Nuovi dati sul pleistocene di Valle Ricca (Monterotondo, Roma)

Abstract

Massive grey clays followed by more or less compact sandy clay and yellow sand crop out along the southern bank of the Valle Ricca creek, on the NE of Rome. A very distinctive ash level near the base of the section exposed in Tini and DCB quarries is offset by small scale normal faults. Previous studies assigned various chronostratigraphic positions to the succession: (1) Late Pliocene close to the Pleistocene boundary (Carboni & Conti, 1977); (2) Plio/Pleistocene, whose boundary has been recognized near the ash level, is referred to the Réunion subchron and dated 21 Ma (Arias et al., 1980); (3) Late Pliocene (Arias et al., 1990). In this paper, the Bulimina marginata and Bulimina elegans marginata zones are identified, the latter containing the first known occurrences of Globigerina aff. calida calida, G. calabra and Bulimina etnea. Therefore, the Plio/Pleistocene boundary is identified there by the FO of G. aff. calida calida and G. calabra, in agreement with the P/Q boundary stratotype of Vrica (Aguirre & Pasini, 1985).