Geometry of a foreland basin over an inherited diffuse rift transfer zone: the western Jaca-Pamplona Basin

The geometry and evolution of foreland basins in orogenic systems that overprint earlier rifts largely depends on the distribution of rift inheritance. Particularly, the inversion of inherited rift transfer zones drives regional-scale non-cylindrical geometries which impose strong constraints on the 3D distribution of shortening, orogenic topography and syn-orogenic sedimentary depocenters and dispersal patterns. This work addresses the 3D geometrical study of the western part of the Jaca-Pamplona Basin (southern Pyrenees), which represents the early South Pyrenean foreland basin. At its western part, the foreland basin transitions and overlaps the Pamplona transfer zone, a major fringe of oblique structures that resulted from the inversion of a Cretaceous, diffuse rift transfer zone. While basement and cover geometries have been recently revisited in the central and eastern Jaca–Pamplona Basin, the western basin segment remains comparatively underexplored.

To tackle this gap in subsurface characterization, we compiled and interpreted available seismic information. Seismic profiles extend along ~ 3500 km and provide an acceptable 3D coverage of the study area. They are tied by 13 exploration wells, seven of them with associated delta time well log data. The integration of surface geology, seismic surveys and exploration wells has allowed a regional-scale characterization of basement geometries and syn-orogenic depocenters across the study area. Seismic profiles depict a basement that is involved in the deep structure of the western Jaca-Pamplona Basin. Basement units are affected by numerous thrusts that partly result from the reactivation of inherited Permian-Triassic and Early Cretaceous extensional faults. Inverted basement structures are neither cylindrical nor coaxial within the study area, resulting in oblique basement thrust ramps and an along-strike partitioning of outcropping folds and thrusts.