Date: December 17th 2018


Dear Colleagues,
here is a short report on the recent "International Symposium AROUND the Jurassic-Cretaceous Boundary" - JK2018.

A detailed report will be published later in an International Scientific Journal, 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).

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),

with a scientific partnership from 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 Commission"), Stratigraphy, Sedimentology and Palaeontology (SSP) - European Geosciences Union (EGU), International Association of Sedimentologists (IAS), Society for Sedimen
tary Geology (SEPM), The Paleontological Society),

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 http://cretaceous.stratigraphy.org/working-groups/berriasian-gssp-wg/, 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), 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, it is the base Berriasian (the primary marker is the base of the acme of Calpionella alpina, as designed by the Berriasian WG),
• 2nd option, it is the base Valanginian (the primary marker is the FAD of Calpionellites darderi, as designed by the Valanginian WG),
• 3rd and • 4th options, neither base Berriasian, nor base Valanginian.

The vote gave an absolute majority (52%) to the 2nd option, i.e., the base Valanginian as the base Cretaceous!

7% of the votes went to the 3rd option.
The Radiolarian people voted as a "single entity" (21%) for the base of the Berriasian, BUT with another marker (Radiolarian) than the primary marker selected by the Berriasian Working Group, although I mentioned several times that we should not question the decision of a working group!
The remaining 21% went to the 1st option, i.e., the base of the Berriasian, BUT again if some people agreed with the base of the acme of Calpionella alpina ... some other people disagreed with this marker selected by the Berriasian Working Group.

During the discussion, the chairperson -I- offered a voice mostly to those people who did not vote for the Valanginian (and even to people who did not vote at all).
Some people --very few-- 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!
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.

The Radiolarians' 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).

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, Enay, ...)!
We hope we shall be listened to ...

Bruno Granier

<< Previous: An international meeting in Geneva (CH) next December

| Archive Index |

 

(archive rss , atom )

this list's archives:


temporary list

Subscribe to Report:

|

Powered by Dada Mail 2.10.12
Copyright © 1999-2006, Simoni Creative.