Eocene-Oligocene magnetostratigraphy from the central part of the SE margin of the Ebro Basin. Magnetoestratigrafía del Eoceno-Oligoceno del sector central del margen SE de la Cuenca del Ebro. E. Costa 1, 2 , M. Gómez-Paccard 1, 2 , M. López-Blanco 1, 2 , M. Garcés 1, 2 , E. Beamud 1, 3 , J. C. Larrasoaña 4 , & L. Cabrera 1, 2 1 Grup de Geodinàmica i Anàlisis de Conques (GGAC). Universitat de Barcelona. 2 Departament d’Estratigrafia, Paleontologia i Geociències Marines, Facultat de Geologia, Universitat de Barcelona, c/ Martí i Franquès s/n 08028-Barcelona. elicosta@ub.edu , 3 Laboratori de Paleomagnetisme (Serveis de Suport a la Recerca UB-CSIC), I.C.T. “Jaume Almera”, c/ Solé i Sabarís s/n 08028-Barcelona. 4 Departament de Geologia Sedimentaria, I.C.T. “Jaume Almera”, c/ Solé i Sabarís s/n 08028-Barcelona. Abstract: Previous magnetostratigraphic studies focused in the Eocene successions of the eastern Ebro Basin have provided some absolute age for the basin infill. These results were based on some biostratigraphic constraints wich have been recently challenged. Our new results from the approximately 3000 m thick Montserrat and Maians-Rubió magnetostratigraphic sections have been integrated into the both marine and continental biochronology data, providing a more independent chronology. The resulting absolute chronology of the Montserrat-Rubió composite section represents about 10 My, covering the Lutetian to Rupelian (approximately 40.7 to 30.5 Ma). This leads to the re-evaluation of the age of the La Salut Fm. (Lutetian to Bartonian) and the Montserrat conglomerates (Bartonian to Priabonian). The last marine regression in the central part of the SE margin of the Ebro Basin yields an approximate age of about 36.0 Ma (Priabonian). Key words: Magnetostrartigraphy, Eocene, Oligocene, Ebro Basin Resumen: Estudios magnetoestratigráficos previos centrados en el Eoceno del sector oriental de la Cuenca del Ebro han proporcionado edades absolutas para el relleno sedimentario de la cuenca. Estos resultados magnetoestratigráficos están basados en anclajes bioestratigráficos que han sido cuestionados recientemente. En este trabajo se presenta el estudio magnetoestratigráfico de las secciones de Montserrat y Maians-Rubió. La sección compuesta, de unos 3000 m de potencia, se ha integrado con los nuevos datos bioestratigráficos disponibles de los registros marino y continental, obteniendo una cronología más independiente. La nueva cronología absoluta resultante representa unos 10 millones de años cubriendo desde el Luteciense al Rupeliense (aproximadamente 40.7-30.5 Ma.). Esto lleva a revisar las edades de la Formación de La Salut (Luteciense-Bartoniense) y de los conglomerados de Montserrat (Bartoniense-Priaboniense). La última regresión marina en el sector oriental de la Cuenca del Ebro se puede datar en una edad aproximada de 36.0 Ma (Priaboniense). Palabras clave: Magnetoestratigrafía, Eoceno, Oligoceno, Cuenca del Ebro INTRODUCTION The Ebro Basin (NE Iberian Peninsula) is a triangular shaped basin surrounded by three alpine ranges: the Pyrenees to the north, the Iberian Range to the SW and the Catalan Coastal Range to the SE. This basin represents the latest evolutionary stage of the South-Pyrenean Foreland Basin, which evolved from Late Cretaceous to Miocene times by flexural subsidence related to the growth of its margins because of the continental collision between the Iberian and European plates. The Ebro Basin infill includes marine and continental sediments that are Paleocene to Middle Miocene in age. Connection of the basin with the open sea was maintained until late Eocene, when ongoing convergence along the Pyrenean margin led to the final closure of its western connection with the Atlantic Ocean. Restriction of the marine conditions during the late Eocene led to the deposition of evaporites (Òdena and Cardona Formation). Since then, a long endorheic period of uninterrupted continental sedimentation led to the accumulation of a thick sequence composed by alluvial and lacustrine deposits. Previous magnetostratigraphic studies focused in the Eocene successions of the eastern Ebro Basin have already provided some absolute age constrains (Burbank et al., 1992a; Burbank et al., 1992b; López-Blanco et al., 2000; Taberner et al., 1999) for the deposition of the Eocene succession. These studies based most of their conclusions in some biostratigraphic constraints wich have been recently challenged (Cascella and Dinarès-