Geoarchaeological evidences of changes in the coastline progradation rate of the Versilia coastal plain between Camaiore and Viareggio (Tuscany, Italy): possible relationships with Late Holocene high-frequency transgressive-regressive cycles

Abstract

Bini M. et al., Geoarchaeological evidences of changes in the coastline progradation rate of the Versilia coastal plain
between Camaiore and Viareggio (Tuscany, Italy): possible relationships with Late Holocene high-frequency transgressive-regressive
cycles. (IT ISSN 0394-3356, 2009)
The Late Holocene progradation of the Versilia coastal-plain, between Camaiore and Viareggio (Tuscany, Italy), was investigated on
the basis of geomorphological, stratigraphical, and archaeological data. Five geomorphological units, corresponding to the Camaiore
alluvial fan, beach-dune ridges, interdune marshes, a back dune marsh (Giardo and related Massaciuccoli lake area), and the presentday beach, were identified.
Archaeological data provide some chronological constraints on the timing of Late Holocene coastal progradation. About 3000 yrs ago,
the coastline was located about 2,5 km landward in respect to its present-day position, in the proximity of the Migliarina beach dune,
behind which a marsh area developed. This marsh extended from the Giardo to the present-day Massaciuccoli Lake. The connection
between Giardo and Massaciuccoli area allows us to reconsider the role of Acquarella site in becoming an important centre in commercial communication among sea, coast, and inland areas. Around the 12th century the coastline was located in proximity of the dune alignments where Motrone Fort and the Castello Vecchio di Viareggio were built testifying a progradation of about 1,3 km. During the next four centuries the coastline continued its seaward shifting for 500 m more and was located in proximity of the Matilde Tower.
From the 16th to the present time the progradation of the coastline has been proceeded by of about 0,7 km. These data indicate changes in the progradation rate during that the time and in particular an increase since the 16th century. An irregular progradation rate agrees with stratigraphic and facies analysis based on surface and subsurface data (wells and excavations) that allowed us to define a preliminary framework of the last phases of coastline progradation. The identification of four high-frequency small-scale transgressiveregressive cycles (parasequences) within the succession recording the Late Holocene phase of progradation points to evidence that the progradation rate of the coastline was subject to cyclic fluctuations.