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Three-dimensional geologic imaging and tectonic control on stratigraphic architecture: Upper Cretaceous of the Tremp Basin (south-central Pyrenees, Spain)

¹ LMTG, Université de Toulouse-CNRS-IRD-OMP, 14 Av. Edouard Belin, 31400 Toulouse, France; bguillau{at}lmtg.obs-mip.fr
² Unité Mixte de Recherche 5212–CNRS: Modélisation et Imagerie en Geosciences–Pau (MIGP), Center Universitaire de la Recherche Scientifique-Institut Pluridisciplinaire de Recherche Appliquée (CURS-IPRA), Université de Pau et des Pays de l'Adour, Avenue de l'Université, Pau Cedex, France; damien.dhont{at}univ-pau.fr
³ LMTG, Université de Toulouse, CNRS, IRD, OMP, 14 Av. E. Belin, F-31400 Toulouse, France; brusset{at}lmtg.obs-mip.fr

Benjamin Guillaume received his M.S. degree in geology in 2005 from the University of Toulouse (France), working on the relationships between tectonics and sedimentation in the southern Pyrenees. He is currently a Ph.D. student in the geodynamics team of the LMTG at Toulouse. His research focuses on the deformation associated with the subduction of an active ridge in Patagonia.

Damien Dhont is an assistant professor of structural geology and remote sensing at the University of Pau. He received his Ph.D. in 1999 from Paris 6 University. His research interests include the structure of thrust and fold belts, the extensional collapse of orogens, and the study of the relationships between tectonics and volcanism. He now focuses on techniques aiming to a three-dimensional representation of the geology. His main studied areas are located in recent orogenic belts and plateaus of the Middle East and South America.

Stéphane Brusset is an assistant professor in basin analysis, sequence stratigraphy, and structural geology at the University of Toulouse. He received a Ph.D. from the University of Toulouse. After a short experience in oil companies, he joined the geodynamics team of the LMTG. Brusset's research interests include the structure of thrust and fold belts and relationships between tectonics and sedimentation.

In the Tremp Basin area (south Pyrenean foreland, Spain), the Campanian–Maastrichtian Orcau-Vell and Santa Engracia depositional sequences onlap the western termination of the Sant Corneli anticline. The precise mapping of the different systems tracts belonging to these depositional sequences, their spatial arrangement, and the structural control of the anticline on the sedimentation still remained unclear. To accurately interpret the geometry of the depositional sequences and to determine the factors influencing the sedimentation, we have developed a method that aims to build a three-dimensional (3-D) geological picture of this area. The originality of our approach is that the 3-D map, which consists of the volume and shape of all the systems tracts, has been produced mainly from the interpretation and combination of surface data, including a mosaic of aerial photographs at 50-cm (20-in.) pixel size and a digital elevation model at 10-m (33-ft) resolution. We have additionally constrained the model by integrating bedding dip and strike data and balanced cross sections. With respect to the 2-D, the 3-D visualization and field observations reveal the structural control at different scales of the lateral propagation of a fault-propagation fold (Sant Corneli anticline) on the stratigraphic architecture. The Orcau-Vell depositional sequence was controlled by the rise of the base level and was characterized by differences in the sedimentation rates. The emplacement of a north-south–trending gravitational normal fault, located at the western tip of the Sant Corneli anticline, was coeval with the emplacement of the Santa Engracia depositional sequence. This fault resulted from the westward propagation of the Sant Corneli anticline, generating a local slope and a depression that channeled the turbidites and the Gilbert-type delta deposits of the Santa Engracia depositional sequence. Uplift of the Sant Corneli anticline may have subsequently stopped, and the area subsided, inducing a rapid rise of the base level.