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La zona de Jánovas presenta una superposición de pliegues resultado de eventos no coaxiales. La corrección de capa de los vectores paleomagnéticos en el sistema de coordenadas original ha sido realizada de modo secuencial, siguiendo el orden inverso de los eventos de deformación, y comparada con la clásica corrección de capa. La restitución secuencial da lugar a medias mejor agrupadas, constituyendo una puerta abierta a la reconstrucción en zonas con superposición de pliegues. Por medio de las orientaciones obtenidas de la restitución secuencial, hemos determinado un modelo de edad para la zona de Jánovas, estableciéndose, una tasa de acumulación creciente, de acuerdo con la continentalización de la cuenca hacia el Bartoniense. El modelo de rotación obtenido presenta amplios errores debido a la presencia de intervalos heterogéneos de muestreo, evidenciando la necesidad de densificar el muestreo entre 50 y 45 Ma, para afinar la tendencia de rotación y principalmente entre 38 y 35 Ma donde se produciría el final de la rotación horaria del anticlinal de Boltaña, Unidad de Tres Cantos, Instituto Geológico y Minero de España, España, Unidad de Zaragoza, Instituto Geológico y Minero de España, España, Departamento de Ciencias de la Tierra, Universidad de Zaragoza, España

16 Figuras, 29 Páginas, [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 along the section and neighboring paleomagnetic data from the Balzes anticline (from ≈70º clockwise at the base of the stratigraphic section to non-significant at the top) together with the new age model for the Eastern Jaca Basin help characterizing the rotational activity of the Balzes thrust sheet. The rotation took place between chrons C20r (Middle Lutetian; 45Ma) and C17 (Lower Priabonian 37-38Ma) in agreement to nearby structures (Boltaña, Pico del Aguila anticlines) but clearly diachronic to western ones (Santo Domingo anticline). Besides, the rotational activity seems to follow a linear and continuous pattern (velocity 9-11º/Ma, R: 0.83-0.96) in contrast to closer structures that show two distinct rotational velocities (i.e. Boltaña). These new data still let open the debate on the rotational kinematics along the South Pyrenean basal thrust., This work was financed by the Sobrarbe County Research fellow-UNESCO Global Geopark (ARP) and by some projects ESS from the Spanish Science National Plan (UKRIA4D-PID2019-104693GB-I00/CTA, DR3AM. CGL2014 54118-C2-2-R and MAGIBER-II. CGL2017-90632-REDT)