In Quest of the Burdigalian GSSP: New Magnetostratigraphy of Odp Sites 1264/1265, 19-21.5 Ma

The detailed reconstruction of Earth’s history requires a robust and standard Geologic Time Scale (GTS). Over the last decades, a major effort has been made to establish an orbitally tuned stratigraphic framework for the Neogene to which nearly all GSSPs have been tied. The only remaining Neogene stage without a formally defined base is the Burdigalian. Different primary criteria have been proposed for the definition of this GSSP such as calcareous plankton bio-events and paleomagnetic reversals. Furthermore, various locations including (I)ODP cores and land-based sections have been suggested as potential candidates to define the GSSP. A strong candidate for the Burdigalian GSSP is ODP Site 1264 in the southeastern Atlantic, which is known for its robust astronomical tuning and excellent, high-resolution stable isotope and carbonate records. However, the magnetostratigraphy of this site is notoriously poor and unreliable because of potential coring-related deformations. Recently, the cores of Sites 1264 and 1265 have been sampled in high resolution to study the paleomagnetic signal in the critical boundary interval suggested in GTS2004-2020. In this talk, I will present a new magnetostratigraphy of both ODP Sites 1264 and 1265 for the interval spanning 19 to 21.5 Ma; it has been constructed by applying stepwise alternating field demagnetization on the samples at the Paleomagnetic Laboratory “Fort Hoofddijk”, Utrecht University, the Netherlands. The resultant, much improved magnetostratigraphy and linked astronomical ages for (sub)chron boundaries make these sites suitable for the placement of the Burdigalian GSSP at one of the recorded magnetic reversals. Nevertheless, alternative younger primary criteria have been suggested as well. This asks for an extension of the magnetostratigraphy of Sites 1264/1265, while also the shipboard calcareous plankton biostratigraphy has to be improved.