Evidence of Marine Isotope Stage 5.5 highstand in Liguria (Italy) and its tectonic significance

摘要

The Quaternary shoreline displacements in Liguria are still poorly known. This paper completely revises and reinterprets the literature on this topic, taking into account only those markers that allow precise estimates of altitude and age of sea-level highstands. Among the sites showing geomorphological evidence of MIS 5.5 present in Liguria, three were considered reliable. In Eastern Liguria a beach deposit, with a terrace inner margin at 28 m a.s.l (Villa Monteverde), was dated by OSL. In Western Liguria, in a site close to the French border (Balzi Rossi), a notch present inside two caves indicating a sea-level altitude of 12 m is associated with a deposit containing a faunal assemblage with Strombus bubonius. This gastropod appeared in the Italian Seas only during the last interglacial highstand, and provides a unique marker of the MIS 5.5 horizon. Eastward, near Imperia, another site (Madonna dell'Arma) shows similar evidence, but in this case, the notch is not preserved because the cave is carved in a very soft Oligocene conglomerate. Late Quaternary tectonic movements along the different tracts of the Ligurian coast seem to have occurred apparently with different, although rather low, uplift rates. The connection between the Alpine and Apennine chains (Sestri-Voltaggio line) divides the Ligurian arch into two parts. The Alpine sector can be considered stable, whereas the Apennine relief displays in its central part an uplift rate of 0.16 mm/yr.