Coniacian/Santonian boundary in Riu de Carreu valley and Prats de Carreu, South-Central Pyrenees (N Spain)



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Title: Coniacian/Santonian boundary in Riu de Carreu valley and Prats de Carreu, South-Central Pyrenees (N Spain)
Authors: Consorci del Museu de Ciències Naturals de Barcelona
Gallemí, Jaume
López, Gregorio
Martínez, Ricardo
Mercedes, Ramón
Pons, José María
Issue Date: Sep-2002
Keywords: Cretaci
Mol·luscs fòssils
Cefalòpodes fòssils
Spatial coverage: Pirineus
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Publisher: Subcommission on Cretaceous Stratigraphy - Santonian Working Group, IUGS (International Commission on Geological Sciences-UNESCO) - ICS (International Commission on Stratigraphy)
Extent: 1 p.
Abstract: A conspicuous level containing Platyceramus undulatoplicatus (Roemer) occurs in several stratigraphic profiles measured and sampled in a 15 km wide area along Riu de Carreu valley and Prats de Carreu. This is the index species for the Coniacian-Santonian boundary following the criterion suggested for the definition of the Coniacian-Santonian boundary by the Santonian working group (Lamolda & Hancock, 1996). Its presence, not only allows the identification in this area of the Coniacian-Santonian boundary, but also facilitates the re-examination of previous biostratigraphic framework. It becomes also evident that the presence of Platyceramus undulatoplicatus is relatively facies independent, since it occurs from the calcareous platform of the western part of the area to the talus marls of the eastern one. The area is located at the northern flank of the Sant Corneli Anticline, a southward verging South Pyrenean thrust propagation fold, and the outcrops, of well developed platform and basin facies, range from the Coniacian to the Santonian and are extremely well exposed. Stratigraphic units of the area were formally named by Gallemí et al. (1982). However, other authors have been inconsistently using informal names (Gili et al., 1996, Vicens et al., 1998). The biostratigraphic survey on these platform-basin outcrops is based mainly on inoceramids, rudists, ammonites, echinoids, brachiopods and planktonic foraminifera. Early biostratigraphic framework has been developed by Pons (1977), Martínez (1982), Gallemí et al. (1983), López (1986), Gómez-Garrido (1989), Gallemí (1994) and Muñoz (1995). Vicens et al. (1998) correlated, both stratigraphically and sequentially, the transit between basin and platform sequences in the western part of the area. High-resolution biostratigraphic framework on inoceramid-ammonite biozones is being currently developed to check accurate relationships between Platyceramus undulatoplicatus and other fossils record, especially that of Texanites species. The lowermost Santonian is precisely established by means of the very abundant and conspicuous Platyceramus undulatoplicatus (Roemer). This index inoceramid species co-occurs mainly with other bivalves, echinoids and sponges. Other inoceramid species showing divergent ribs, as Cordiceramus cordiinitialis ickernensis (Seitz), are also reported in the Lower Santonian of the studied area. Upper Coniacian inoceramids are characterised by Magadiceramus species, as Magadiceramus subquadratus subquadratus (Schlüter) and Magadiceramus soukupi (Macáck); they overlie or co-occur with Protexanites bourgeoisi (d’Orbigny), ammonite marker for the upper part of the Upper Coniacian. Rudist faunas co-occur just below the Platyceramus undulatoplicatus beds. References Gallemí, J. 1994. Los yacimientos con equínidos del Cretácico Superior del Prepirineo de la provincia de Lleida. Tesis Doctoral microfilmada. Publicacions de la Universitat Autonoma de Barcelona, 429 p. Gallemí, J., Martínez, R. & Pons, J.M. 1982. Unidades del Cretácico superior en los alrededores de Sant Corneli (Provincia de Lleida). Cuadernos de Geología Ibérica, 8: 935-948. Gallemí, J., Martínez, R. & Pons, J.M. 1983. Coniacian-Maastrichtian of the Tremp Area (South Central Pyrenees). Newsletter on Stratigraphy, 12: 1-17. Gili, E., Obrador, A., Vicens, E., Skelton, P. & López, G. 1996. Las formaciones de rudistas de la plataforma de Sant Corneli (Cretácico superior, unidad central surpirenaica). Revista Española de Paleontología, Nº extraordinario: 172-181. Gómez-Garrido, A. 1998. Bioestratigrafía (foraminíferos planctónicos) del Cretácico superior del Surpirineo Central (España). Revista Española de Micropaleontología, 21 (1): 145-178. Lamolda, M.A. & Hancock, J.M. 1996. The Santonian Stage and substages. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, 66-supp.: 95-102. López, G. 1986. Inocerámidos del Cretácico superior de los alrededores de St. Corneli (prov. de Lleida). Publicaciones de Geología. Universitat Autònoma de Barcelona, 22: 1-123. Martínez, R. 1982. Ammonoideos cretácicos del Prepirineo de la provincia de Lleida. Publicaciones de Geología. Universidad Autónoma de Barcelona, 17: 1-197. Muñoz, J. 1995. Estudio paleontológico y bioestratigráfico de los braquiópodos del Cretácico superior del Sudpirineo catalán. Tesis Doctoral microfilmada. Publicacions de la Universitat Autonoma de Barcelona, 413 p. Pons, J.M. 1977. Estudio estratigráfico y paleontológico de los yacimientos de rudístidos del Cretácico superior del Prepirineo de la provincia de Lérida. Publicaciones de Geología. Universidad Autónoma de Barcelona, 3: 1-105. Vicens, E., López, G. & Obrador, A. 1998. Facies succession, biostratigraphy and rudist faunas of Coniacian to Santonian platform deposits in the Sant Corneli anticline (southern Central Pyrenees). Geobios, M.S. n° 22.: 403-427.
Appears in Collections:Paleontologia / Comunicacions

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