Geobios 43 (2010) 317–331 Original article High-resolution biostratigraphy of the Tournaisian-Visean (Carboniferous) boundary interval, Mokrá quarry, Czech Republic§ Biostratigraphie haute-résolution de la limite Tournaisien-Viséen (Carbonifère), carrière de Mokrá, République Tchèque Jirí Kalvoda a,*, François-Xavier Devuyst a,b, Ondrej Bábek a, Ladislav Dvorák a, Stepán Rak c, Jirí Rez a a Institute of Geological Sciences, Masaryk University, 2 Kotlarska, 61137 Brno, Czech Republic b Carmeuse Lime and Stone, Technology Center, 3600 Neville Road, Pittsburgh PA 15225, USA c Institute of Geology and Palaeontology, Faculty of Sciences, Charles University, 6 Albertov, Praha 2, Czech Republic Received 9 June 2009; accepted 19 October 2009 Available online 8 April 2010 Abstract This paper summarizes the results of investigations carried out in the Mokrá quarry since 2006 on the biostratigraphy of the Tournaisian-Visean (T-V) boundary interval. It also integrates previous results obtained by J. Kalvoda and collaborators. The main focus is on the boundary itself, but stratigraphically lower and higher levels have been investigated as well to provide a biostratigraphical context spanning the late Tournaisian to early Visean. This stratigraphical level has been the focus of intense international research in the recent years under the auspices of the Subcommission on Carboniferous Stratigraphy (SCCS) in order to find a new criterion and reference section (Global Stratotype Section and Point, GSSP) for the base of the Visean Stage. The appearance of Eoparastaffella simplex from its ancestor E. ‘‘ovalis’’ and the Pengchong section (Guangxi, southern China) have recently been proposed by the Task Group on the Tournaisian-Visean Boundary and ratified by the SCCS as the new biostratigraphic criterion and GSSP for the base of the Visean, respectively. The sequence exposed in Mokrá is not suitable as a GSSP, notably because it is an active quarry, but it contains most of the foraminifer and conodont guides allowing a high-resolution biostratigraphy of the boundary interval. In addition, it contains abundant trilobites. For these reasons, it constitutes one of the best sections across the T-V boundary in Europe and can serve as a useful additional reference. # 2010 Elsevier Masson SAS. All rights reserved. Keywords: Biostratigraphy; Foraminifers; Conodonts; Tournaisian; Visean; Carboniferous Résumé Cet article fait la synthèse des études biostratigraphiques menées depuis 2006 sur la limite Tournaisien-Viséen (T-V) dans la carrière de Mokrá. Les résultats obtenus précédemment par J. Kalvoda et ses collaborateurs ont été inclus. L’objet principal de l’article est la limite elle-même, mais l’intervalle stratigraphique étudié couvre le Tournaisien supérieur et le Viséen inférieur afin que la limite puisse être comprise dans son contexte. Ces dernières années, cet intervalle stratigraphique a été l’objet d’intenses recherches internationales sous les auspices de la Sous-commission de Stratigraphie du Carbonifère (SCCS) dans le but de trouver le meilleur critère biostratigraphique possible pour la base de l’étage Viséen ainsi qu’un stratotype global (Global Stratotype Section and Point, GSSP). L’apparition d’Eoparastaffella simplex dans la lignée évolutive E. « ovalis »àE. simplex et la coupe de Pengchong (Guangxi, Chine du sud) ont récemment été proposés par le Groupe de Travail sur la Limite Tournaisien-Viséen et ratifiés par la SCCS comme nouveau critère biostratigraphique et GSSP pour la base du Viséen, respectivement. La séquence stratigraphique visible à Mokrá ne remplit pas les critères d’un GSSP, notamment car il s’agit d’une carrière active, mais elle contient la plupart des espèces de foraminifères et conodontes qui permettent de définir une biostratigraphie haute-résolution de la limite Tournaisien-Viséen. La coupe de Mokrá § Corresponding editor: Frédéric Quillévéré. * Corresponding author. E-mail address: [email protected] (J. Kalvoda). 0016-6995/$ – see front matter # 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.geobios.2009.10.008 318 J. Kalvoda et al. / Geobios 43 (2010) 317–331 contient par ailleurs une riche faune de trilobites. Ces qualités en font une des meilleures coupes de la limite T-V en Europe et une coupe de référence complémentaire au stratotype. # 2010 Elsevier Masson SAS. Tous droits réservés. Mots clés : Biostratigraphie ; Foraminifères ; Conodontes ; Tournaisien ; Viséen ; Carbonifère 1. Introduction region were revised and potential new reference sections were investigated worldwide (see summary and references in Devuyst, Active research on the Tournaisian-Visean (T-V) boundary 2006). Results showed that: interval has been carried out in the past 10 years as a result of the decision of the International Commission on Stratigraphy (ICS) Eoparastaffella, used in conjunction with other foraminifer to revise and standardize the Phanerozoic chronostratigraphic and conodont taxa, allows a high-resolution biostratigraphy scale. ATask Group on the T-V boundary was set up in 1995 by in the latest Tournaisian and early Visean at the scale of the Subcommission on Carboniferous stratigraphy in order to Eurasia (Devuyst, 2006; Devuyst and Kalvoda, 2007; find a better section to replace the historical stratotype for the Devuyst and Hance in Poty et al., 2007); base of the Visean (Bastion section, Namur-Dinant Basin, The historical criterion for the base of the Visean can be southern Belgium) and to evaluate critically the applicability of retained as E. simplex is part of an evolutionary lineage the existing criterion (appearance of the foraminifer Eopar- starting in the latest Tournaisian (Hance and Muchez, 1995; astaffella simplex Vdovenko; Devuyst et al., 2003 and references Hance, 1997; Devuyst, 2006); therein). The sequence stratigraphy context (Hance et al., 2001) The Pengchong section of Guangxi, southern China, and biostratigraphy (Poty et al., 2006) of the Namur-Dinant constitutes the best-known section to replace Bastion as a Fig. 1. Satellite photograph (A) and sketch (B) showing the location of the profiles studied in Mokrá quarry (based on http://earth.google.com/). Dotted lines indicate the floors in each sub-quarry; the floors of the main quarry are numbered from B1 to B4 for reference; profiles studied are numbered from 1 to 6. J. Kalvoda et al. / Geobios 43 (2010) 317–331 319 new stratotype for the base of the Visean (Hance, 1997; Devuyst et al., 2003). Both the criterion for the base of the Visean and the new stratotype section have now been ratified by the SCCS and the International Union of Geological Sciences (IUGS; Work, 2002, 2008). Although Mokrá quarry cannot serve as a stratotype because of its sedimentary context (relatively discontinuous sedimentation), tectonic setting (see below and Dvorák et al., 1987) and because it is an active quarry, it exposes one of the best successions known for the biostrati- graphy of the T-V boundary interval with abundant and diverse foraminifers, conodonts and trilobites. Such sections are especially rare in Europe. The goal of the present work is therefore to describe the distribution of the main foraminifer and conodont guides together with trilobite occurrences in the latest Tournaisian and early Visean of Mokrá and to provide a reference T-V boundary succession in Europe. 2. Material and methods Different profiles were studied and sampled over the years, following the advance of the quarry faces. A first series of thin sections was typically made and examined to identify the richest levels. Additional numerous thin sections (over 700) were cut in the best beds. Foraminifers were studied with a high-magnification binocular microscope Nikon 80i. About 40 samples, 3 to 4 kg each, were collected, processed (standard technique with acetic acid and bromoform) and examined for conodonts in profiles 1, 2 and 3; not all were productive. Between 1500 and 2000 specimens of trilobites were collected in the late Tournaisian to early Visean part of the Brezina Fm. Two main levels were especially productive, one in the latest Tournaisian and one in the early Visean. Trilobite specimens are currently being studied by S. Rak for a Ph.D. thesis. Fig. 2. General lithostratigraphical column for the late Devonian and early Carboniferous of southern Moravia. Lithological symbols are of standard use. 3. Mokrá quarry See text for detail. 3.1. Location, general stratigraphy and sections studied located at the entrance of the eastern quarry (Fig. 1). The stratigraphically oldest profile studied (Fig. 5) exposes the Mokrá quarry is a vast active quarry composed of three sub- upper part of the Hády-Rícka Mbr (Fig. 2), characterized here quarries (Fig. 1) located 15 km east-northeast of Brno in the by medium to dark, fine-grained, sandy and cherty limestones southernmost Moravian Karst. It exposes rocks of Frasnian to overlain by dark, very sandy, medium-grained limestones and late Visean age. The Frasnian is represented by reefoid massive sandy limestone sedimentary breccias passing to the limestones (Macocha Fm) whereas the Famennian to Visean lowermost part of the Brezina Fm. The lower part of the section interval is composed of mass flow deposits, basinal shales (Hády-Rícka Lm) is not folded but becomes strongly folded in (Hády-Rícka Mbr of the Lísen, and Brezina Fms) and rarer the Brezina Fm (alternating medium- to thin-bedded bioclastic- hemipelagites (Krtiny Mbr of the Lísen Fm). The Tournaisian- lithoclastic calcarenites, bioclastic calcilutites and greenish to Visean boundary occurs in the lower part of the Brezina Fm reddish calcareous shales, locally with abundant trilobites). (Fig. 2). The middle to upper Visean is represented by typical Profile 4 (quarried out; Fig. 4) used to expose the upper part of flysch facies of the Rozstání and Myslejovice Fms (Dvorák the same massive sandy limestone breccias and the lowermost et al., 1987). part of the overlying Brezina Fm directly N-Westwards of The late Tournaisian to early Visean succession was studied Profile 3. Profile 1 (quarried out; Fig. 6) used to expose a in six main subsections referred to as ‘‘profiles’’ (Figs. 1, 3 and moderately folded (small scale) sequence in the lowermost part 4).