The palaeogeographic setting and the local environmental impact of the 130 ka Falconiera tuff-cone eruption (Ustica island, Italy)

Abstract

This research focuses on the effects of the last eruption occurred at Ustica, which formed the Falconiera tuff-cone at around 130 ka BP in the north-eastern tip of the island. This eruption was mainly explosive and phreatomagmatic, with the emplacement of a series of pyroclastic-surge beds that determined the formation of an asymmetric tuff cone. This is the most easily recognizable Ustica volcanic edifice, although its north-eastern sector has been partially dismantled by the erosion. A section of the feeding conduit is exposed northward, showing the solidified lavas that fed the latest stages of the eruption. These were characterized by the formation of an intracrateric lava lake and a Strombolian scoria-fallout deposit.

The eruption occurred during the Upper Pleistocene Marine Isotopic Substage 5.5, a warm period characterized by a high sea-level stand (6±3 m above the present sea level in stable areas) and the diffusion in the Mediterranean sea of subtropical flora and fauna. This eruption slightly modified the Ustica morphology, but impacted on both marine and terrestrial environments, burying beach deposits rich of mollusk shells (i.e. Strombus bubonius, Conus testudinarius, Brachidontes puniceus), colonies of corals (Cladocora caespitosa) and subaerial plants (Chamaerops humilis). These organisms, found in some cases in their vital position, along with other lines of evidence, give information on the palaeogeography of this sector of the island at the time of the eruption, and on the local impact of this event on the environment.