The research has been focused on the study of the two more suitable sections to define the Lutetian GSSP: Agost and Gorrondatxe sections. The results of both sections show that the different events traditionally used to place the Ypresian/Lutetian boundary, previously thought to be almost simultaneous, actually occur at very different levels. The more close events to the base of the original Lutetian stage seem to be the first occurrence of the calcareous nannofossil Blackites inflatus at the base of Subzone CP12b and the first occurrence of the planktic foraminifera Turborotalia frontosa. The integrated magnetobiostratigraphic studies carried out at the Agost and Gorrondatxe sections provides conclusive evidence that both sections are almost continuous and contain diverse and well-preserved fossil groups. However, the Gorrondatxe section seems to be more suitable than the Agost section and it is now the leading candidate. The criterion and the section to precisely define the Ypresian/Lutetian boundary will be decided in September 2009 in a workshop of the Ypresian/Lutetian working group that will be organized near the Gorrondatxe section in Bilbao.
The following papers are in press:
Ortiz S., Gonzalvo C., Molina E., Rodríguez-Tovar F.J., Uchman A.,Vandemberghe N., Zeelmaekers E. (2008). Palaeoenvironmental turnover across the Ypresian-Lutetian transition at the Agost section, southeastern Spain: in search of a marker event to define the Stratotype for the base of the Lutetian Stage. Marine Micropaleontology. In press.
Larrasoaña J.C., Gonzalvo C., Molina E., Monechi S., Ortiz S., Tori F. y Tosquella J. (2008). Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): implications for defining the Ypresian/Lutetian boundary stratotype. Lethaia. In press.
Payros, A., Orue-Etxebarria, X., Bernaola, G., Apellaniz, E., Dinarès-Turell, J., Tosquella, J., Caballero, F., In press. Characterization and astronomically tuned age of the first occurrence of Turborotalia frontosa at Gorrondatxe, a prospective Lutetian GSSP: implications for the Eocene time scale. Lethaia.
Report by Eustoquio Molina, Chairman
Annual Report 2007 of the Ypresian/Lutetian Boundary Stratotype Working Group
A suitable GSSP candidate for the Lutetian Stage is the Gorrondatxe beach section, W Pyrenees, Basque country (Spain). A multi-disciplinary study, including physical stratigraphy (lithostratigraphy, sequence stratigraphy and magnetostratigraphy) and biostratigraphy (calcareous nannofossils, planktic and larger foraminifera) carried out over the 700 m thick Gorrondatxe section has been published by Payros et al. (2007).
Another suitable candidate is the Agost section, Betic Cordillera, Alicante province (Spain), which has been intensively studied. Biostratigraphy by means of planktic foraminifera, calcareous nannofossils, small benthic foraminifera and larger foraminifera indicated that the section is continuous and quite expanded. The magnetostratigraphical study reveals a series of reversed and normal chrons, which are now being interpreted and integrated with the biostratigraphical data. A paper by Larrasoaña et al. was recently submitted to Lethaia and another paper is in progress, including trace fossil and mineralogical data, to be submitted to Marine Micropaleontology. The results of both sections show that the different events traditionally used to place the Ypresian/Lutetian boundary, hitherto thought to be almost simultaneous actually occur at very different levels. The criterion to precisely define the Ypresian/Lutetian boundary will be selected in 2008 after the publication of the Agost results. Finally the best section will be chosen and the GSSP defined and proposed as soon as possible.
Reference:
Payros, A. Bernaola, G., Orue-Etxebarria, X., Dinares-Turel, J., Tosquella, J. and Apellaniz, E. (2007) Reasssesment of the Early-Middle Eocene biomagnetochronology based on evidence from the Gorrondatxe section (Basque Country, western Pyrenees). Lethaia, Vol. 40, pp. 183-195.
Report by Eustoquio Molina, Chairman