Resumen de Contenidos de CaCO3 en los pares marga-caliza del Maastrichtiense y Daniense en Sopelana, Arco Vasco: facies grises frente a facies rojas
The Sopelana sea-cliff section exposes a continuous marl-limestone alternation from the Lower Maastrichtian to the Danian, in the deep Basque Arc domain. The high-resolution analysis (% CaCO3) of the Lower- Upper Maastrichtian couplets confirms a simple and regular layout versus a more complex behaviour of the Danian couplets. The marl and limestone mean values of the Upper Maastrichtian point out a continental debris enrichment. The early entry of deep, cold, oxygenated water produces a gradual (grey/ yellowgreenish/ red) change of coloration in the Lower Maastrichtian couplets. It is the beginning of the Cretaceous oceanic red beds (CORB´s). The �bleaching� around macrofossil nucleus and small fractures in the red facies shows a small diagenetic stage due to the influx of reducing fluids.
