Analysis of the geological evolution and vertical movements in the València Trough area, western Mediterranean

Abstract

The València Trough, located between the Iberian Peninsula and the Balearic Islands, corresponds to the south-west prolongation of the Provençal Basin. The analysis of recently released seismic lines shows that the present day tectonics of the València Trough are the result of the coeval development of (1) a system of horsts and grabens in the north-west part of the basin during the Late Oligocene(?) — Early Miocene (Catalan-Valencian domain) and (2) a thrust and fold system which lasted up to the Middle Miocene and which was followed by extensional tectonics during the Late Miocene (Betic-Balearic domain). In an attempt to characterize the evolution of the València Trough, subsidence curves have been calculated for 18 wells and three regional cross-sections distributed across the basin. Backstripping of these data shows two major stages of tectonic subsidence history: (1) a first stage, coeval with basin formation (30-15 My), characterized by a rapid and strong tectonic subsidence which attains its maximum values in the central basin areas and close to the Balearic Islands; and (2) a second stage (15-0 My) in which the tectonic subsidence decreases gradually. The amount of crustal thinning estimated from a comparison of the observed and modelled tectonic subsidence ranges between 1.5 (Iberian margin areas) and 4.5 (central and south-western basin areas). These values agree with the crustal thicknesses inferred from seismic refraction data and gravimetric modelling. Nevertheless, such a degree of thinning cannot be explained by the Neogene extensional structure. The presence of thick Mesozoic deposits suggests that the present crustal thinning is partly due to previous Mesozoic extension.