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The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 1

Wimbledon William A.P., Reháková Daniela, Svobodová Andrea, Elbra Tiiu, Schnabl Petr, Pruner Petr, Šifnerová Krýstina, Kdýr Šimon, Dzyuba Oksana, Schnyder Johann, Galbrun Bruno, Košťák Martin, Vaňková Lucie, Copestake Philip, Hunt Christopher O., Riccardi Alberto, Poulton Terry P., Bulot Luc G., Frau Camille, De Lena Luis

Volumina Jurassica

2020

Vol. 18, no. 1

53--106

Here in the first part of this publication we discuss the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on the established methods for correlation in the Tithonian/Berriasian interval. This will be followed, in the second part, by an account of the stratigraphic evidence that justifies the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. Here we discuss the possibilities for correlation in the historical J/K boundary interval, and the evolution of thinking on the positioning of the boundary over recent generations, and in relation to research in the last ten years. The Tithonian/Berriasian boundary level is accepted as occurring within magnetosubzone M19n.2n. The detailed distribution of calpionellids has been recorded at numerous sites, tied to magnetostratigraphy, and the base of the calpionellid Alpina Zone is taken to define the base of the Berriasian Stage. This is at a level just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We discuss a wide range of magnetostratigraphic and biostratigraphic data from key localities globally, in the type Berriasian areas of France and wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia etc.). The characteristic datums that typify the J/K boundary interval in Tethys and its extensions are detailed, and the correlative viability of various fossil groups is discussed. The boundary level is correlated to well-known J/K sections globally, and a series of secondary markers and proxies are indicated which assist wider correlation. Particularly significant are the primary basal Berriasian marker, the base of the Alpina Subzone (marked by dominance of small Calpionella alpina, Crassicollaria parvula and Tintinopsella carpathica) and secondary markers bracketing the base of the Calpionella Zone, notably the FOs of the calcareous nannofossil species Nannoconus wintereri (just below the boundary) and the FO of Nannoconus steinmannii minor (just above). Notable proxies for the boundary are: 1) the base of the A rctoteuthis tehamaensis Zone in boreal and subboreal regions, 2) the dated base of the Alpina Subzone at 140.22 ±0.14 Ma, which also gives a precise age estimate for the system boundary; and 3) the base of radiolarian “unitary zone” 14, which is situated just above the base of the Alpina Subzone.

New biostratigraphic evidence (calcareous nannofossils, ostracods, foraminifers, ammonites, inoceramids) on the Middle Coniacian in the eastern Bohemian Cretaceous Basin

Svobodova Andrea, Kočí Tomáš, Kočová-Veselská Martina, Ferré Bruno, Košťák Martin, Čech Stanislav, Chroustová Markéta

Geological Quarterly

2019

Vol. 63, No. 3

586--602

The classical locality of Svinary in the eastern Bohemian Cretaceous Basin is the site of new biostratigraphic investigations. Besides some scarce macrofossil evidence, bulk sediment samples were processed to retrieve micropalaeontological assemblages, and calcareous nannofossil smear slides were analysed. The studied material provided calcareous nannofossil assemblages including Micula staurophora, Lithastrinus septenarius and Broinsonia parca expansa, thus documenting the Middle Coniacian (upper part of UC10 Zone and lower part of UC11 Zone). The foraminifera assemblage is relatively rich, planktonic species show a wide stratigraphical range, while the benthic association represented by Neoflabellina suturalis suturalis and Gaudryina carinata is very similar to the Coniacian biozone of Stensioeina granulata-Eponides whitei, valid for the Bohemian Cretaceous Basin. Ostracods are represented by two common cytherellid species, and two rare ornamented species: Imhotepia marssoni? and Pterygocythereis spinosa. Inoceramid bivalves, namely Platyceramus mantelli, and a newly recorded ammonite, Tridenticeras tridens, support the late Middle Coniacian age of the Svinary outcrop. New biostratigraphic results are given along with palaeoecological interpretations of newly collected fossil material.