Date: January 4th 2019

Dear Colleagues,
first please accept my apologies if this message is a duplicate (for instance, it was sent to all Carnets' subscribers!). You did/could not attend the JK2018 meeting but, for instance, you could be interested to know the result of a survey we made. I should mention that further to the announcement of the results of this survey (and the following discussion) we have received more supporting comments regarding the relocation of the JK boundary at the Valanginian boundary rather than at any of the Berriasian boundaries.

Hereafter there is a short report on the recent "International Symposium AROUND the Jurassic-Cretaceous Boundary" - JK2018. The "Carnets de Géologie" was a scientific partner of this meeting together with 15 national or international societies (Asociación Paleontológica Argentina (APA), Association Paléontologique et Évolutive Libanaise (APEL), Association Paléontologique Française (APF), Sociedad Española de Paleontología (SEP), Società Paleontologica Italiana (SPI), Societatea Paleontologilor din România (SPR), Comité Suisse de Stratigraphie (strati.CH), International Subcommission on Stratigraphic Classification (ISSC), International Research Group on Ostracoda (IRGO), Юрская комиссия МСК (Russian "Jurassic Commission"), Меловая комиссия МСК (Russian "Cretaceous Comm
ission"), Stratigraphy, Sedimentology and Palaeontology (SSP) - European Geosciences Union (EGU), International Association of Sedimentologists (IAS), Society for Sedimentary Geology (SEPM), The Paleontological Society).

The abstract volume should be available soon at Carnets Geol. (in full open access), and a number of papers associated to the meeting will be published a dedicated Virtual Special Issue at Cretaceous Research, entitled "Jurassic-Cretaceous Transition" (2 papers are already published, another manuscript is accepted pending minor modifications).

There were 74 registrations from 25 countries (Africa: Algeria, Morocco; Americas: Argentina, Chile, USA; Asia: China, Iraq, Japan, Jordan, Lebanon, Qatar, Thailand, Turkey; Europe: Denmark, France, Germany, Italy, Netherlands (the), Poland, Romania, Russian Federation, Slovenia, Spain, Switzerland, United Kingdom), 59 contributions (6 keynotes, 33 presentations, 25 posters including 5 to supplement regular oral presentations or keynotes) from 162 authors and coauthors (including 11 from the Berriasian WG, out of the 60 listed at, plus 3 former members of this WG, VERSUS 4 from the Valanginian WG).

The last day of the meeting, in order to have a FAIR and OPEN discussion on the system boundary (we did not discuss any stage boundaries or GSSP), there was a survey to tentatively measure attendees' opinions, perceptions and orientations. There were several options (with space for comments) for the Jurassic-Cretaceous system boundary:

• 1st option, the base Berriasian (the primary marker is the base of the acme of Calpionella alpina inside the M19n, as designed by the Berriasian WG) got 17% of the votes,
• 2nd option, the base Valanginian (the primary marker is the FAD of Calpionellites darderi, as designed by the Valanginian WG) got an ABSOLUTE MAJORITY (52%),
• 3rd option, the base Ryazanian got 7% of the votes,
• 4th option, a Radiolarian marker inside the M20n got 21 % of the votes (this option should be ruled out because, at this stage, it is in disagreement with the ICS's, ISCS's and Berriasian WG's decision).

During the discussion that followed, the chairperson -Bruno Granier- offered a voice mostly to those people who did not vote for the Valanginian (and even to people who did not vote at all). One person stated that "it is too late to change!"... which is ALL but a scientific justification (!):
1) The Gelasian was recently shifted into the Pleistocene (hence into the Quaternary);
2) The Tithonian-Berriasian boundary changed 3 times in the recent years!

The Radiolarian turnover take place in the late Tithonian (not at the stage boundary ... it is not even in the same magnetozone!). Several other fossil groups show a turnover at the Berriasian-Valanginian boundary (ammonites, foraminifers, calpionellids, ...) whereas there is no such event at the Tithonian-Berriasian boundary (except for the Calpionellids). Radiolarian people said they agreed to investigate the Berriasian-Valanginian boundary too (so far they were given priority to the sole Tithonian - Berriasian boundary).

Geochemistry demonstrates that the Jurassic does not end with the Tithonian but with the Berriasian. The Weissert event marks the dawn of the Cretaceous and its OAEs. Helmut Weissert himself stated that "Oppel was right!" (with the Titonische = Tithonian + Berriasian) because there is NO geochemical break near the Tithonian - Berriasian boundary. The system boundary has to be located at a stage boundary ... between the end of Oppel's Tithonische and the Weissert event (there is only one stage boundary that meets this requirement: the base Valanginian).

At the end of the day further to this open discussion, which was not "sterile" (!), it looks like a vast majority of people would like the option of the base Valanginian as the JK boundary to be fully reconsidered (particularly because it looks more stable and more easy to correlate). This large majority includes people who initially voted for the Valanginian (the absolute majority), people who changed their mind, and people who are not completely against considering it as a potential candidate for the system boundary.

In conclusion, today, it looks like the door is wide open for a real reconsideration of the Berriasian-Valanginian boundary as the base of the Cretaceous (sensu Orbigny, Oppel, Coquand, Énay, ...)!

Best wishes,
Bruno Granier

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