Tephro-chronostratigraphy of the lacustrine interglacial record of Piànico, Italian Southern Alps: Identifying the volcanic sources using radiogenic isotopes and trace elements

Abstract: The chronostratigraphic position of the Piànico carbonate sequence, Oroebic Alps, Italy remains controversial, notwithstanding that it is one of the best-preserved records of an alpine interglacial. Two distal tephra were discovered in the sequence. The lowermost (t21d) is a rhyolitic tephra dated by K–Ar at 779±13ka, different from the uppermost phonolitic tephra (t32) with an assigned age of 393±12ka. The volcanic source of t32 was recently interpreted as being the Brown Leucitic Tuff of the Roccamonfina volcano, southern Italy. New trace element and Nd and Sr isotopic composition of t32 and of 420–200ka volcanic products of the Roccamonfina clearly indicate that this volcano is not the source of t32, but that it likely originated from the northern Roman Magmatic Province. The products of the initial explosive activity of Sabatini Mts., dated ca. 780–800ka, isotopically match t32 and are proposed as its source. This indicates that the previously inferred age of ∼400ka for t32 is erroneous. New isotopic and geochemical data of t21d confirm it as being associated with the first pyroclastic eruptions (790–710ka) of the Puy de Sancy volcano, French Massif Central. The Early-Middle Pleistocene K–Ar ages obtained previously for t21d, together with the isotopic attribution of volcanic sources to both tephra layers presented here, confirm Piànico as one of the best interglacial sequences of Cromerian age in the Western Alps. [Copyright &y& Elsevier]