Historical sea level changes and effects on the coasts of Sorrento Peninsula (Gulf of Naples): New constrains from recent geoarchaeological investigations

This paper describes the results of a multidisciplinary study of four geoarchaeological sites on the Sorrento Peninsula coast (Italy) where the submerged ruins of Roman buildings have enabled the ancient position of both the sea level and the coastline to be reconstructed. The results highlight that the sea level in Roman times, deduced from the submersion measurement of archaeological markers, did not exceed 1.2 m ± 0.30 m, except for Seiano whose submerged remains and surrounding area were heavily damaged by extreme events following the 79 CE Vesuvius eruption. The comparison of these results with the eustatic sea-level curve in Roman times together with the submersion of the tectonically stable site on the Tyrrhenian coast of Italy (Torre Astura, with a well-preserved Roman fishpond) demonstrate that the Sorrento Peninsula has been tectonically stable over the last two millennia. This behaviour started many thousands of years ago, not later than the last interglacial, while the nearby plain of Pompeii and probably the bottom of the adjacent Gulf of Naples have been subsiding at rates of 1 or more mm per year. In the same time span, two of the investigated coastal sectors (Capo di Sorrento and Punta Campanella) have not suffered any significant changes because their sea cliffs are cut in hard limestone. The tufa sea cliff of the Sorrento plain on the other hand, has been retreating by several metres. On the Marina di Equa (Seiano) alluvial coastal plain, which suffered the effects of the 79 CE eruption, the debris and hyperconcentrated flow produced a progradation of > 200 m, which has been totally dismantled over three centuries.