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dc.contributor.authorPujalte, Victoriano
dc.contributor.authorBaceta, Juan Ignacio
dc.contributor.authorSchmitz, B.
dc.contributor.authorOrue Etxebarria, Xabier
dc.contributor.authorPayros, Aitor
dc.contributor.authorBernaola, Gilen
dc.contributor.authorApellaniz, Estíbali
dc.contributor.authorCaballero, F.
dc.contributor.authorRobador, Alejandro
dc.contributor.authorSerra Kiel, Josep
dc.contributor.authorTosquella Angrill, Josep
dc.identifier.citationPujalte, V., Baceta, J.I., Schmitz, B., Orue Etxebarria, X., Payros, A., Bernaola, G., Apellaniz, G., Caballero, F., Robador, A., Serra Kiel, J.: "Redefinition of the Ilerdian Stage (early Eocene)". Geologica Acta. Vol. 7, n. 1-2, p. 177-194 (2009). ISSN 1695-6133en_US
dc.description.abstractThe Ilerdian Stage was created by Hottinger and Schaub in 1960 to accommodate a significant phase in the evo¬lution of larger foraminifera not recorded in the northern European basins, and has since been adopted by most researchers working on shallow marine early Paleogene deposits of the Tethys domain. One of the defining cri¬teria of the stage is a major turnover of larger foraminifera, marked by the FO's of Alveolina vredenburgi (for¬merly A. cucumiformis) and Nummulites fraasi. There is now conclusive evidence that this turnover was coeval with the onset of the Carbon Isotope Excursion (CIE) and, consequently, with the Paleocene-Eocene (P-E) boundary, a temporal correspondence that reinforces the usefulness of the Ilerdian as a chronostratigraphic sub¬division of the early Eocene in a regional context. However, in addition to the paleontological criteria, the defin¬ition of the Ilerdian was also based on the designation of two reference sections in the southern Pyrenees: Tremp (stratotype) and Campo (parastratotype). In both sections, the base of the stage was placed at the lowest marine bed containing A. vredenburgi specimens. Using the CIE as a correlation tool we demonstrate that these two marine beds occur at different chronological levels, being older in Campo than in Tremp. Further, we show that both beds are in turn younger than the lowest strata with Ilerdian larger foraminifera at the deep-water Ermua section in the Basque Basin (western Pyrenees). Since the age of stage boundaries must be the same everywhere, the choice of these stratotype sections was misleading, since in practice it resulted in the Ilerdian being used as a facies term rather than as a chronostratigraphic unit. To eliminate that conflict, and yet be respectful with established tradition, we propose to redefine the Ilerdian Stage following a procedure similar to the one used by the International Commission on Stratigraphy to establish global chronostratigraphic standards, namely: by using a "silver spike" to be placed in the Tremp section at the base of the Claret Conglomerate, a widespread lithological unit that in the Tremp-Graus Basin coincides with the onset of the CIE. The redefined regional Ilerdian Stage becomes thus directly correlatable to the lower part of the global Ypresian Stage, as cur¬rently defined by the International Commission on Stratigraphy.en_US
dc.publisherConsejo Superior de Investigaciones Científicasen_US
dc.publisherUniversidad de Barcelona
dc.publisherUniversidad Autónoma de Barcelona
dc.rightsAtribución-NoComercial-SinDerivadas 3.0 España
dc.subject.otherIlerdian stageeng
dc.subject.otherSilver spikeeng
dc.subject.otherLarger foraminiferaeng
dc.subject.otherP-E boundaryeng
dc.subject.otherTremp-Graus Basineng
dc.titleRedefinition of the Ilerdian Stage (early Eocene)en_US

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