A paleosol has been identified in an area of great natural interest for its geomorphologic and naturalistic aspects between the municipalities of Bagnoregio and Castiglione in Teverina (Viterbo, Italy). This investigation represents the preliminary steps of a study aimed to know the specific environmental features and dynamics prior to the eruptions of the "nenfri" of the Paleovulsini complex. The physico-chemical characteristics and some horizons morphological details such as the presence of roots fingerprint, the polyhedric angular and columnar structure suggest incipient weathering and paedogenesis. Moreover, the presence of nodules and the high salinity of deep horizons suggest the incorporation of pyroclastic material into a hydromorphic environment at the time of the eruptions, putting forward the hypothesis of a paleo-marsh under an arid paleoclimate
