Contenidos de CaCO3 en facies turbidíticas y presencia de celestita diagenética en el Maastrichtiense inferior (Sopelana, Arco Vasco)

Abstract

The westernmost Sopelana and «Punta de Solondotas» sea-cliff sections exposes a marl-limestone alternation distorted by thin turbidite layers, from the Lower Maastrichtian of the deep Basque Arc domain. High-resolution analysis (% CaCO3) of the Lower Maastrichtian turbidites and marls point out: a) a major content in turbidites than marls; b) a decrease tendency in carbonate content from the bottom towards the top of the bed. To explain the presence of unusual celestite (SrSO4) multilayers founded in deep marine sediments, a hypothetical biogenic source (acantharians) and complex diagenetic processes are invoked in order to develop «cone in cone» structure and a small silicification replacement. In the top of the «Punta de Solondotas» outcrop, we confirm that the early entry of deep, cold, oxygenated water produced a gradual (grey/red) change of coloration in the Lower Maastrichtian marls. It is the beginning of the Cretaceous oceanic red beds (CORB´s) in the Basque Cantabrian Basin