Giulio Bigazzi, Giovanni Zanchetta, Francesco Paolo Bonadonna, Gabriello Leone; Nuovi dati cronologici sui depositi cineritici del Valdarno inferiore (Toscana). Italian Journal of Geosciences ; 119 (1): 121–124. doi:
Two new ages were determined using the fission-track method on apatite grains separated from a volcanic ash level that was recognised in sedimentary series from the lower Arno valley (Tuscany, Italy). The samples were collected from the series located at Poggio al Vento and at Cava Campani (Pontedera), along the left bank of the Arno River. These new ages, around 0.5 Ma, agree within the experimental errors with those previously determined on glass of the same unit. However, they have to be preferred for their better precision and potential better accuracy. The S. Romano Unit, which contains the studied tephra, has been assigned to the isotopic stage 13.