New findings of Late Glacial Etna pumice fall deposits in NE Sicily and implications for distal tephra correlations in the Mediterranean area

Abstract

Pumice fall deposits found in the Nebrodi Mountains and along the Alcantara River, close to the town of Randazzo (NE Sicily), have been studied to derive information about their volcanic source and age. The geochemical Na-alkaline affinity of juvenile products, benmoreite to trachyte, clearly indicates they originated from Etna volcano (Sicily). Major (EMPA) and trace (LA-ICP-MS) element compositional data on matrix glasses indicate that the investigated deposits have a compositional affinity consistent with the tephra deposits of unit D produced by the Ellittico calderaforming eruptions between ca. 17 and 19 cal ka BP. Furthermore, their compositions correspond to the distal tephra equivalent found in some lacustrine and marine cores in Central Italy (Y-1, TM-11), Tyrrhenian Sea (Et-1; MD10α) and Adriatic Sea (Pal94-66-358; Pal94-8-353). We applied the principal components analysis (PCA), a statistical tool able to reduce the variability of a complex system, to compare the compositions of the proximal samples with the possible distal counterparts found in drill cores of the Mediterranean area. On the basis of northward dispersal of the studied deposits and their geochemical features, we suggest they represent a previously unreported sub-Plinian/Plinian eruption of Ellittico volcano producing medial-distal pumice fall deposits in the Nebrodi Mountains and close to Randazzo, named here the D1c layer. The discovery of these deposits helps solve the problem of distal correlations of the northerly dispersed tephra from Etna related to unit D, for which no definitive attribution with proximal units was given in previous studies. The results presented here add to the knowledge of the eruptive history of the volcano and contribute to expanding the proximal geochemical glass dataset for distal tephra correlation in the Mediterranean region during the Late Glacial period.