The Early Cretaceous of the Iberian Basin (Northeastern Spain)

Resumo

The Iberian Basin is an extensional intracratonic basin located in the northeastern part of the Iberian Península (Figure 1). Sequence stratigraphy, subsidence analysis, and integration of basin fill data allow recognition of four successive evolutionary stages in the Iberian Basin during Mesozoic extension (Salas and Casas, 1993): (1) Triassic rift (Late Permian Hettangian);(2) Early and Middle Jurassic post-rift (Sinemurian-Oxfordian): (3) Late Jurassic-Early Cretaceousrift (Kimmeridgian-middle Albian); and (4)Late Cretaceous post-rift (late Albian-Maastrichtian).Evolution and formation of the Iberian Basin during the Mesozoic correlates well with the evolution of the North Atlantic marginal basins, the Aquitaine Basin, and the central south Pyrennean Basin (Tankard and Balkwill, 1989; Salas and Casas, 1993). The first two stages are related to the opening and spreading of the Neotethys toward the west. The third stage is related to the opening of the central Atlantic, and the fourth stage results from the opening of the Bay of Biscayaccompanied by the counterclockwise rotation of the Iberian plate and the consequent opening of the North Atlantic (Salas and Casas, 1993). During the Early Cretaceous, several isolated and well-differentiated subbasins formed in the IberianBasin. The origin of these subbasins is related to a riftingphase that took place during the Early Cretaceous concomitant with an increase in tectonic activity (Salas 257and Casas, 1993; Salas et al., 1995), creating horsts, grabens, and half-grabens controlled by listric faults(Salas, 1983); moreover, reactivation of strike-slip basement faults, inherited from the late Hercynian, seemsto have controlled Cretaceous sedimentation (Salas and Casas, 1993). Infill of these small Early Cretaceous subbasins began with continental