Trasporto longshore e dispersione in profondità delle sabbie della costa di Bianco, Calabria ionica

The petrographic and textural analysis of river and beach sand of the 18,5 km long coastal tract spanning from Capo Bruzzano to Condoianni river mouth allowed to quantify the transversal sediment transport in the head of the Buonamico-Careri canyon and to define the Littoral Cells locally. The river sands feeding the Bianco coast (south) and Bovalino coast (north) are different both in terms of Q-F-L+C and Lm-Lv-C petrographic mode. Two basic sources are recognized: the Aspromonte provenance, characterizing the Laverde, Buonamico and Careri rivers and the Zomaro provenance, characterizing the Condoianni river. The beach samples of the Bianco coast petrographically coincide with the Laverde river while the beach sample of the Bovalino coast is petrographically similar to the Condoianni river. In a six km long segment of the Bianco coast the north-directed longshore transport affects significantly the mineralogic and textural maturity of sands; the amount of quartzose grains passes from 45 to 55% (Q-F-L+C mode) and the average roundness of quartz grains passes from 0,21 to 0,26 (Powers scale). The petrographic composition of beach sands of the Bovalino coast is poor of Lithic grains (L+C) and, among them, of Siliciclastic grains (Ls); this is not compatible with the north-directed longshore transport expected for the sediments delivered by the Buonamico and Careri rivers. On the contrary, the sands of the Bovalino coast are petrographically similar to the sands of the Zomaro province transported by the Condoianni river. Consequently, all of the flood sediments fed by the Buonarnico and Careri rivers must be incorporated by coastal rip currents that drive them at depth in the morphologic depression of the canyon. In the study area only one Littoral Cell can be formally defined; its limits are represented by the Capo Bruzzano headland to the south and the mouth of the Careri river to the north. The sediment input in the 10,9 km long coastal segment of the Cell is from the Laverde, Buonamico and Careri rivers. The sedimentary balance is highly negative because of the transversal transport in the canyon head facing the Buonarnico and Careri rivers. Further north, the Bovalino coast belongs to a distinct Littoral Cell which southern limit is still represented by the Careri river mouth.