Palaeoclimate and diagenesis in the red limestones of Ereño (upper Aptian-lower Albian, Bizkaia)

Carbon and Oxygen isotopic values measured on rudist and Chondrodonta sp. shells from the red urgonian limestones of Ereño (Upper Aptian-Lower Albian, Bizkaia) have been demonstrated to be a very useful tool for reconstruction of both palaeoenvironmental features and diagenetic conditions that affected the famous ornamental stone. The δ18O‰ (PDB) values obtained from rudist recrystallized hipostraca suggest an influence of increasing diagenetic temperatures rather than the action of meteoric waters during early diagenetic stages. On the other hand, the δ18O‰ (PDB) values from diagenetically less-affected shells (Chondrodonta sp.) and parts of the shells (rudist miostraca) reveal palaeotemperatures of 19-27ºC very close to those of coetaneous marine waters and compatible with the seasonal variations described for a 30ºN palaeolatitude in the Tethys domain. Palaeoesalinities in the marine waters of the Ereño platform could oscillate between 32-36‰, slightly above the normal values recorded at presen