Transferencias arenosas transversales y longitudinales entre playas apoyadas y dunas asociadas en la costa de Asturias (NO de la Península Ibérica)

Resumo

In the embayed sandy beaches of the cliff coast of NW Spain (Iberian Peninsula), the siliciclastic sands are mainly supplied by fluvial inputs, while carbonates sands (bioclasts) come from the organisms that colonize the peritidal rocky shore, some inherited. The sedimentological characteristics of these coastal deposits are studied over a wide segment of more than 387 km on the coast of Asturias. From the range (coarse centile) and the inclusive graphical granulometric parameters, as well as the composition of silica/ biogenic carbonate rate, can be deduced the transverse transfers between the beach and the associated aeolian dune field, and the longitudinal distribution in accordance with several coastal sections. Generally, from the beach to the aeolian dune field the average mean grain size decreases, the sorting improves, and percentage of biogenic carbonate falls; and, from an embayed beach to the adjacent one, a W-E downcurrent can be inferred due to the sand coastal drift. Large rivers have high siliciclastic discharges that are homogenized with the carbonate bioclasts from the estuarine mouths, whereas maximum carbonates are related with regional and local upwellings. This happens when the coastal current hits against some large promontory or due to the input of nutrient substances from estuaries containing wide, well-developed tidal flats and marshes which increase the proportion of peritidal organisms.