Sedimentological, mineralogical and geochemical characteristics of a Middle Pleistocene tephra layer in the lacustrine sediments from a long core in the Fucino Plain (Central Italy) [Caratteristiche sedimentologiche, mineralogiche e geochimiche di un livello tufitico del pleistocene medio nei sedimenti nella Piana del Fucino, Italia centrale]

This paper reports on the results of investigations carried out on a sandy tephra layer identified in a core taken in the central part of the Fucino Plain. The layer, mid-Pleistocene in age, is included in lacustrine sediments at a depth of approx. 100 m. Grain size data and macroscopic observations suggest an air-fall origin for the pyroclastic material. However, the presence of fauna remains in the same layer indicates that tephra underwent reworking by lake water. Microscopically, the tephra layer is mostly composed of scoria particles; clinopyroxenes, feldspars, biotite and leucite are also present The glass fraction has a foiditic-phonotephrit-tephriphonolitic chemical composition, also influenced by the phenocrysts contained in the scoriae. Data obtained do not support the hypothesis proposed by other Authors which indicates a local origin of tephra. Rather the new data indicate their provenance from the peri-Tyrrhenian volcanic districts, the activity of which was explosive during the Middle Pleistocene.