Vertical movements on the eastern margin of the Tyrrhenian extensional basin. New data from Mt. Bulgheria (Southern Apennines, Italy)

In this paper, we present the results of an integrated stratigraphical, geomorphological and morphotectonic study carried out in Mt. Bulgheria, a rocky headland located on the eastern margin of the Tyrrhenian extensional basin, in Southern Italy. Such a margin is characterised by the occurrence of uplifted headlands alternated with subsiding half-grabens. In particular, Mt. Bulgheria constitutes the northeastern margin of the Gulf of Policastro peri-Tyrrhenian depression. In the study area, Pliocene-Quaternary continental deposits and erosional landforms are present together with Pleistocene wave-cut and wave-built marine terraces. The integrated study of Pliocene-Pleistocene deposits and landforms allowed a detailed reconstruction of the geomorphological evolution of Mt. Bulgheria to be made. Furthermore, the tectonic behaviour of this portion of the Tyrrhenian margin during Plio-Quaternary times could be characterised. In particular, we recognised that a succession of alternated uplift and subsidence episodes affected the headland since the beginning of Early Pleistocene, when the eastward migrating coastline of the Tyrrhenian extensional basin reached MI. Bulgheria. The alternated uplift and subsidence events lasted for Early and Middle Pleistocene. Their cessation in Late Pleistocene is demonstrated by the occurrence of Late Pleistocene strandlines at an elevation comparable with that of the 130 ka sea-level highstand as recorded in stable areas of the Mediterranean region. The occurrence of marine terraces allowed the absolute vertical movements to be estimated. Their summation produced an uplift of the headland of 400 m since the beginning of the Santernian, 150 m of which occurred in the Middle Pleistocene. Along the onshore belt of the Tyrrhenian margin of Southern Apennines, other structural highs bordering the peri-Tyrrhenian depressions provide evidence for subsidence episodes interrupting the prevailing uplift trend recorded during the Quaternary. This, together with the distribution of Quaternary marine deposits (both downthrown and raised) and terraces, shows that the Tyrrhenian margin of Southern Apennines was affected by strongly variable vertical movements. (C) 1999 Elsevier Science B.V. All rights reserved.