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Resumen:
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Based on a continuous succession of ammonite and calcareous nannofossil assemblages, the main purpose of this paper is the correlation between ammonite and calcareous nannofossil zone boundaries in two expanded sections from the Basque-Cantabrian area. The ammonite assemblages show clear euroboreal features and allow the identification of Pliensbachian-Toarcian zones and subzones established for NW Europe. Due to the presence of Mediterranean raxa documented at different levels, they are also helpful to improve the biocorrelations betv'een Boreal and Tethyan successions. The calcareous nannofossil assemblage changes provide a useful set of easily recognizable evenrs that facilitate the recognition of all the Pliensbachian-Toarcian zones described for NW Europe and Mediterranean Province. Based on the FO Similiscutum cruciulus (Jamesoni Zone), FO of Lotharingius hauffii (Stokesi/Margaritatus Zone boundary), FO of Carinolithus superbus (Serpentinus Zone), FO of Discorhabdus striatus (Serpentinus/Bifrons Zone boundary) and FO of Retecapsa incompta (lnsigneZone), the NJ3/NJ4, NJ4/NJ5, NJ5/NJ6, NJ6/NJ7 and NJ7/NJ8 Zone boundaries have been recognized. Besides, NJ4, NJ5 and NJ6 span almost the same ammonite-defined time internal in both NW Europe and Basque-Cantabrian area. With respect to the ammonite zone, the zone boundaries NJ3/NJa and NJ6/NJZ coincides with NJT3/NJT4 and NJT6/NJT7 proposed for Mediterranean Province. Instead, the zone boundaries NJ4/NJ5 and NJ5/NJ6 not coincides with NJT4/NJT5 and NJT5/NJT6 proposed for Mediterranean Province. Furthermore, in NW Europe and Mediterranean Province the FO of Retecapsa incompta is placed in the Levesquei Zone or Meneghinii Zone respectively, whilst in the Basque Cantabrian area it lies in the Insigne Zone.
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