Lichenometric application to historical and subrecent dynamics and sediment transport of a Corsican stream (Figarella River—France)

Abstract

Lichenometry has been applied to blocks, canyon walls and terrace deposits. A growth curve, specific to Corsica, was made based on information obtained from tombstones, old monuments from the Genoese occupation of Corsica and Roman megaliths. This allowed us to create a curve going as far back as 2000 years. The curve is similar to those developed in Mediterranean environments (Cévennes and Eastern Pyrenees), but is very different from those developed in Alpine and Arctic regions. Lichens present on boulders of the bedload allow the time at which the boulders were laid down to be determined. The lichenometric study of the Figarella shows firstly that there is high stream competence. Blocks approximately 100 cm wide are moved during the 5-year flood. Recent important flood events were identified in 1973 and 1869. These correspond well with historical sources. Other older and much more important floods were also identified. This analysis has allowed us to extend the specific streampower curves proposed by Costa (Geol. Soc. Am. Bull. 94 (1983) 986) and Williams (Geogr. Ann. 65A (1983) 227) to blocks of more than 2 m wide. Lichens present on the canyon walls and on terrace sides in the plain allowed the last main incision phase to be dated to the Little Ice Age. Aerial photograph analysis has shown that the present braided system in the lower course of the river is no longer active.