Modern and recent sediment gravity flows offshore eastern Sicily, western Ionian Basin – Preliminary results from the MARGRAF project

Submarine sediment gravity flows are among the most important geological processes on earth. They drive the global sediment transport to the deep ocean and actively shape the continental slope and influence the development of sedimentary basins. These gravity driven flows also pose a hazard to offshore infrastructure and may contribute to tsunami generation. Despite their geological importance, sediment gravity flows are still not fully understood. The western Ionian Basin offshore eastern Sicily experiences high seismicity and host a considerable turbidite record. The 1908 Messina earthquake caused >60,000 casualties and generated a tsunami and an extensive turbidity current. The geohazard for this densely populated and economically important region in the central Mediterranean, however, remains poorly constrained. MARGRAF aims to improve the current understanding of submarine gravity flows on a regional and global basis using a multidisciplinary and multi-scale approach. Geophysical and sedimentological data interpretation, numerical modelling, and laser interferometry will be used to: 1) reconstruct the behaviour and evolution of the 1908 turbidity current; 2) evaluate the role of this turbidity current in the 1908 Messina tsunami; 3) test the effectiveness of using a submarine telecommunication cable to detect modern gravity flows; and 4) determine present day probability of new turbidity currents being generated along the eastern Sicilian margin. First results provide new information about the 1908 turbidity current behaviour. The main conduit for this gravity flow likely was the easternmost canyon-channel system of the western Ionian Basin, which extends from the Tyrrhenian Sea down to the accretionary wedge. High backscatter and the presence of numerous scours along its thalweg indicate recent sediment erosion and deposition. This canyon-channel system further extends to two of the three cable breaks recorded up to 18 hours after the earthquake on the Malta-Zante telecommunication cable. The presence of several sediment basins along this conduit indicates repeated sediment transport activity, while the numerous sediment failures that occur along the channel walls are interpreted as a result of flow undercutting. This canyon-channel system is connected to tributaries from both north-eastern Sicily and western Calabria, which are also characterised by high backscatter. In comparison, backscatter data from the eastern Sicilian margin south of Fiumefreddo Valley show that gravity flows are restricted to the tributary systems and do not travel long distances from the margin. The new results will be used to evaluate the role of the gravity flows for tsunamis. A potential impact of gravity flows on tsunami generation has been theorised by researchers studying submarine geohazards in the past, but needs yet to be tested. Addressing all objectives of MARGRAF has the potential to significantly improve the current understanding about submarine gravity flows.