THE NEOGENE STRUCTURE OF THE EASTERN IBERIAN MARGIN - STRUCTURAL CONSTRAINTS ON THE CRUSTAL EVOLUTION OF THE VALENCIA TROUGH (WESTERN MEDITERRANEAN)

The presence of a thinned crust beneath the Valencia trough has been recognized for a long time. However, to date no attempt to link this thinning, inferred from geophysical data, with the superficial structures has been made. A quantification of the Neogene extensional processes in the crustal evolution of the Valencia trough is presented. As a consequence of the complexity of the Betic-Balearic domain, the analysis has been done for the Catalan-Valencian domain (northwestern areas of the trough). Crustal and superficial data in this area show that Neogene extension was accommodated by a listric normal fault system detached in a deep upper crustal level (13-15 km) in the marginal zone of the domain. Quantitative analysis of the Neogene structure shows the incoherence between the upper crustal thinning inferred from the geometric analysis of the superficial structures (beta-factor 1.4-1.5) and from geophysical data (1.8). Although the latter value agrees with that deduced from the analysis of Neogene subsidence, this incoherence suggests that the present thinned crust would be partially inherited from the Mesozoic extension. In this way, Mesozoic subsidence analysis and the recognized Mesozoic structure show that the Mesozoic extension was almost as important as the Neogene one.