Provenance analysis of submerged and emerged sands of five beaches in Telde southern coast

Abstract

The nature of thesubtidal, intertidal and supratidal sands of five beaches on the southern coast of the municipality of Telde (E of Gran Canaria) has been studied. Thus, the origin analysis of 29 sand samples has been carried out through petrographic studies of grain identification and point counting (200identificationsper thin section). The results confirm that there are two types of beaches, one with blackish dark sands (Salinetas) that is rich in volcanic terrigenous (fragments of rock and mafic and felsic minerals) and intraclasts, with a mean percentage of abundance of lithoclast 87.4% and of bioclasts 12.6% (σ = 5,6), being the fragments ofmafic rock and ferromagnesian minerals the most frequent. The rest of the beaches (Aguadulce, Ojos de Garza, Ámbar and Gando) show lighter beige colors as they are richer in bioclasts (with average values of 37.9% σ = 10.5, 30.9 σ = 5.1; 47.6% σ = 13.4,32.2% σ = 8.1, respectively), being the flora grains (rhodoliths) more abundant than those of fauna (mollusks and, to a lesser extent, foraminifera, echinoderms and bryozoans). There is no homogeneity of data between the submerged and emerged sands in each beach, so the coastal dynamics and the wind are not able to balance the values of abundance. Likewise, the variations found in the nature of the sands in these 5 beaches are due to different natural coastal geomorphological factors (for example, orientation of the beach line, presence of sedimentary and volcanic rocky, substrates and cliffs, existence of ravinemouth, etc.)and/oranthropic conditions (urban and natural beaches, different coastal management, etc.).