Bio- and magneto-stratigraphy in the Tiber valley revised

The stratigraphy of three sections of marine deposits in the Tiber valley, north of Rome, was investigated in detail. Biostratigraphic investigation covered the Valle Ricca (Tini quarry), Fosso Liano and Lugnano sections. The Valle Ricca and Lugnano sections show continuity in sedimentation from the latest Pliocene to Early Pleistocene. In the Fosso Liano section Upper Pliocene sediments are missing, as in other outcrops in central Italy, and the Lower Pleistocene deposits lie unconformably on the Middle Pliocene ones. Possible causes of these features are discussed. Magnetostratigraphy and rock magnetism analyses were performed only in the Valle Ricca section. The data shows that the previously recognised reversal around a volcanic level is the effect of strong changes in the magnetic mineralogy and it is not representative of true geomagnetic changes. (C) 1998 INQUA/Elsevier Science Ltd. All rights reserved.