Coastal towers and historical sea level change along the Salento coast (southern Apulia, Italy)

The perimeter of Salento Peninsula (southern Apulia, Italy) is studded by numerous coastal towers built in the XVI century aiming to create an “early warning system” against pirates' attacks. At present, two of them, Fiumicelli tower on the Adriatic coast and Pali tower on the Ionian one, have bases a few decimeters below mean sea level. The unusual position of both coastal towers can be explained by taking into account geomorphological features of the coastal area and the relative sea level change during the last 500 years.Geomorphological analysis reveals the occurrence directly in front of the two coastal towers of a wide rocky shore platform to about 1 m depth. If a mean sea level about 0.6–1.0 m below present position is supposed at the time of coastal tower construction, the wide shore platform would be slightly above sea level and would be able to protect the towers from sea storms. Furthermore, by comparing these data with the results of available glacio-hydro-isostatic models for southern Apulia during the late Holocene, it is possible to postulate tectonic subsidence of the Salento coastal area during the last five centuries.The collated data establish the Quaternary tectonic history of Salento Peninsula. It experienced a period of general subsidence during the Lower Pleistocene that was interrupted by rapid uplift during the Middle Pleistocene. Uplift stopped at MIS 9.3 (about 330 ka), replaced by a phase of substantial stability which lasted until the Late Pleistocene–Holocene. Finally, active tectonic subsidence has affected the coast of Salento peninsula during the last four millennia probably in response to the recent doming of the region.