Holocene onshore/offshore tephra correlation of Mt. Etna, Sicily

Abstract

The volcanic history of Mt. Etna is mainly known from studies of subaerial deposits and stratigraphy. However, little is known about the offshore deposits, which can provide a more detailed insight into geological and sedimentological processes affecting the flanks of Mt. Etna. During RV Meteor Cruise M178, eight gravity cores were taken offshore across the continental margin east of the volcanic edifice to re-evaluate the volcanic history of pre-historic eruptions and mass wasting events in the area. In total, we investigated 87 marine tephra layers in order to build a marine tephrostratigraphic framework. Based on major element compositions of glass shards, sediment componentry, and petrographic characteristics, 27 layers were identified as primary pyroclastic flow and fall deposits, i.e., directly related to an explosive volcanic eruption. However, most of the remaining tephra layers are interpreted to represent deposits of secondary density currents and are not necessarily related to a volcanic eruption. The marine dataset is complemented by twelve onshore samples taken from major explosive eruptions. Applying geochemical fingerprinting of volcanic glass shard compositions, we correlated eleven marine tephra deposits to seven well-known Mt. Etna eruptions (FV, FF, FG, FL, FS, TV, and M1 eruptions) within the last 12 kyr, which provide valuable time markers in the marine sediment record. Furthermore, we correlated ten marine tephra layers between the marine cores (four individual eruptions) and identified another six primary layers in single cores. In total, we discovered 17 widespread volcanic events in the marine record, including four previously unknown eruptions between 10 and 7.7 ka, which indicate that Mt. Etna was more active than previously thought during this time period.