Annual Report 2011 of the Ypresian/Lutetian Boundary Stratotype Working Group

The Global Stratotype Section and Point (GSSP) for the base of the Lutetian Stage (early/middle Eocene boundary) was defined at 167.85 meters in the Gorrondatxe sea-cliff section (NW of Bilbao city, Basque Country, northern Spain; 43º 22’ 46.47’’N, 3º 00’ 51.61’’ W). This dark marly level coincides with the lowest occurrence of the calcareous nannofossil Blackites inflatus (CP12a/b boundary), is in the middle of polarity Chron C21r, and has been interpreted as the maximum-flooding surface of a depositional sequence that may be global in extent. The GSSP age is approximately 800 kyr (39 precession cycles) younger than the beginning of polarity Chron C21r, or ~47.8 Ma in the GTS04 time scale.
The GSSP was approved by the International Commission of Stratigraphy in January 2011, and ratified by the International Union of Geological Sciences in 2011. Finally, the GSSP was officially published in Episodes:

Molina E., Alegret L., Apellaniz E., Bernaola G., Caballero F., Dinarès-Turell J., Hardenbol J., Heilman-Clausen C., Larrasoaña J.C., Luterbacher H., Monechi S., Ortiz S. Orue-Etxebarria X., Payros A., Pujalte V. Rodríguez-Tovar F.J., Tori F., Tosquella J. & Uchman A. (2011). The Global Stratotype Section and Point (GSSP) for the base of the Lutetian Stage at the Gorrondatxe
section, Spain. Episodes. 34(2), 86-108.

Report by Eustoquio Molina, Chairman.

Annual Report 2010 of the Ypresian/Lutetian Boundary Stratotype Working Group

The Ypresian/Lutetian boundary Stratotype was defined at the Gorrondatxe section, which is an excellent very expanded and continuous section. The Ypresian/Lutetian Working Group decided, during the final Workshop in Getxo (near Bilbao, Spain) on September 26, 2009, to propose the Lutetian GSSP at meter 167.85 of the Gorrondatxe section in a dark marly level where the nannofossil Blackites inflatus lowest occurs, approximately 47.76 Ma ago. Two candidate sections, Agost and Gorrondatxe, were proposed and the Lutetian GSSP at Gorrondatxe was elected by consensus after fruitful discussions. The proposal was voted in 2010 by the ISPS vonting members and was approved. Recently the proposal was sent to ICS in order to be voted. The following papers co-authored by the members of the Y/L Working Group were published or are in press:

Rodríguez-Tovar F.J., Uchman A., Payros A., Orue-Etxebarria X., Apellaniz E. and Molina E., (2010). Sea-level dynamic and palaecological factors affecting trace fossil distribution in Eocene turbiditic deposits from the Gorrondatxe section, N Spain. Palaeogeography, Palaeoclimatology, Palaeoecology, 285, 50-65.

Ortiz, S., Alegret, L., Payros, A., Orue-Etxebarria, X., Apellaniz, E. and Molina, E., (in press). Distribution patterns of benthic foraminifera across the Ypresian-Lutetian Gorrondatxe section, Northern Spain: response to sedimentary disturbance. Marine Micropaleontology, doi:10.1016/j.marmicro.2010.09.004

Payros, A., Dinarès-Turell, J., Bernaola, G., Orue-Etxebarria, X., Apellaniz, E. and Tosquella, J., (in press). On the age of the Early/Middle Eocene boundary and other related events: cyclostratigraphic refinements from the Pyrenean Otsakar section and the Lutetian GSSP. Geological Magazine, doi:10.1017/S0016756810000890.

Report by Eustoquio Molina, Chairman.

Annual Report 2009 of the Ypresian/Lutetian Boundary Stratotype Working Group

After many years searching for a suitable section to define the Ypresian/Lutetian boundary Stratotype, the Gorrondatxe section was found and the Lutetian GSSP was defined in a very expanded and continuous section. The Ypresian/Lutetian Working Group decided, during the final Workshop in Getxo (near Bilbao, Spain) in September 26, 2009, to define the Lutetian GSSP at meter 167.85 of the Gorrondatxe section in a dark marly level where the nannofossil Blackites inflatus first appears, approximately 48 Ma ago. Two candidate sections Agost and Gorrondatxe where proposed and the Lutetian GSSP at Gorrondatxe was elected by consensus after long discussions. All the events near the base of the Lutetian Stage were discussed and it was considered that the absence of B. inflatus is not so certain and relevant like the presence of B. inflatus in the lower sample of the Lutetian Stage Stratotype found by Aubry (1986) in Palaeo.Palaeo.Palaeo. The FO of Discoaster sublodoensis was considered too old because it appears in Chron 22n, which is clearly Ypresian. Consequently, it was considered that the FO of B. inflatus is the best marker because it appears at or just below the base of the Lutetian Stage Stratotype of Paris. Furthermore, in the lower Lutetian of Paris there is Nummulites laevigatus and in Gorrondatxe the first sample above, with larger foraminifera, contains the first Nummulites laevigatus like in the Paris bassin. Planktic foraminifera were not used because of their absence in the Lutetian Stage Stratotype in Paris. Nevertheless, it is clear that the first appearance of Hantkenina in all the sections studied is about 4 Ma younger than the FO of B. inflatus. The report to be voted by ISPS, ICS and IUGS is being prepared. The following papers co-authored by the members of the Y/L Working Group were published:

Larrasoaña, J.C., Gonzalvo, C., Molina, E., Monechi, S., Ortiz, S., Tori, F. & Tosquella, J. (2008). Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): implications for defining the Ypresian/Lutetian boundary stratotype. Lethaia. 41, 395-415.

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. 69, 297-313.

Payros, A., Orue-Etxebarria, X., Bernaola, G., Apellaniz, E., Dinarès-Turell, J., Tosquella, J., & Caballero, F., (2008). Characterization and astronomically calibrated age of the first occurrence of Turborotalia frontosa in the Gorrondatxe section, a prospective Lutetian GSSP: implications for the Eocene time scale. Lethaia. 42, 255-264.

Payros, A., Tosquella, J., Bernaola, G., Dinarès-Turell, J., Orue-Etxebarria, X. & Pujalte, V. (2009). Filling the North European Early/Middle Eocene (Ypresian/Lutetian) boundary gap: Insights from the Pyrenean continental to deep-marine record. Palaeogeography, Palaeoclimatology, Palaeoecology. 280, 313-332.

Report by Eustoquio Molina, Chairman

Annual Report 2008 of the Ypresian/Lutetian Boundary Stratotype Working Group

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

Annual Report 2006 of the Ypresian/Lutetian Boundary Stratotype Working Group

The new section found last year in Agost, Betic Cordillera, Alicante province (Spain) 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. This section is a suitable candidate to define the Ypresian/Lutetian boundary.
Another suitable candidate found last year is the Gorrondatxe beach section, W Pyrenees, Basque country (Spain). A high-resolution multi-disciplinary study, including physical stratigraphy (lithostratigraphy, sequence stratigraphy and magnetostratigraphy) and biostratigraphy (calcareous nannofossils, planktic and larger foraminifera) has been carried out over the 700 m thick Gorrondatxe section by Orue-Etxebarria et al. (2006).
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 this boundary will be selected in 2007, before to choose one of these sections to place the Ypresian/Lutetian boundary, and the best section will be choose and the GSSP proposed before the Geological Congress in 2008.

Reference:
Orue-Etxebarria, X., Payros, A., Bernaola, G., Dinarès-Turell, J., Tosquella, J., Apellaniz, E. and Caballero F. (2006) The Ypresian/Lutetian boundary at the Gorrontatxe beach section (Basque country, W Pyrenees). Mid-Conference Field Excursion Guidebook, Climate & Biota of the Early Paleogene, Bilbao, 33 pp.

Report by Eustoquio Molina, Chairman

Annual Report 2005 of the Ypresian/Lutetian Boundary Stratotype Working Group

In Agost, Alicante province (Spain) was recently found a good section, which seems to be the most suitable candidate for the definition of the Ypresian/Lutetian Boundary Stratotype. It is a new section placed 1 km west of the section studied by Molina et al. (2000).

Planktic foraminiferal biostratigraphy indicated that the new section is more continuous, better exposed and more expanded. The Hantkenina first appearance, which is considered the best correlation criterion, is located in the middle part of the section in a good exposed interval.

As this new section is the most suitable candidate, an exhaustive stratigraphical study is being carried out. The magnetostratigraphical study reveals a series of reversed and normal chrons, which are now being interpreted and integrated with the biostratigraphical data (planktic foraminifera, small benthic foraminifera, larger foraminifera and calcareous nannofossils).

Formal contacts with the local authorities have been initiated in order to preserve the site. If everything goes well the GSSP could be completed and proposed to ISPS in the year 2007.

Report by Eustoquio Molina, Chairman

Annual Report 2004 of the Ypresian/Lutetian Boundary Stratotype Working Group


In 2003-2004 the Ypresian/Lutetian Boundary Stratotype Working Group continued the search of a suitable section in which eventually define the GSSP.
The Punta Torcida section in Argentina was visited and sampled, but unfortunately is not a good candidate, since in shallow marine environments, such as the Austral Basin in Tierra del Fuego, there is a widespread hiatus between the Early and Middle Eocene (Olivero and Malumian, 1999).
The Spanish subgroup was looking for a suitable section in the Betic cordillera (Southern Spain). Recently, a new section has been found in the Agost region about one kilometre far from the section studied by Molina et al. (2000). This new section is better exposed and could be a suitable candidate. Both sections seem to be continuous and show a good record of the Ypresian/Lutetian event caused by a major see level drop.
A detailed study of the Fortuna section, also located in the Betic cordillera, was finished, integrating the data of foraminifera by Gonzalvo, Molina, Ortiz and Thomas, calcareous nannofossils by von Salis, stable isotopes by Schmitz and mineralogy by Mancheño. Furthermore, two papers were published regarding the planktic and small bethic foraminifera, which allowed to recognize a hyperthermal event (Ortiz and Molina, 2003; Gonzalvo and Molina, 2003). The result shows that the Agost section is probably better than the Fortuna section, which was considered the leading candidate section previously.

In order to inform and generate a more active participation a web site was created, that can be visited at the following address:

http://wzar.unizar.es/perso/emolina/ypresian.html

This web site is up-dated frequently to explain the aims, how and where to define the boundary stratotype, which are the best potential sections, who are participating in the working group and what is the more recent bibliography on the Ypresian/Lutetian boundary.

References:

Molina E., Cosovic V., Gonzalvo C & von Salis K. (2000). Integrated biostratigraphy across the Ypresian/Lutetian boundary at Agost, Spain. Revue de Micropaléontologie. 43(3), 381-391.

Olivero E. B. & Malumian N. (1999). Eocene Stratigraphy of Southeastern Tierra del Fuego Island, Argentina. AAPG Bulletin. 83(2), 295-313.

Ortiz S. & Molina E. (2003). Foraminíferos bentónicos como indicadores de un evento hipertermal en el tránsito Ypresiense-Luteciense del corte de Fortuna (Murcia, Cordillera Bética). Geotemas. 5, 185-188.

Gonzalvo C. & Molina E. (2003). Bioestratigrafía con foraminíferos planctónicos del límite Ypresiense/Luteciense de Fortuna (Cordilleras Béticas, España). Geotemas. 5, 113-116.

Report by Eustoquio Molina, Chairman.