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[EN] An integrated study including magnetostratigraphy, larger benthic foraminifera and calcareous nannofossil biostratigraphy is presented herein. This work was performed in shallow marine siliciclastics rich in larger foraminifera, around the Ypresian/Lutetian boundary in the Ésera valley (South-Central Pyrenees). Although the calcareous nannofossil content in the studied interval is low, not allowing a precise Y/L boundary to be recognised, the taxa found are enough to support the chronostratigraphic attribution. Data obtained in the Ésera valley section has improved the knowledge of larger benthic foraminifera (Nummulites and Assilina) distribution through chron C21. SBZ 11 to SBZ 12 transition took place at the lowermost C21r, as shown in previous works. SBZ 12 assemblages extend into C21n, where the SBZ 12 to SBZ 13 boundary occurs. These data, obtained in shallow marine siliciclastic facies, with in situ fauna, results in a shift of the SBZ 12/SBZ 13 boundary to the Lower Lutetian, younger than previously believed. Accordingly, the Ypresian/Lutetian boundary occurs in SBZ 12.

[EN] Despite the large number of magnetostratigraphic studies in the South Pyrenean Basin aiming to calibrate the basin chronostratigraphy and the biostratigraphic scales, the South Eastern Jaca Basin remains unexplored from this perspective, and its relation with the Ainsa Basin is not fully understood. In this work we contribute with new magnetostratigraphic data from the 950m thick Las Bellostas section, located in the northern hinge of the Balzes anticline. Well-proven primary signal (positive fold test and two pseudo-antiparallel polarities) supported by numerous primary data in the surroundings allow us building a reliable local polarity sequence of eight magnetozones (from R1 to N4). Additionally, seven new biostratigraphic samples (Nummulites and Assilina) in the lower part of the section (marine environment) allows tightening the section to the Geomagnetic Polarity Time Scale (GPTS) and proposing a refined age model for the southeastern Jaca Basin. The section starts in the Boltaña Fm., of Cuisian age (Shallow Benthic Zone, SBZ11), is followed by a sedimentary gap from C22n to C20n as witnessed by biostratigraphic data (SBZ11 underneath the hiatus and SBZ16 just atop). The deltaic Sobrarbe Fm can be tracked until the C19n (Late Lutetian). From this point (200m) until the top of the section (950m), at least, the entire C18n chron can be recognized within the molassic Campodarbe Fm (C18n.2n-C18n.1r and C18n.1n) (Bartonian) equivalent to the West to the prodeltaic Arguis marls Fm. The Middle Cusian (SBZ11) to Middle Lutetian (SBZ15) stratigraphic hiatus is, in part, enhanced by the structural position at the hinge of the Balzes anticline. These new chronostratigraphic constraints help refining the W-E and N-S stratigraphic relationships in the eastern Jaca Basin and in the Ainsa Basin. This section also allows us to accurately refine the kinematics of the rotational activity in the eastern External Sierras. The important difference in magnetic declination alon

Se presenta la primera descripción de las características estratigráficas y sedimentológicas de las calizas bartonienses de la Sierra de Santo Domingo (Sierras Exteriores occidentales, Zaragoza – Huesca). La unidad representa la última etapa de desarrollo de plataformas carbonatadas del Eoceno en la cuenca de Jaca tras la transgresión del Luteciense terminal, dando paso a una sedimentación deltaica. En este contexto, la fábrica de carbonatos estuvo condicionada por un nivel trófico elevado. El depósito tuvo lugar en un ambiente de rampa carbonatada, en el que se diferencian dominios de rampa interna, media y externa. La rampa interna se caracterizó por praderas de fanerógamas marinas, cuya presencia se infiere por la abundancia de foraminíferos acervulínidos con morfologías de gancho, rodofíceas geniculadas y fragmentos de equinodermos. En las facies de rampa media dominan los briozoos, bivalvos y foraminíferos como Discocyclina y Operculina. Finalmente, los pequeños foraminíferos bentónicos y planctónicos son los componentes más abundantes de la rampa externa. Estas asociaciones de carbonatos, de tipo heterozoan y con componentes fotodependientes subordinados, evidencian la influencia de la sedimentación deltaica. Por sus características estratigráficas y sedimentológicas se considera conveniente la definición de las calizas de Santo Domingo como un miembro diferenciado dentro de la Fm. Guara

Se presenta la primera descripción de las características estratigráficas y sedimentológicas de las calizas bartonienses de la Sierra de Santo Domingo (Sierras Exteriores occidentales, Zaragoza – Huesca). La unidad representa la última etapa de desarrollo de plataformas carbonatadas del Eoceno en la cuenca de Jaca tras la transgresión del Luteciense terminal, dando paso a una sedimentación deltaica. En este contexto, la fábrica de carbonatos estuvo condicionada por un nivel trófico elevado. El depósito tuvo lugar en un ambiente de rampa carbonatada, en el que se diferencian dominios de rampa interna, media y externa. La rampa interna se caracterizó por praderas de fanerógamas marinas, cuya presencia se infiere por la abundancia de foraminíferos acervulínidos con morfologías de gancho, rodofíceas geniculadas y fragmentos de equinodermos. En las facies de rampa media dominan los briozoos, bivalvos y foraminíferos como Discocyclina y Operculina. Finalmente, los pequeños foraminíferos bentónicos y planctónicos son los componentes más abundantes de la rampa externa. Estas asociaciones de carbonatos, de tipo heterozoan y con componentes fotodependientes subordinados, evidencian la influencia de la sedimentación deltaica. Por sus características estratigráficas y sedimentológicas se considera conveniente la definición de las calizas de Santo Domingo como un miembro diferenciado dentro de la Fm. Guara

The Ainsa Basin (south-central Pyrenees) is an exceptional example of a syntectonic foreland basin where structures oblique to the Pyrenean trend are well preserved. The absence of a complete chronostratigraphic frame motivated us to perform a detailed magnetostratigraphic study in the Ainsa Basin, including the shallow-marine–continental transition. Three sections covering almost the entire Eocene sedimentary fill were sampled (Ara, Coscollar, and Mondot), covering 2450 m of the sedimentary pile, with more than 1000 demagnetized specimens (sample spacing of 2.7 m). Data from previous magnetostratigraphic studies (Eripol section) allow us to complete the Eocene record with an 840-m-long profile within the Bartonian–Priabonian interval overlying the sampled sequence. Characteristic remanent magnetization (ChRM) directions were effectively isolated between 300 and 500 °C. Magnetite is the main magnetic carrier, with variable iron sulfide content and occasional hematite. Fold tests indicate a prefolding magnetization. Biostratigraphy based on shallow benthic foraminifera (15 localities) and a locality with abundant charophyte gyrogonites help to constrain the local magnetostratigraphic record (20 reversals) between the early Ilerdian and the middle Priabonian. A global correlation based on a magnetostratigraphic composite section derived from this work allows us to propose a complete chronostratigraphic frame for the Ainsa Basin infill between 55 and 45 Ma. Accumulation rates range from 2 to 53 cm/k.y., responding to retrogradational to progradational features during the early Lutetian, and a progressive increase from the middle Lutetian onward related to overall continentalization of the basin. Westward migration of subsidence is associated with progressively younger synsedimentary structures nucleating westward of the older ones in the South Pyrenean Basin

In this paper, we present a chronostratigraphic calibration of the shallow benthic zones (SBZs) of larger foraminifera during Lutetian times based on new magnetostratigraphic data (Isuela section) and two new densely sampled biostratigraphic sections (Isuela and Gabardiella). These sections are located in the External Sierras (Southern Pyrenees) and represent an ideal location to avoid previous chronostratigraphic problems. 1) They belong to a shallow carbonate shelf environment with abundant larger foraminifera, which ensure the reliability of SBZ data. 2) The time span covers almost the entire Lutetian interval. 3) The profiles are sufficiently long to establish trustworthy local scales, both the SBZs (520 m and 760 m in Isuela and Gabardiella respectively) and the paleomagnetic local polarity sequence (LPS) (520 m). 4) The excellent outcropping conditions also permit a detailed paleomagnetic and biostratigraphic sampling to be performed. The LPS at the Isuela section was built after sampling every 2.6 m. In total, more than 359 samples were thermal (244) and alternating field (115) demagnetized. Characteristic remanent magnetization (ChRM) usually dropped at 560 °C. Only 43% the samples (359 demagnetizations) gave reliable directions (high quality) for the LPS. A further short section (Gas line) was also cored (38 samples in 90 m) to obtain more detailed data for the upper part of the section. At the Isuela section, the results allow three pairs of trustable magnetozones to be assembled within the Lutetian. A further 255 samples were taken for biostratigraphic purposes, 55 sites at the Isuela and 52 at the Gabardiella sections being determinant. This density enabled a thorough study of changes in fossil associations to be performed. Assuming a constant accumulation rate within the chron boundaries, absolute ages have been estimated for the biostratigraphic boundaries. Combining all these data allows the previous calibration of SBZ during Lutetian times in the geo

[EN] The Ainsa Basin (south-central Pyrenees) is an exceptional example of a syntectonic foreland basin where structures oblique to the Pyrenean trend are well preserved. The absence of a complete chronostratigraphic frame motivated us to perform a detailed magnetostratigraphic study in the Ainsa Basin, including the shallow-marine–continental transition. Three sections covering almost the entire Eocene sedimentary fi ll were sampled (Ara, Coscollar, and Mondot ), covering 2450 m of the sedimentary pile, with more than 1000 demagnetized specimens (sample spacing of 2.7 m). Data from previous magnetostratigraphic studies (Eripol section) allow us to complete the Eocene rec ord with an 840-m-long profi le within the Bartonian–Priabonian interval overlying the sampled sequence. Characteristic remanent magnetization (ChRM) directions were effectively isolated between 300 and 500 °C. Magnetite is the main magnetic carrier, with variable iron sulfi de content and occasional hematite. Fold tests indicate a prefolding magnetization. Biostratigraphy based on shallow benthic foraminifera (15 localities) and a locality with abundant charophyte gyrogonites help to constrain the local magnetostratigraphic record (20 reversals) between the early Ilerdian and the middle Priabonian. A global correlation based on a magnetostratigraphic composite section derived from this work allows us to propose a complete chronostratigraphic frame for the Ainsa Basin infi ll between 55 and 45 Ma. Accumulation rates range from 2 to 53 cm/k.y., responding to retrogradational to progradational features during the early Lutetian, and a progressive increase from the middle Lutetian onward related to overall continentalization of the basin. Westward migration of subsidence is associated with progressively younger synsedimentary structures nucleating westward of the older ones in the South Pyrenean Basin.