Coastal dynamics driven by physical and chemical processes: Costa Merlata near Brindisi (Southern Italy)

In the stretch of Southern coast of Torre Canne (Brindisi, South Italy), calcareous stone and calcarenites, which are the prevalent lithologies on the coast line, are replaced by sandy sediments. The degree of their cementation varies rhythmically in correspondence of the surface drainage channels (known as “lame”), which come with almost regular spacing from the hills of the hinterland and canalize also groundwater. This configuration of the surface and underground drainage lines determines the following conditions: (i) predominately saturated coastal sands in correspondence of the riverbeds and surroundings, (ii) a capillarity condition in the intermediate sections, (iii) evolving to unsaturated condition, with precipitation of carbonates and cementation of the coastal sand due to the evaporation and drying processes. The action of the sea in the area is constantly lifting in accordance with the known values of the post Würmian upward, and produces, in the previously configured situation, differential erosion of the coastline. As a result, the coastline is marked by rhythmic sequences of pocket beaches, interspersed with headlands of cemented and more resistant soils. The complete geomorphic process is well described in the various sections of the coast. In fact, the sea action continues in the narrow inlets and, as a further evolution, shapes the strips of land between the various “lame” initially into a hammer, while the last erosive attack phase of the sea is the complete separation of the hammer head by its handle, a process that takes place in a very long time and that leaves on the ancient coast line an array of small islets. The discovery of archaeological traces dating back to the Iron Age on one of these islets (the Apani reef) allow to estimate the time taken for the current coastal evolution, from Costa Merlata to the residual islets of the ancient coastline. The erosion process in place can be considered at present as a continuation of natural processes in the long period, controlled by both relative sea lift and particular hydrogeological and geochemical associated conditions. The differential erosion condition will presumably be subject to further acceleration as a result of the underway climate changes.