Multiple mechanisms driving detachment folding as deduced from 3D reconstruction and geomechanical restoration: the Pico del Águila anticline (External Sierras, Southern Pyrenees)


Correspondence: Oskar Vidal-Royo, Geomodels Research Centre, GGAC, Departament de Geodinàmica i Geofísica, Facultat de Geologia, Universitat de Barcelona, C/Martí i Franquès s/n, 08028, Barcelona, Spain. E-mail:


Three-dimensional (3D) modelling allows observation of geological features that may not be evident by classical two-dimensional approaches. This is particularly important in the Pico del Águila anticline (Central External Sierras, Southern Pyrenees, Spain), a structure characterized by important geometrical variability in 3D. The Pico del Águila is a N–S-trending fold, transverse to the E–W-trending South-Pyrenean thrust front, with well-exposed growth strata that record the evolution of the structure and the influence of the South-Pyrenean thrust front. Fold kinematics is complex and not precisely quantified. It is characterized by multiple folding mechanisms acting simultaneously in a heterogeneous stratigraphic sequence. To better understand the fold's structural evolution, 3D reconstruction and geomechanical restoration of the structure were performed. The restoration takes into account rock mechanical properties without assuming a specific kinematic model. Our work suggests that the growth of the structure was characterized by variable uplift/sedimentation rates through time and between fold limbs. The restoration also reveals that a combination of multiple folding mechanisms operated simultaneously in different units and structural domains during anti-clinal growth. This has major implications in the understanding of detachment folds with associated growth strata, as such structures are described in many settings as potential traps for hydrocarbons and natural resources.