Elementi geomorfologici e geoarcheologici per la valutazione dei moti verticali recenti del paesaggio costiero della Campania / Geomorphological and geoarchaeological indicators of vertical ground motions to reconstruct landscape morphoevolution of Campania

Geoarchaeological and geomorphic surveys in progress along the submerged coastland of Campania are contributing to evaluate type, entity and rate of ground vertical movements responsible of archaeological heritage submersion, as well as of littoral erosion. Discrimination of vertical motions linked to bradyseismic, tectonic, volcano-tectonic and subsidence phenomena, sometimes mutually interacting each other, play a key role to understanding coastal morphoevolutionary dynamics since the last 3000 years. The ancient sea levels registered along the regional waterscapes show geomorphologic elements related to their settlement phases during the Holocene. Palaeo shorelines are often located at different depths, so they supply information about sea-level changes due to tectonic-eustatism and volcano-tectonic interactions. The study of archaeological structures, currently at depth not compatible with the sea level of their age, allows to deduce both palaeo sea-level traces and ground vertical deformations in the analyzed case studies. In particular, different sectors of the Gulf of Naples were surveyed, among which (i) the Gulf of Gaeta (Torregaveta and Sinuessa), (ii) the Neapolitan-Phlegrean Fields area (Cape Miseno-Castel dell’Ovo), (iii) the Phlegrean Islands (Procida, Vivara and Ischia), (iv) the Vesuvius coast (Portici-Castellammare di Stabia), and finally (v) the Sorrento Peninsula and Island of Capri. Results highlight differential vertical movements mainly linked to tectonic (i), volcano-tectonics (iii-iv) bradyseismic, (ii) complex vertical motions (bradyseism, subsidence, tectonics and volcano-tectonics interplay), and (5) coseismic or landsliding displacement. The highest values registered (i.e., -4.3 m along the Vesuvius coast, -4.5/-12 m along the Neapolitan-Phlegrean Fields coast, -3.5/-7 m at Torregaveta-Sinuessa, -9/-4.5 m in the islands of Vivara and Ischia, respectively), and recently -4.2 m in the Island of Capri, vary in the different morphostructural sectors of the gulfs of Naples and Gaeta, resulting higher than 0.2 mm/y which represents the average subsidence rate during the last 125 kyr. Among the case studies, the underwater survey of Sinuessa was particularly interesting: actually, it was possible to reconstruct the coastline morphoevolution phases through the identification of submerged geoarchaeological markers as a millstone carved into the Campanian Ignimbrite, 24 Roman pilae and the ruin of a stone-paved road. The highest value of ground vertical downlift (-7 m) likely indicates recent tectonic activity. The rise in sea level is not homogeneous throughout the Gulf of Naples due to different bradyseismic entity. Therefore, the relative downlift of Miseno, Bacoli, Baia and Gaiola are different, with maximum subsidence rate between Secca delle Fumose and Island of Nisida. The Sorrento Peninsula is relatively stable and the sea-level rise can be attributed only to the glaciohydro-isostatic post-glacial component. In the carbonate Island of Capri, the Roman ruins of a Tiberius’ villa maritima lies down to -4.20 m depth. Even considering the sea level during Roman age (-1.25 m lower than the present-day), the downlift is incongruent with the general island uplift of ~1.5 m due to tectonics, marked along the cliffs by the current elevation of the palaeo-sea notch modeled at 5.5 m ~125 kyr BP (MIS 5.5 high stand, Tyrrhenian). Therefore, a rapid displacement due to coseismic or landslide phenomena during post-Roman age occurred. The analysis of the ports of the island of Crete highlights the presence of typical architectural features of port of the Phlegrean area, therefore the geoarchaeological markers can be considered valid for the all Mediterranean Sea. The validity of these geoarchaeological markers was supported by the minero-petrographic analysis of the Greek ports. The analysis highlighted the use of the same mix design to the Greek and the Phlegrean ports, as proof of the rigid manufacturing criteria used by the Romans. Finally, the systematic study of the coastal ruins of Campania has improved the knowledge of the geoarchaeological markers for the reconstruction of the ancient sea levels, introducing new parameters related to the geomorphological and the morphoclimatic features.