A meeting of the French working groups on Jurassic and Cretaceous stratigraphy (Reunion Conjointe GFC/Groupe Jurassique de la section STRATI) was held on 2-3 December 2024 at the Sorbonne University (Paris).

The special guest of the meeting was Prof. Jacek Grabowski from the Polish Geological Institute – National Research Institute, who presented a lecture entitled The Jurassic/Cretaceous boundary: A short review of recent developments, outlining the current state of research on dating and global correlation of the boundary between the Jurassic and Cretaceous systems.

Prof. J. Grabowski is the chairman of the international Berriasian Working Group responsible for developing a global standard for the Jurassic-Cretaceous boundary. This is the only stratigraphic boundary of this stature that does not yet have a formal and universally accepted definition.

PhD Damian G. Lodowski (PGI-NRI) and PhD Justyna Kowal-Kasprzyk (AGH University of Science and Technology in Cracow) also participated in the meeting. They presented new data on biostratigraphy of Jurassic and Cretaceous boundary French profiles from the Vocontian Basin (south-eastern France), based on microfossils (calpionellids and calcareous dinocysts), and the first results of stratigraphic calibration of pelagic tytonian and berrasian formations on the basis of orbital cycles.

The conference was followed by a field trip to the Boulonnais profile on the North Sea coast. The profile, located in a picturesque coastal cliff, exposes Upper Jurassic formations (Upper Meridian and Tithonian), which are the more shallow-water equivalent of the succession found in the Polish Basin (Pałuki Formation) and in southern England and the North Sea Basin (Kimmeridge Clay Formation).

Integrated stratigraphic studies of this profile (including magnetostratigraphy and chemostratigraphy), dated on the basis of ammonites and with a well-developed climate change succession (clay minerals), will be the subject of research by Polish and French scientists in the coming years.

General view of the Boulonnais profile. Prof. Jean-Francois Deconinck (University of Dijon) and Jacek Grabowski (PGI-NRI). Lower and middle tithonian boundary: Crèche sandstones (at the base of the cliff), and Crèche and Wimereux claystones (dark shales and marls in the lower part of the cliff). Upper part of the cliff – Oies sandstones and Purbeck carbonates (Jurassic/Cretaceous boundary)

Prof. Jacek Grabowski in front of the Croi shale and limestone cell (Argiles et calcaires de Croi, Middle Tithonian)

Prof. Jean-Francois Deconinck with Polish participants of the conference: PhD Justyna Kowal-Kasprzyk (GH University of Science and Technology in Cracow) and PhD Damian G. Lodowski (PGI-NRI)

Text: Jacek Grabowski