EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The western termination of the South Pyrenean Triangle Zone; a structural and geophysical characterization.

Pablo Santolaria1, Concepción Ayala2, Emilio L. Pueyo3,4, Félix M. Rubio5, Ruth Soto3,4, Pablo Calvín3, Aranzazu Luzón6, Adriana Rodríguez-Pintó7, Carlota Oliván7, and Antonio M. Casas-Sainz6
Pablo Santolaria et al.
  • 1University of Barcelona, GEOMODELS Research Institute, Spain (
  • 2Instituto Geológico y Minero de España, IGME, Tres Cantos, Madrid, Spain. Present address: Geosciences Barcelona, CSIC, Barcelona, Spain
  • 3Instituto Geológico y Minero de España, Unidad de Zaragoza, Zaragoza, Spain
  • 4Associated Unit in Earth Sciences IGME – Univ. Zaragoza.
  • 5Instituto Geológico y Minero de España, IGME, Tres Cantos, Madrid, Spain.
  • 6Departamento de Ciencias de la Tierra, Geotransfer Research Group, Instituto de Investigación en Ciencias Ambientales (IUCA), Universidad de Zaragoza
  • 7Freelance geologist

The presence of multiple evaporite levels strongly influence the structural style and kinematics of fold-and-thrust belts. Particularly (but not exclusively) in their fronts, it is common for these décollements to favor the formation of triangle zones. In the central portion of the Pyrenees, the South Pyrenean Triangle Zone represents the frontal part of this chain, that involves the Oligocene-Miocene Ebro Basin foreland deposits. We have focused on its western termination, characterized by a salt-cored anticline that laterally passes to a backthrust which dies out to the west. These structures are detached on the Upper Eocene-Lower Oligocene syntectonic evaporite Barbastro Formation (and lateral equivalents) that acted as a multidetachment unit. To the north, the south-directed Pyrenean thrust unit detached on Middle-Upper Triassic evaporites to finally glide along the Upper Eocene-Lower Oligocene décollement horizons.

In this contribution, we present a detailed structural and stratigraphic model of this triangle zone termination, constructed accordingly to two major approaches (1) constraining the geometry and structural architecture based on surface geology, interpretation of seismic lines (>900 km) and wells and, (2) obtaining the 3D density distribution of the detachment level (Barbastro Fm. and lateral equivalents as well as deeper, Triassic evaporites) using gravity stochastic inversion by means of more than 7000 gravity stations and 1500 actual density data from surface rocks. All in all, this multidisciplinary approach allows us to characterize the western termination of the South Pyrenean Triangle zone as the transition from a ramp-dominated and multiple triangle zone to a detachment-dominated one whose geometry, kinematics, and location were controlled by the distribution and heterogeneity of the Upper Eocene-Lower Oligocene syntectonic décollements and the southern pinch-out of the basal detachment of this unit.

How to cite: Santolaria, P., Ayala, C., Pueyo, E. L., Rubio, F. M., Soto, R., Calvín, P., Luzón, A., Rodríguez-Pintó, A., Oliván, C., and Casas-Sainz, A. M.: The western termination of the South Pyrenean Triangle Zone; a structural and geophysical characterization., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3417,, 2021.

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