Fases diagenéticas en conchas de rudistas caprotínidos y monopléuridos del Complejo Urgoniano de la Punta del Castillo (Albiense inferior, Gorliz, Bizkaia)

Abstract

The Urgonian limestones of El Castillo Cape (lower Albian) were deposited in a shallow platform in which developed rudist and coral constructions. A further karstification created caves at metrical scale filled by sandy deposits. The rudist assemblages consist largely on bouquets and thickets of caprotinids in whose interspaces grew bouquets of monopleurids. A complex diagenetic history occurred upon both caprotinid and monopleurid shells, from early stages (vadose meteoric dissolution) to more advanced ones (neomorphism and selective dolomitization) to later ones (stylolitization and tectonic fracturing). The monopleurid hipostracum seems to be the more alterable part of the shell, because it appears frequently dissolved and filled by micrite. On the other hand, the hipostracum of caprotinids shows in some cases its original aragonitic prismatic polygonal microstructure partially preserved, in a major degree when close to micritic zones in which the water movement was restrained