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

During the Messinian Lago-Mare event, in the central Mediterranean area, co mpression- and extension-related basins developed as a consequence of the p ost-Tortonian evolution of the Tyrrhenian-Apeanines system. All these syn-t ectonic 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. Val entine 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 successi on of Mondragone 1 well, drilled in the Garigliano coastal plain, are locat ed in extension-related basins (hinterland or back-are basins). The recogni tion of ostracod assemblages with Paratethyan affinities allows them to be referred to the Messinian Lago-Mare event (Loxoconcha djaffarovi Zone). Thi s result allows us to consider the Tyrrhenian rifting, the accretion of the Apennine thrust belt and the increase in subsidence rate during thp flexur ation nf the foreland domain as synchronous processes due tn thp same geody namical process. Taking into account the thicknesses of the analysed sedimentary basins, dif ferent total subsidence rates have been computed for both the compression- and extension-related basins. The syn-rift basins that developed on the eas tern margin of the northern Tyrrhenian Basin (Volterra, Val di Fine and Tol fa-Blera Basins) recorded a mean total subsidence rate of 1,25 mm/a, wherea s higher subsidence rates affected the eastern margin of the central Tyrrhe nian Basin (5 mm/a, Garigliano coastal plain). The differences in horizonta l stretching and total subsidence rates that affected the Tyrrhenian extens ional area correspond to different migration rates of the Apennine orogenic system in the northern (10 mm/a) and central Apennines (40 mm/a). This dif ference in the total syn-rift subsidence rate fits in well with the segment ation 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. (C) 1999 Elsevier Science B.V. All rights reserved.