Geologic characterization of sedimentary rocks and sediments associated to shallows of El Confital Bay (NE of Gran Canaria island, Canary Islands)

Abstract

The shallows of Fernando, Roquerillos and Zabala are located in the NE of El Confital Bay, in depths comprised between -15 and -25m, they form submarine platforms with walls smaller than 7 m. Except the lower part of Roquerillos where we can find volcanic materials, the rest of rocks which compose the three shallows are sedimentary detritic rocks, in a lower proportion, some levels of conglomerate appear. In the shallows of Fernando and Roquerillos lithoclasts grains predominate (90-60%) over the bioclasts (38-5%). The lithoclasts are mainly fragments of felsic materials (43-4%), and in lower proportion fragments of mafic materials (33-7%). Referring to Zabala, the proportions of lithoclasts and bioclasts are similar, near the 50 % with abundance of felsic (30- 8%) over the mafic (16-5%). The porosity of these rocks is intragranular and intergranular, and the carbonated cement of calcite and aragonite is essentially LCM and poor in Sr. Moreover, the petrographies of sands are heterogeneity , in Fernando bioclasts sometimes predominate with values between 60% and 32%, in Roquerillos deposits of gravel-sized rhodolites are plentiful, and the sands which appear occasionally are felsic lithoclasts (about 77%) predominating over the mafic grains, in Zabala have similar percentages of lithoclasts and bioclasts, about 50% .