Extension- and compression-related basins in central Italy during the Messinian Lago- Mare event

Abstract

During the Messinian Lago- Mare event, in the central Mediterranean area, compression- and extension-related basins developed as a consequence of the post-Tortonian evolution of the Tyrrhenian–Apennines system. All these syn-tectonic sedimentary basins were characterized by different subsidence rates and sedimentary processes. Several sections located in different tectonic domains from the Tyrrhenian to the Adriatic margin of the Apennine chain have been investigated: S. Valentino in Abruzzo Citeriore, Roccamorice, Penscosansonesco–Roccacaramanico and Le Vicenne sections are located in compression-related basins (foreland basin system), while the Tolfa–Blera sections and the sedimentary succession of Mondragone 1 well, drilled in the Garigliano coastal plain, are located in extension-related basins (hinterland or back-arc basins). The recognition of ostracod assemblages with Paratethyan affinities allows them to be referred to the Messinian Lago- Mare event ( Loxoconcha djaffarovi Zone). This result allows us to consider the Tyrrhenian rifting, the accretion of the Apennine thrust belt and the increase in subsidence rate during the flexuration of the foreland domain as synchronous processes due to the same geodynamical process. Taking into account the thicknesses of the analysed sedimentary basins, different total subsidence rates have been computed for both the compression- and extension-related basins. The syn-rift basins that developed on the eastern margin of the northern Tyrrhenian Basin (Volterra, Val di Fine and Tolfa-Blera Basins) recorded a mean total subsidence rate of 1.25 mm/a, whereas higher subsidence rates affected the eastern margin of the central Tyrrhenian Basin (5 mm/a, Garigliano coastal plain). The differences in horizontal stretching and total subsidence rates that affected the Tyrrhenian extensional area correspond to different migration rates of the Apennine orogenic system in the northern (10 mm/a) and central Apennines (40 mm/a). This difference in the total syn-rift subsidence rate fits in well with the segmentation model of the Tyrrhenian–Apennines system along a NNE–SSW lithosphere discontinuity, which crosses the system from Ancona (northern Apennines) to the R. Selli lineament, in the Tyrrhenian Basin.