New chronostratigraphic constraints for the eruptive history of Alicudi volcano (Aeolian archipelago, Italy)

By adopting an unconformity-bounded stratigraphic approach, raised terraced marine deposits developed during marine isotope stages (MIS) 5c-5a (100-81 ka) provide new insights into the late Quaternary eruptive history of Alicudi volcano (Aeolian archipelago, southern Italy). Given the occurrence of widespread Brown Tuffs tephra-layers (<70 ka) from Vulcano Island, marine deposits allow identification of the inter-island-scale allogenic unconformities UII, UI and L3, driven by sea-level fluctuations. These unconformities make possible effective correlation of the volcanic succession of Alicudi with the stratigraphic sequences of volcanic rocks on the other islands of the Aeolian archipelago. Combined with four autogenic unconformities of volcanic and volcano-tectonic origin (A1, A2, A3, aa), the allogenic unconformities are regarded as a tool for reconstructing the geological evolution of Alicudi volcano, as the result of the interaction between local and external volcanism, volcano-tectonic processes and sea-level oscillations. Refined morphostratigraphy between marine deposits and volcanic products, combined with re-examination of available radiometric ages, indicates that a large part of volcano development occurred in the course of the last interglacial (=MIS 5), between 120-110 ka (age of the oldest exposed volcanic rocks) and 110-81 ka. Over this period of time, volcanism was characterized by constant localisation of eruptive vents in the summit area, homogeneous effusive to strombolian explosive eruptive style and progressive slight chemical differentiation of the erupted products (from CA basalts to andesites). The eruptive history of Alicudi was repeatedly interrupted by prolonged periods of dormancy and three distinct and successive episodes of volcano-tectonic collapse of the summit volcano. The most recent volcanic activity occurred in the late Pleistocene (~41-26 ka), with the emplacement of high-K CA endogenous lava domes, filling the morphologic depression related to the latest summit collapse, and of several lava flows descending the south-eastern flanks of Alicudi volcano.