Untangling the complex origin of turbidite activity on the Calabrian Arc (Ionian Sea) over the last 60 ka

Abstract

The Ionian Sea, due to the presence of two accretionary prisms, the Calabrian Arc and the Mediterranean Ridge, associated with the subduction of the Nubia plate and the Eurasia plate, is the witness of large and catastrophic turbidite events. These events are associated with high magnitude earthquakes and tsunamis. They lead an important gravity-driven sedimentary deposit in the Ionian basin. In this study, we analysed turbidite deposits in order to establish a calendar of the palaeoseismicity and volcaniclastic events from Etna on the Calabrian Arc. Two gravity cores collected in a slope basin on the Calabrian Arc and in the Ionian abyssal plain record more than two hundred turbidites over the last 60,000years. These turbidites were dated with a multi-proxy approach: radiometric dating, tephrochronology and sapropels. The origin of the turbidites was studied with a sedimentary approach: grain-size, lithology, thin section, and geochemistry of volcanic glass. The results suggest that three triggers are responsible for the deposits of turbidites. There are siliciclastic turbidites triggered by earthquakes and tsunamis waves, and volcaniclastic turbidites triggered by the Etna volcano eruptions or flank collapses. Co-seismic turbidites present different recurrence times depending on the location of the core. On the Calabrian Arc, recurrence times vary between 450 and 1000years according to the periods in time. On the abyssal plain, recurrence times are shorter and more regular: around every 240years.