3.4.4. Interplay between surface transport and vertical motions

Erosional unroofing of elevated areas causes isostatic uplift, while sedimentation in topographic lows causes flexural subsidence. Numerical modelling of the evolution of drainage networks (Garcia-Castellanos et al., 2003) shows that surface transport processes can effectively enhance tectonically induced large-scale continental topography. Despite the intrinsic non-linear nature of drainage networks, already moderate vertical movements appear to be able to organize drainage patterns in relatively flat areas where drainage is not yet well organized and incised (Garcia-Castellanos et al., 2002).

During the Late Eocene to Early Miocene compressional deformation of continental Iberia, erosion products derived from the rising structural highs were deposited in adjacent topographic lows, such as the Duero, Almazan, Ebro, Guadiana, Guadalquivir and Tagus basins. In most of these basins sedimentation persisted during the Miocene with expanding lacustrine facies (Calvo et al., 1995), but terminated at the transition to the Pliocene (Andeweg, 2002) when it gave way to erosion. This is compatible with the results of fission track studies that indicate for Central Iberia a Plio-Pleistocene phase of uplift and erosion rather than a Miocene uplift phase followed by erosion (Ter Voorde et al., 2004). The sedimentary record of the Atlantic and Mediterranean shelf basins provides information on the timing of development of the modern drainage system. For instance, development of the river Ebro, that cuts through the Catalan Coast Ranges and deeply incises into the Ebro Basin, is dated as late Tortonian by the development of its Castellon delta (Gaspar-Escribano et al., 2003). TOPO-EUROPE intends to carry out similar studies on the deltas of other major Iberian rivers, using available industrial reflection-seismic and well data, in order to constrain the timing of their activation. Moreover, the effects of erosional unroofing of continental Iberia and load-induced subsidence of it continental shelves will be modelled. These models will also be applied to the major Iberian sedimentary basins, as their tectosedimentary record permits to develop a correlation between the different deformation events and provides constraints for numerical and analogue models.