below the sea level. The conductive substrate generally shows a higher resistivity than a clay one and is strongly tectonized and eroded. The multibeam surveys carried out offshore in the Ionian Sea, allow us to identify the geolithological nature of the substrate, never before detected in the past. They show the existence of an outcrop of a large cone-shaped submarine pyroclastic body, about 600 m deep, covered, near the coast, by Chiancone deposits. The authors believe therefore that this pyroclastic body may form “inland” the conductive substrate of the formations outcropping in the studied area (lava and Chiancone) and representing the product of the demolition of one or more existing volcanic apparatuses prior to the Trifoglietto and Mongibello, which was given, in the past, the name of Ancient Etna.

► On the basis of our considerations, various conclusions can be drawn.
► In the CH’s pyroclasts there are various lithological facies which were generated 50–40 ky B.P.
► In various phases, the CH’s volcaniclasts have occupied some Grabens of the pyroclastic body C.
► The CH’s pyroclasts poured into the sea reaching a maximum depth of 100 m b.s.l. near Torre Archirafi, overcoming two morpho-tectonic steps.