The Remote Sensing-Stratigraphic Approach Applied to the Reconstruction of Holocene Sedimentary Evolution in Coastal Areas: Case Studies from Arno and Po Delta Plains (Italy)

The growing availability of open-access databases, made the RS data and analyses to be increasingly employed in several geological research areas, including Quaternary and Environmental Geology. Despite the frequent use of the RS in alluvial-coastal plains paleohydrographic reconstruction, especially to identify stagnant versus well-drained areas (i.e., past wetlands and paleochannels, respectively) by means of brightness contrasts on images, the relationship between surface RS-derived traces and shallow subsurface stratigraphy remains underexplored. The present PhD thesis represents a contribution to this open issue, through the application of a multidisciplinary approach integrating RS (optical multi/hyperspectral images and DTM LiDAR) with sedimentologic and stratigraphic field data in the study of the Holocene evolution of paleodrainages from two coastal-deltaic areas: San Rossore site (SR-Arno plain) and Mezzano Valley (MV-Po plain). The analyses of 27 scenes from Landsat, ASTER, Sentinel2a and Hyperion allowed to identify paleochannels traces in the two sites. Field surveys and soil sampling campaigns performed on selected traces to define their surface sedimentological and optical characteristics, invariabily highlighted silty-clayey composition. A cross-reference was performed between traces and the shallow subsurface (i.e., uppermost 10 m) through the collection of 26 auger and continuous core data on which facies analysis, 14C dating and stratigraphic correlations were performed that allow to identify buried (2-4m bgl) channels. Their surface visibility, connected to the soil moisture distribution, resulted to be influenced mainly by the distribution of organic-rich deposits and/or by the shallow subsurface stratigraphic architecture. The “stratigraphic calibrations” extendended along RS-detected traces suggested that during the early highstand (6000-3000 yr cal BP) the MV experienced a tidally-influenced lagoon phase with the development of 2 networks of “tidal-channels”, whose formation was favored by local factors (suh as low topographic gradient and continuous beachridges development) while, the Pisa lagoon, in the same time-interval, was gradually filled by distributary channels.