Alteración diagenética en conchas de rudistas caprotínidos del Complejo Urgoniano de la Punta del Castillo (Albiense inferior, Gorliz, Bizkaia)

The shallow marine carbonate platform sediments of El Castillo Cape (lower Albian, Gorliz, Bizkaia) bear rudists from the families Monopleuridae and Caprotinidae. The geochemical, isotopic and luminescent behavior of caprotinid shells allows to us to assure a different response to diagenetic processes in comparison with the monopleurid ones. A medium diagenetic degree for caprotinid shells is deduced from the constant cationic profiles, low Na+ and Sr2+ contents, high Mn2+ and Fe2+ values, together with the homogenized distribution of cathodoluminescence in the shells. The degradation of the interprismatic organic matter opened ways for circulation of diagenetic fluids that precipitated early cements of sintaxial High Magnesian Calcite upon prismatic crystals. The isotopic results of C and O confirm that the shells of monopleurids have a greater resistance to the alteration than those of caprotinids