International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Fixing a J/K boundary: A comparative account of key Tithonian–Berriasian profiles in the departments of Drôme and Hautes-Alpes, France

Published: 01 Feb 2020

Pages: 24 - 46

DOI: https://doi.org/10.31577/GeolCarp.71.1.3

Authors: WILLIAM A.P. WIMBLEDON, DANIELA REHÁKOVÁ, ANDREA SVOBODOVÁ, PETR SCHNABL, PETR PRUNER, TIIU ELBRA, KRISTÝNA ŠIFNEROVÁ, ŠIMON KDÝR, CAMILLE FRAU, JOHANN SCHNYDER, BRUNO GALBRUN

Abstract: This work summarises the results of ten years of study of the palaeomagnetism and biostratigraphy of Tithonian–Berriasian profiles in the middle Vocontian Basin: at Le Chouet, Le Ravin de Font de Saint Bertrand, Charens, Belvedere (Haute Beaume) and Tré Maroua. This study has thus focussed on the “Calcaires Blancs vocontiens”, a predominantly micritic formation developed locally in microfacies categories SMF 2, SMF 3 and SMF 4. Facies zones FZ 3 and FZ 4 indicate deposition in upper to mid slope environments. We record key biotic markers across the J/K boundary, notably the primary marker Calpionella alpina, and supporting secondary datums founded on calpionellid, calcareous nannofossil, calcareous dinoflagellate and ammonite occurrences. All this is keyed to the Global Polarity Time Scale. Here we recognise the Tithonian/Berriasian boundary as coincident with the base of the Alpina Subzone (Calpionella Zone). Geographically, this is the most widespread correlatable datum in the traditional boundary interval, and it can be calibrated with other widespread fossil markers in magnetozone M19n.

Keywords: Jurassic/Cretaceous boundary, Berriasian, Tithonian, calpionellids, calcareous nannofossils, magnetostratigraphy, ammonites

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Volume 71 no. 1 / February 2020