Morfologie costiere e depositi quaternari tra Agropoli e Ogliastro Marina (Cilento - Italia Meridionale)

Abstract

The studied area developing between the towns of Agropoli and Ogliastro Marina is part of a wide promontory closing the Gulf of Salerno to the south (province of Naples, southern Italy). The promontory is made up of sandstones and marls belonging to the "Cilento flysch" formations. The coast is characterised by small bays (Trentova, Santa Maria and San Marco bays), separated from one another by rocky promontories (Tresino and Licosa Capes). A detailed geological survey of the Quaternary marine, transitional and continental formations in the bays was carried out, together with the analysis of associated coastal forms (depositional and wave-cut terraces, notches, etc.). Terraced inner portions of the coastal plain behind the Santa Maria bay, are made of a transgressive-regressive succession (Comenale complex) with (upward) lagoon clay, fossiliferous sand of marine environment and eolian sand. This complex is present up to 45 m a.s.l. and represents the oldest depositional event in the bay. It is covered by the Sant'Antonio transgressive complex, which is made up of a fossiliferous beach rock overlaid by loose eolian sands. This latter complex outcrops up to 20 m a.s.l. and is cut by three orders of wave-cut terraces (at 8-10, 3 and 1.5 m a.s.l., respectively). In the San Marco bay, a sandstone formation outcrops; it shows many sedimentary structures and can be ascribed to an upper shoreface environment. Sandstone overlays a palseosol outcropping at the altitude of 50 m a.s.l., which evolved above eolian sands; both are cut by two orders of wave-cut terraces located at 10 and 4 m a.s.l., respectively. In the area of Licosa Cape, 4 orders of well-preserved wave-cut terraces are present, at 20÷25; 8÷10; 4 and 1.5 m a.s.l., respectively. A thin cover of either sandy or biogenic deposits was found locally in association with these terraces. In conclusion, five ancient sea-level stands are identified in the promontory area at elevations ranging from 1.5 to 50 m a.s.l. The oldest levels are represented by two eolian and marine sedimentary successions (Comenale Complex and sandstones of the San Marco-Sant'Antonio Complex 50 and 25 m a.s.l., respectively ), separated by a major regression. The Comenale complex refers to a sea highstand older than the Last Interglacial, as indicated by lithic artifacts. The San Marco-Sant'Antonio complex seems to be older than last Interglacial, as well. Both complexes have been tentatively ascribed to isotopie stages 9 and 7. The various peaks of the Last Interglacial (isotopie stages 5e and 5c), are represented by lowest abrasion terraces (8÷10 and 4 m a.s.l.) that cut both the pre-Quaternary substratum and the San Marco-Sant'Antonio complex. The age of the youngest platform (at 1.5 m a.s.l.) is uncertain and may represent either a Last Interglacial positive peak (isotopie stage 5a) or the maximum peak of the post-glacial transgression (Versilian transgression, isotopie stage 1). The study also shows that the area was affected by tectonic movements between stages 7 and 5 and between sub-stages 5e and 5c.