Characterization and astronomically calibrated age of the first occurrence ofTurborotalia frontosain the Gorrondatxe section, a prospective Lutetian GSSP: implications for the Eocene time scale

Abstract

The Gorrondatxe section, a prospective Lutetian Global Stratotype Section and Point (GSSP), has recently been used as the master reference section to reassess the correlation between Eocene magnetostratigraphic and calcareous planktonic biostratigraphic scales. However, the exact calibration of some events remained ill defined, as they were thought to be missing in Gorrondatxe due to a fault. The most important missing events were the first occurrence of the planktonic foraminifera Turborotalia frontosa and the C22n/C21r chron boundary. Either might be a reliable correlation criterion for the Ypresian/Lutetian boundary, as both approach the age of the original Lutetian Stratotype. New studies allowed the identification of the former event 9 m above the Gorrondatxe fault, within magnetic polarity Chron C21r and calcareous nannofossil Zone CP12a. Distinctive test features that characterize the most primitive morphotype of T. frontosa are described. Despite the high turbidite content, recurrent pelagic limestone–marl couplets and bundles occur, whose formation was driven by precession and eccentricity astronomical cycles. The first occurrence of T. frontosa was found 27 couplets and 5.5 bundles (60 m) below the first occurrence of the calcareous nannofossil Blackites inflatus, which is dated at 48 Ma. Hence, the age of the first occurrence of T. frontosa is estimated at 48.55 Ma, confirming that it is the most suitable planktonic foraminiferal correlation criterion for the Ypresian/Lutetian boundary. These results show that the stratigraphic interval missing due to the Gorrondatxe fault cannot be greater than a few metres and reinforce the value of this section as a prospective Lutetian GSSP.

Early Eocene climatic optimum: Environmental impact on the North Iberian continental margin

“…The age dating of the succession was based on previously published planktic foraminifera and calcareous nannofossil studies (Orue-Etxebarria et al, 1984;Bernaola et al, 2006aBernaola et al, , 2006bPayros et al, 2007Payros et al, , 2009aPayros et al, , 2009bPayros et al, , 2011.…”

Reassessment of the Early-Middle Eocene Planktic Foraminiferal Biomagnetochronology: New Evidence From the Tethyan Possagno Section (Ne Italy) and Western North Atlantic Ocean Odp Site 1051

“…This event occurs within C21r at ,47.76 Ma (Gradstein et al, 2004). The planktic foraminiferal event closest to the boundary is the B of T. frontosa (primitive forms), estimated to be ,550 kyr older than the B. inflatus datum (Payros et al, 2009). For now a detailed, integrated high-resolution record of the Ypresian/Lutetian transition is represented exclusively by the Spanish sections and further documentation/confirmation of biochronological data from other localities is essential to confirm the GSSP information.…”

“…The oldest specimens attributed to Turborotalia frontosa have been classified here following the broad taxonomical concept of Payros et al (2009) that primitive specimens show a slightly reduced size, a lower apertural arc, and a less inflated last chamber with respect to the typical morphotypes.…”

Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale

“…The enhancements in deep sea drilling recovery, multiple coring, high resolution sampling both offshore and onshore, has improved the calibrations with the magnetostratigraphy and/or modified the species ranges and allowed many of the planktonic foraminiferal bioevents to be revised. For example, detailed biostratigraphic investigations from Ceara Rise Pearson and Chaisson, 1997;Turco et al, 2002), equatorial Pacific Ocean (Wade et al, 2007), Indian Ocean (Hancock et al, 2002) and the Gorrondaxte and Agost sections in Spain (Payros et al, , 2009Larrasoaña et al, 2008;Ortiz et al, 2008) have resulted in revision of the calibrations of numerous bioevents. Most of these changes are small and incremental in nature, but some (e.g., the revision of the lower-middle Eocene by Payros et al, 2007) are major developments.…”