Biomagnetostratigraphic analysis of the Gorrondatxe section (Basque Country, Western Pyrenees): Its significance for the definition of the Ypresian/Lutetian boundary stratotype

Abstract

The Gorrondatxe beach section is part of a 2300 m thick lower Ypresian-upper Lutetian deep-water marine succession and contains the most extensive Ypresian/Lutetian boundary interval so far reported. The entire 700 m thick uppermost Ypresian, lower Lutetian succession shows a good magnetic signal and is rich in well-preserved calcareous planktonic fossils. Moreover, some of the interbedded turbidites supplied abundant nummulitids, allowing the correlation and calibration of the zonal schemes of larger foraminifers and calcareous plankton. At the Gorrondatxe section, all the events traditionally used to identify the Ypresian/Lutetian boundary occur at different levels, demonstrating that before selecting a section to place the Ypresian/Lutetian boundary stratotype the specific criterion to identify this boundary should be defined. The high-resolution calcareous plankton and larger foraminifer biostratigraphic studies, coupled with the magnetostratigraphic analysis performed in the Gorrondatxe section, show the complete record of events that characterizes the Ypresian/Lutetian boundary interval, highlighting the position of several marker events that are suitable to be selected as the criterion to define the Ypresian/Lutetian boundary. The Gorrondatxe section fulfils most of the requirements demanded of a Global Stratotype Section and Point (GSSP) by the International Commission on Stratigraphy, and consequently it is proposed here as a candidate for the GSSP of the base of the Lutetian.