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

Abstract

SUMMAR YThe Ebro Basin, the southern foreland basin of the Pyrenees, has undergone a complex evolution in which, apart from the Pyrenees, the Iberian Range and the Catalan Coastal Ranges have played an important role, both as sediment sources and as basin confining structures. The deflected basement underlying the Ebro Basin dips north, suggesting a lithospheric-scale control on the structure of this basin. This is compatible with the results of subsidence analyses, which show that the study area is not in a local mode of isostatic compensation.In order better to understand the mechanisms that led to the present configuration of the Ebro Basin, and particularly the relevance of the various kinds of (un)loading (e.g. surrounding fold-and-thrust belts, basin topography, subsurface loads), we carried out a 3-D kinematic modelling study that accounts for the flexural state of the lithosphere, subjected to various loads applied at its lateral boundaries, and the sedimentary fill of the basin. We also included the effect of Neogene extensional tectonics along the eastern basin margin, which is related to the opening of the Valencia Trough.We show the suitability of the 3-D lithospheric-scale flexural modelling approach to the study of NE Iberia. Modelling results point to a relatively strong 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 lithosphere, is required. The effect of lithospheric stretching in the Valencia Trough on the Ebro Basin is appreciable only in its eastern part, where the lithosphere was uplifted. This had considerable repercussions on the sedimentary and erosional regime of the Ebro Basin. We have analysed the link between the stretching-related, tectonically uplifted areas and the erosional patterns observed onshore northeast Iberia.

Forward modelling of the Bureba escarpment (Rioja Trough, N-Spain)

“…Those for flexure are free boundaries, meaning that no external torque is applied to the plate. The elastic thickness of 10 km is corroborated by [6,10,11]. I use erodabilities and densities from Table 2.…”

A comparison of the Iberian and Ebro Basins during the Permian and Triassic, eastern Spain: A quantitative subsidence modelling approach

“…This major rifting cycle can be subdivided into three minor syn-rift and post-rift pulses. From late Albian to late Maastrichtian time the Iberian Basin subsided during a thermal post-rift phase (Roca et al, 2001;Verges ans Garda-Senz, 2001;Salas and Casas, 1993).…”

“…Since during the Cenozoic a different tectonic pattern than rifting (basin inversion in the Iberian Basin and foreland sedimentation in the Ebro Basin) and flexural and topographical effects took place (Van Wees et al, 1996;Van Wees and Beekman, 2000;Gaspar Escribano et al, 2001); we omitted this period in our study. As Cenozoic inversion processes are not whitin the scope of this paper we will refer to the previous authors for a more detailed study of this process.…”

“…Earlier work have shown the subsidence style in the Ebro Basin Zoetemeijer et al, 1990;Gaspar-Escribano et al, 2001) and the Iberian Basin (Alvaro, 1987;Arche and L6pez-G6mez, 1999a;Salas and Casas, 1993;Van Wees and Stephenson, 1995;Van Wees et al, 1998). However, none of these studies correlated the subsidence history of both basins during the Permian and Triassic.…”

The chert from the Castelltallat Formation (south-central Pyrenees): archaeometric characterisation and archaeological implications

“…The sedimentary infill reaches a maximum thickness of 4000m and dates from the Palaeogene to the upper Miocene (e.g. Gaspar-Escribano et al 2001). The basin was filled in endorheic conditions from the Late Eocene (Costa et al 2010), which means that it was disconnected from the sea, favouring lacustrine sedimentary systems in its central sector with a low topographic gradient, with powerful and frequent expansions and retractions, particularly suitable for the formation of chert (Bustillo 2010).…”