Facies analysis of the Late Quaternary deposits along the coast between Livorno and Piombino: paleoenvironmental and neotectonic implications

The coast between Livorno and Piombino (Southern Tuscany) displays geological evidences of quaternary tectono-eustatic interaction. Through an accurate review of previous works and a detailed geological survey, 116 sites where outcrop Late Pleistocene deposits have been located. Facies analysis allowed the identification of 11 different lithostratigraphic units, constituting a larger number than the 3 or 4 units recognized in previous studies (Cortemiglia et al., 1983; Hearty & Dai Pra, 1987; Costantini et al., 1993 and Mauz, 1999).They are constituted by mainly sandstone levels formed in upper shoreface to foreshore/backshore and coastal dune environments, separated by silty and sandy pedogenized continental deposits. In particular, aeolian deposits have been documented in this area, on the basis of sedimentological features (e.g. presence of contorted bedding, pin stripe laminae, convex-upward stratification) and fossiliferous evidences (oligotipycal non-marine mollusc fauna, Caprid track-ways). A stratigraphical correlation sketches, based on recent chronostratigraphic data (Hearty & Dai Pra, 1987; Mauz, 1999), have been proposed for the study area and, compared with the last 130 ky global sea-level curves, suggest a tectono-eustatic interaction. The superposition of the 11 lithostratigraphic units laid between MIS5 and Holocene (MIS1), associated with their depositional environment interpretation, implies repeated phases of subsidence followed by a very recent uplift. Coastal sectors with differential subsidence/uplift rates have also been recognized along the study area. These data are in strong conflict with other neotectonic reconstructions, based on MIS 5.5 markers (Nisi et al., 2003; Ferranti et al., 2006), which suggest stability or gentle uplift for this area.