Distribution, tephrostratigraphy and chronostratigraphy of the widespread eruptive products of Pavin Volcano

Abstract

A tephra erupted by Pavin volcano was found as millimetre- to centimetre-thick tephra beds in numerous peat-bogs and lake deposits of the Massif Central (France). At least two distinct Plinian pulses are attested by differences in chemical compositions of glass shards. A southern lobe was clearly delimited; it is widespread at least to Cantal (30 km from the volcano). At three northern localities as far as the Gour de Tazenat (50 km from the volcano), two populations of glass shards present in the tephra deposit indicate either overlapping of two compositionally-distinct lobes or a single lobe characterized by bimodal differences arising from magma mixing in the source volcano in the Chaîne des Puys. The Bayesian application, RenDateModel, to a sequence of radiocarbon and TL dates enabled us, at the 95 % confidence level, to constrain the age of Pavin eruption to 4720 ± 170 B.C., i.e. a current age of 6,730 ± 170 year, and to assess that between 100 and 700 years lapsed between the eruptions of Montcineyre and Pavin. Since Pavin Tephra was identified in sediments containing known pollen sequences pertaining to each lobe, the volcanic activity can be placed within the Atlantic palynozone between the spreading of Fraxinus and the synchronous palynozones of Abies and Fagus in that part of the Massif Central. The Pavin volcano generated the latest cataclysmic eruption of Plinian type in the Massif Central.