Geologica Belgica

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Gil MACHADO, Jindrich HLADIL, Ladislav SLAVIK, Leona KOPTIKOVA, Noel MOREIRA, Madalena FONSECA & Paulo FONSECA

An Emsian-Eifelian Calciturbidite sequence and the possible correlatable pattern of the Basal Choteč event in Western Ossa-Morena Zone, Portugal (Odivelas Limestone)

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Mots-clés : sedimentology, stratigraphy, magnetic susceptibility, Emsian-Eifelian boundary, Basal Choteč Event, Odivelas Limestone, SW Ossa-Morena Zone.

Abstract

An Emsian-Eifelian carbonate-volcaniclastic sequence in south-western Ossa-Morena Zone (Portugal) was studied in terms of reef fauna, conodont biostratigraphy, macro- and micro-facies and magnetic susceptibility stratigraphy. The results point to a bracketing between the Po. patulus and T. australis conodont biozones (uppermost Emsian – middle-late Eifelian). The field data, facies analysis and reef fauna indicate that the sequence is composed entirely of calciturbidite and debris-flow deposits (intercalated with hemipelagic tuffites) related to a (up-slope) reefal system resting on top of volcanic buildings within a large volcanic complex. The purity of the limestones does not seem to be generally influenced by volcanic contributions. Although with some uncertainties, the first part of the section seems to show pre-, syn- and post-Basal Choteč Event (BCE) beds as recorded by significant shifts in lithofacies and magnetic susceptibility signal. A tentative interregional correlation with magnetic susceptibility curves is suggested with sections in Morocco, Nevada (USA) and Uzbekistan.

To cite this article

Gil MACHADO, Jindrich HLADIL, Ladislav SLAVIK, Leona KOPTIKOVA, Noel MOREIRA, Madalena FONSECA & Paulo FONSECA, «An Emsian-Eifelian Calciturbidite sequence and the possible correlatable pattern of the Basal Choteč event in Western Ossa-Morena Zone, Portugal (Odivelas Limestone)», Geologica Belgica [En ligne], volume 13 (2010), number 4 - Magnetic susceptibility, correlations and Palaeozoic environments, 431-446 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=3124.

About: Gil MACHADO

GeoBioTec, Geoscience Department, University of Aveiro, 3810-193 Aveiro, Portugal. E-mail: machadogil@gmail.com

About: Jindrich HLADIL

Institute of Geology, AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic;

About: Ladislav SLAVIK

Institute of Geology, AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic;

About: Leona KOPTIKOVA

Institute of Geology, AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic;

About: Noel MOREIRA

LIRIO - Laboratório de Investigação de Rochas Industriais e Ornamentais, Espaço Ciência, Convento das Maltezas, 7100-513 Estremoz, Portugal;

About: Madalena FONSECA

IICT - Instituto de Investigação Científica Tropical; DCN-GeoDES, Tapada da Ajuda 1349-017 Lisboa

About: Paulo FONSECA

Geology Department and CeGul, Faculty of Sciences of the University of Lisbon, Edifício C6, Campo Grande, 1749-016 Lisbon, Portugal;