Biostratigraphic and magnetostratigraphic intercalibration of latest Cretaceous and Paleocene depositional sequences from the deep-water Basque basin, western Pyrenees, Spain

Latest Cretaceous (Late Maastrichtian) and Paleocene depositional sequences from the deep-water Basque basin have been calibrated with published [1,2] and newly acquired magnetostratigraphic data. Sequences mostly consist of hemipelagic marls and limestones, and their relative ages are well constrained with planktic foraminifera. They accumulated during a phase of tectonic tranquillity and reduced clastic input into the basin, and therefore they can be attributed to eustatic sea-level changes with reasonable confidence. On the basis of the planktic foraminifera zonation, a good match has been observed previously between the depositional sequences of the Basque basin and specific sea-level cycles of the 1988 version of the Exxon Global Cycle Chart (GCC) [3]. Here, a new attempt at correlation using their respective magnetostratigraphic data has failed to confirm such a match. The disagreements observed may indicate that, for the studied interval, (1) the current planktic foraminifera biostratigraphy lacks the necessary level of resolution to ensure synchrony between sequences of different basins, and/or (2) the magnetostratigraphy of the GCC needs to be revised. Whatever the case, the new findings lend support for some criticism on the use of the GCC for interregional correlations.