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Open Access item Biostratigraphy of the Middle Ordovician Brachiopods from Central Spain

Authors:Reyes-Abril, Jaime
Gutiérrez-Marco, J. C.
Villas, E.
Keywords:Biostratigraphy, Rhynchonelliformean brachiopods, Central Iberian Zone, Darriwilian
Issue Date:2011
Publisher:Instituto Geológico y Minero de España
Citation:Reyes-Abri, J., Gutiérrez-Marco, J.C., Villas, E. (2011). Biostratigraphy of the Middle Ordovician Brachiopods from Central Spain. En: Ordovician of the World. Instituto Geológico y Minero. p. 463-472.
Abstract:A recent taxonomic study on the rhynchonelliformean brachiopods from the Darriwilian dark shales of the Central-Iberian Zone, Central Spain (Reyes-Abril, 2009; Reyes-Abril et al., 2010) has considerably increased the number of orthides and strophomenides known across the whole Iberian Peninsula. The studied brachiopods were collected in 58 localities of 6 provinces from the regions of Castilla-La Mancha, Andalucía and Extremadura. Middle Ordovician brachiopods previously known in the area were mainly derived from upper Darriwilian rocks, while most of the new studied brachiopods are from middle Darriwilian rocks. A total of 21 genera are now known from the whole Darriwilian strata of Iberia including the strophomenide genera Aegiromena and Dactylogonia, as well as 19 orthide genera, including Almadenorthis, Gutiorthis, Orthambonites, Paralenorthis, Sivorthis, Apollonorthis, Atlantida, Brandysia, Eodalmanella, Howellites, Cacemia, Heterorthina, Tissintia, Mcewanella, Crozonorthis, Nocturnellia and Lipanorthis, plus two new genera of the families Cremnorthidae and Harknessellidae. Considering the regional biostratigraphical and biochonological context, in which the Ibero-Armorican brachiopod biozones can be easily correlated with biozones based on other fossil groups, we have followed the Mediterranean stratigraphic scale, originally proposed in Bohemia (Havlícˇek and Marek, 1973) and updated and completed in Iberia (Gutiérrez-Marco et al., 1995, 2002). Thus we are referring the stratigraphic range of the studied brachiopods to the Mediterranean regional stages Oretanian and Dobrotivian, approximately correlatable to the middle and upper stage slices (Dw2-3) of the global Darriwilian stage. Exception made with the uppermost Dobrotivian, which extends into the Upper Ordovician, correlating with the lowermost Sandbian (Gutiérrez-Marco et al., 2008; Bergström et al., 2009). Brachiopods were first used in the late nineteenth century to subdivide the Ordovician succession in Iberia (Delgado, 1897). Since then, different brachiopod biozones have been proposed for the Middle Ordovician rocks of Spain (Born, 1918; García Alcalde and Arbizu,1982; Villas, 1985; Young, 1985; Gutiérrez-Marco et al., 1984, 2002). Recent improvements in the detailed stratigraphical knowledge of many successions in the Central Iberian Zone, and on the taxonomy of important brachiopod species, have allowed the redefinition and updating of previous brachiopod biozones, which are examined in the present note.
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