Middle to late Pleistocene coastal deposits of Alghero, northwest Sardinia (Italy): Chronology and evolution

Abstract: The shallow-marine to coastal deposits of Alghero have been dated using the Optically Stimulated Luminescence (OSL) method, and studied to define the palaeoenvironmental evolution of coastal areas in northwest Sardinia. Dating, coupled with sedimentological and stratigraphical analyses, allowed the subdivision of the succession in four unconformity-bounded units (U2, U3a, U3b, U4). Unit U2 of penultimate glacial stage (MIS 6; ca. 150ka) is composed of dune deposits formed intermittently along rocky coastal areas under strong wind conditions. Subunit U3a is composed of cliff-bounded gravelly dominated pocket beach deposits, commonly highly fossiliferous, and is assigned to the interglacial MIS 5e (ca. 125ka). Subunit U3b is characterized by sandy beach to coastal systems of the isotopic sub-stage MIS 5c (ca. 100ka). The unconformity between U3b and U4 marks the initiation of last glacial regression (MIS 5a/4; ca. 77ka) during which shelf areas were exposed and small incised valleys developed. Along the valley flanks, colluvial or sheetflood sediments were deposited and, in the central part thick reddish paleosols formed. Valleys were eventually filled by thick aeolian dune deposits (MIS 4–3) indicating persistent inland sand transport. Around Alghero, coastal carbonate-rich dunes preferentially formed and migrated inland during lowstand and falling stages when the climate is relatively cold, vegetation is quite open, winds are fairly strong and sediment supply from exposed shelf areas is high. [Copyright &y& Elsevier]