Desarrollo simultáneo de pliegues, esquistosidad y cabalgamientos en el Eoceno inferior de Isaba (Valle del Roncal, Pirineo navarro)

Abstract

Geometric and kinematic analysis of Pyrenean folds, cleavage and thrusts is carried out in several exceptional outcrops of the Eocene flysch at Isaba (Navarra, Spain). Distribution, orientation and cross-cut relationships between these structures suggest that they are roughly coeval and co-genetic, the total deformation being distributed into different ductile and brittle mechanisms. The footwall of the Sierra de Arrigorrieta thrust shows a set of harmonic folds with axial-plane cleavage; an overall flattening l l = 0,7-0,85 has been estimated from their profile-section geometry. The hanging-wall shows more heterogeneous deformation: minor thrusts, complex duplexes, and non-harmonic folds with sharp changes in orientation and density of cleavage linked to thrust ramps. The structural position and the presence of some cuspatelobate folds (mullions) in turbidite levels suggest an early deformation even previous to the Larra thrust system