Les Associacions de coralls plans (Scleractinia) de la plataforma carbonatada de Sant Corneli, unitat sud-pirinenca central (Cretaci superior, Santonià)

Abstract

The Santonian platy coral associations of the Catalan Pyrenees are studied. The associations form lenticular lithosomes over one metre thick with a high packing density of autochthonous platy coral colonies (lamellar and tabulo-lenticular). The specific richness is high (27 species), but the diversity is relatively low, with a clear dominance (73 %) of the coral Elasmofungia comoserioides Alloiteau. The corals must have been growing in calm water and low light intensity, protected from muddy sedimentation, on soft substrates on horizontal and relatively deep bottons. The episodic increase of the sedimentation rate would have caused a more or less progressive substitution of platy corals by rudists (bivalves) and domal corals, better adapted to the new conditions. This type of facies can be considerated a good palaeoenvironmental indicator of biotopes characterised by: (1) low light intensity, (2) low background sedimentation rates, (3) low hydrodynamic energy levels and (4) relatively deep water.