Three-dimensional flexural modelling of the Ebro Basin (NE Iberia)

The Ebro Basin, the southern foreland basin of the Pyrenees, has undergone a complex evolution in which, apart from the Pyrenees, the Iberian Range an d the Catalan Coastal Ranges have played an important role, both as sedimen t sources and as basin confining structures. The deflected basement underly ing the Ebro Basin dips north, suggesting a lithospheric-scale control on t he structure of this basin. This is compatible with the results of subsiden ce analyses, which show that the study area is not in a local mode of isost atic compensation. In order better to understand the mechanisms that led to the present config uration of the Ebro Basin, and particularly the relevance of the various ki nds of (un)loading (e.g. surrounding fold-and-thrust belts, basin topograph y, subsurface loads), we carried out a 3-D kinematic modelling study that a ccounts for the flexural state of the lithosphere, subjected to various loa ds applied at its lateral boundaries, and the sedimentary fill of the basin . We also included the effect of Neogene extensional tectonics along the ea stern basin margin, which is related to the opening of the Valencia Trough. We show the suitability of the 3-D lithospheric-scale flexural modelling ap proach to the study of NE Iberia. Modelling results point to a relatively s trong lithosphere in this area, with values of effective elastic thickness ranging from 10 to 35 km in the Ebro Basin, increasing towards the Pyrenees . We also find that the topographic (tectonic) load itself is insufficient to explain the observed basement deflection. Thus an extra subsurface load beneath the Pyrenees, corresponding to the underthrusted Iberian lithospher e, is required. The effect of lithospheric stretching in the Valencia Troug h on the Ebro Basin is appreciable only in its eastern part, where the lith osphere was uplifted. This had considerable repercussions on the sedimentar y and erosional regime of the Ebro Basin. We have analysed the link between the stretching-related, tectonically uplifted areas and the erosional patt erns observed onshore northeast Iberia.