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Episodes 2016; 39(3): 460-481

Published online September 1, 2016

https://doi.org/10.18814/epiiugs/2016/v39i3/99741

Copyright © International Union of Geological Sciences.

Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)

Rogério Bordalo da Rocha1, Emanuela Mattioli2, Luís Vítor Duarte3, Bernard Pittet2, Serge Elmi2†, René Mouterde4†, Maria Cristina Cabral5, Maria José Comas-Rengifo6, Juan José Gómez7, António Goy6, Stephen P. Hesselbo8, Hugh C. Jenkyns9, Kate Littler8, Samuel Mailliot2a, Luiz Carlos Veiga de Oliveira10, Maria Luisa Osete11, Nicola Perilli12, Susana Pinto13, Christiane Ruget14 and Guillaume Suan2

1GeoBioTec and Earth Sciences Department, Faculty of Sciences and Technology, Universidade NOVA de Lisboa, 2829-516 Caparica (Portugal); Toarcian Task Group Convenor. E-mail: rbr@fct.unl.pt
2Univ Lyon, Université Claude Bernard Lyon 1, Ens de Lyon, CNRS, UMR 5276 LGL-TPE, F-69622, Villeurbanne, France. E-mail: emanuela.mattioli@univ-lyon1.fr, Toarcian Task Group Secretary; bernard.pittet@univ-lyon1.fr; guillaume.suan@univ-lyon1.fr
2aPresent address: Observatoire de Lyon, Université Lyon 1, Campus de la Doua, Bâtiment Geode, 69622 Villeurbanne Cedex (France). E-mail: samuel.mailliot@univ-lyon1.fr
2†Former Toarcian Working Group Convenor.
3MARE - University of Coimbra, Earth Sciences Department, Rua Silvio Lima, Polo II, Coimbra (Portugal). l E-mail: duarte@dct.uc.pt
4†Université Catholique de Lyon, France.
5Universidade de Lisboa, Faculdade de Ciências, Departamento de Geologia e Instituto Dom Luiz (IDL), Campo Grande, C6-40, 1749-016 Lisboa (Portugal). E-mail: mccabral@fc.ul.pt
6Departamento de Paleontologia, Facultad de Ciencias Geológicas, Univ. Complutense de Madrid. José António Novais, 2, 28040 Madrid (Spain). E-mail: mjcomas@ucm.es; angoy@geo.ucm.es
7Departamento de Estratigrafía, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid e IGEO (CSIC-UCM), José Antonio Novais 2, 28040 Madrid, España. E-mail: jgomez@ucm.es
8Camborne School of Mines, University of Exeter (United Kingdom). E-mail: S.P.Hesselbo@exeter.ac.uk; K.Littler@exeter.ac.uk
9Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN (United Kingdom). E-mail: hughj@earth.ox.ac.uk
10Petrobras University, Rua Ulisses Guimarães 565, 80 andar, 20211-225, Rio de Janeiro (Brazil). E-mail: lcveiga@petrobras.com.brlcveiga@petrobras.com.br
11Departamento de Física de la Tierra, Facultad de Ciencias Físicas, Avenida Complutense s/n, Universidad Complutense de Madrid and Instituto de Geociencias, IGEO, CSIC, 28040 Madrid (Spain). E-mail: mlosete@fis.ucm.es
12Dipartimento Scienze della Terra, Università degli Studi di Pisa, Via S. Maria 53, 56100 Pisa (Italy). E-mail: nicola.perilli@unipi.it
13Universidade de Lisboa, Faculdade de Ciências, Departamento de Geologia, Campo Grande, C6-40, 1749-016 Lisboa (Portugal). E-mail: susanapvpinto@gmail.com
14Chipier, Route de Pimotin, 69420 Tupin et Semons (France). E-mail: andrechris.ruget@gmail.com

Received: July 10, 2015; Accepted: February 18, 2016

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Global Stratotype Section and Point (GSSP) for the base of Toarcian Stage, Lower Jurassic, is placed at the base of micritic limestone bed 15e at Ponta do Trovão (Peniche, Lusitanian Basin, Portugal; coordinates: 39°22’15’’N, 9°23’07’’W), 80km north of Lisbon, and coincides with the mass occurrence of the ammonite Dactylioceras (Eodactylites). The Pliensbachian/ Toarcian boundary (PLB/TOA) is contained in a continuous section forming over 450m of carbonate-rich sediments. Tectonics, syn-sedimentary disturbance, metamorphism or significant diagenesis do not significantly affect this area. At the PLB/TOA, no vertical facies changes, stratigraphical gaps or hiatuses have been recorded. The base of the Toarcian Stage is marked in the bed 15e by the first occurrence of D. (E.) simplex, co-occurring with D. (E.) pseudocommune and D. (E.) polymorphum. The ammonite association of D. (Eodactylites) ssp. and other species e.g. Protogrammoceras (Paltarpites) cf. paltum, Lioceratoides aff. ballinense and Tiltoniceras aff. capillatum is particularly significant for the boundary definition and correlation with sections in different basins. Ammonites of the PLB/ TOA are taxa characteristic of both the Mediterranean and Northwest European provinces that allow reliable, global correlations. The PLB/TOA is also characterized by other biostratigraphical markers (brachiopods, calcareous nannofossils, ostracods and benthic foraminifers) and by high-resolution stable carbon and oxygen isotopes, and 87Sr/86Sr ratios that show distinctive changes just above the PLB/TOA, thus providing additional, powerful tools for global correlations. The PBL-TOA lies at the end of a second (and third) order cycle of sea-level change, and the top of bed 15e is interpreted as a sequence boundary. Cyclostratigraphy analysis is available for the Lower Toarcian of Ponta do Trovão. Detailed correlations with the Almonacid de la Cuba section (Iberian Range, Spain) provide complementary data of the ammonite succession in the Northwest European Hawskerense and Paltum Subzones, and magnetostratigraphical data that allow supraregional correlations. The proposal was voted on by the Toarcian Working Group in June, 2012, and by the International Subcommission on Jurassic Stratigraphy in September, 2012, approved by the ICS in November, 2014, and ratified by the IUGS in December, 2014. With this Toarcian GSSP, all international stages of the Lower Jurassic have been officially defined.