Sedimentology of the northwestern shores of the Ría de Arosa (NW Spain)

A study of the beaches on the NW shores of the Ría de Arosa was made with respect to shape and structure of the beaches, grain-size distributions, heavy mineral associations, and relations of the heavy minerals to the bedrock of the hinterland. Most of these numerous small beaches are situated in inlets determined by the occurrence of relatively weak bedrock (mostly schists). Grain-size generally fall in fractions > 50 µ, and some beaches even contain important amounts > 2000 µ. Many grain-size distributions are bimodal owing to the mixing of different beach layers by wave action or, in a few cases, to mixing with fluvial sands. The heavy mineral compositions of the fluvial and beach deposits approximately reflect the mineral compositions of the bedrock, especially in the deeper inlets of the Ría, whereas most of the beaches on the more exposed parts have a more varied heavy mineral composition. In some cases the minerals indicate a weak long-shore transport of the sands.