Reassessment of the Early–Middle Eocene biomagnetochronology based on evidence from the Gorrondatxe section (Basque Country, western Pyrenees)

Authors

  • AITOR PAYROS,

  • GILEN BERNAOLA,

  • XABIER ORUE-ETXEBARRIA,

  • JAUME DINARÈS-TURELL,

  • JOSEP TOSQUELLA,

  • ESTIBALIZ APELLANIZ


Aitor Payros [a.payros@ehu.es], Gilen Bernaola [gilen.bernaola@ehu.es], Xabier Orue-etxebarria [xabi.orueetxebarria@ehu.es] and Estibaliz Apellaniz [estibaliz.apellaniz@ehu.es], Department of Stratigraphy and Palaeontology, Faculty of Science and Technology, University of the Basque Country, PO Box 644, E-48080 Bilbao, Spain; Jaume Dinarès-Turell [dinares@ingv.it], Istituto Nazionale di Geofisica e Vulcanologia, Laboratorio Di Paleomagnetismo, Via di Vigna Murata, 605, I-00143 Rome, Italy; Josep Tosquella [josep@uhu.es], Department of Geodynamics and Palaeontology, Faculty of Experimental Sciences, University of Huelva, Campus del Carmen, Avenida de las Fuerzas Armadas s/n, E-21071 Huelva, Spain.

Abstract

Thirteen Lower–Middle Eocene (Ypresian–Lutetian) successions, including the Gorrondatxe section in the western Pyrenees, show biomagnetostratigraphic correlation schemes that do not agree with the current standard framework. The main discrepancy concerns the position of the boundary between planktonic foraminiferal Zones P9 (=E7, approximately) and P10 (=E8, approximately), which was thought to occur within calcareous nannofossil Subzone CP12a and at the boundary between magnetic polarity Chrons C22n and C21r. However, in the differing correlation scheme the boundary between Zones P9 (=E7) and P10 (=E8) occurs close to the base of Subzone CP13a and to the boundary between Chrons C21n and C20r. An attempt at a new Ypresian–Lutetian boundary biomagnetochronology is made based on data from the Gorrondatxe section, which shows that the boundary between Zones P9 (=E7) and P10 (=E8) is 3.1 Myr younger than hitherto considered. Therefore, the duration of the Early Eocene, most commonly defined according to this planktonic foraminiferal zonal boundary, has generally been underestimated over the last four decades.

Ancillary