La valle villafranchiana della Tùrrite di Gallicano (Val di Serchio) e le sue implicazioni neotettoniche

The villafranchian valley of Tùrrite di Gallicano (Serchio Valley) and its neotectonic implications

Abstract

In the Early Villafranchian, the territory between Barga and Gallicano (Lucca, Tuscany), along the Serchio river, was a lacustrine basin, whose distinctive sediments are clays and clayey sands with layers of lignite. The Tùrrite di Gallicano, a torrent that has its source in the Apuan Alps, is an affluent of the Serchio river; along its lower course outcrop typical deposits of alluvial fan, that consist of calcareous gravels and conglomerates with rare clayey-sand interbeddings. These deposits, which show a heteropic passage to the lacustrine clays, have an Early Villafranchian age; consequently, the Tùrrite was a tributary of the ancient lake. Since that time, the torrent has not substantially changed its course, while some variations of the lithological composition of alluvial contribution took place. By reconstruction of the original surface of the ancient alluvial fan, it presently results that, at Barga, such deposits are more than 300 m higher than their primitive position. This difference in altitude documents an uplift of the Barga zone, that happened after the Middle-Late Pleistocene. Finally, the authors trace a synthetic picture of the evolutionary history of the region.