Evolution of a prograding shelf complex affected by salt tectonics, the case of the SW Valencia Trough

The Valencia Trough is a NE-SW trending sector of attenuated crust located between the Iberian Peninsula and the Balearic Islands in the western Mediterranean, bordered by the Catalan Coastal Ranges to the northwest, the Iberian Chain to the west, and the Balearic fold and thrust belt to the south. It includes several kilometers of Jurassic-Cretaceous rocks deposited over Upper Triassic salt associated with rifting in the western Tethyan margin. The Mesozoic deposits are deeply eroded as a result of basin inversion and uplift in Oligocene time, followed by extension in latest Oligocene-Early Miocene time. Overlying Middle-Late Miocene foreland basin sediments are associated with the subduction and rollback of the Tethyan oceanic lithosphere. During the Pliocene and Quaternary, a prograding shelf complex was established on the eastern margin of Iberia reaching 3000m in thickness and affected by extensional faulting.

The inspection of the available surface (geological maps and structural data) and subsurface data (2D seismic profiles and exploratory wells) allowed us to document the major role of the Triassic evaporitic sequence on the tectonic style and the configuration of the Pliocene to present-day sedimentary infilling in the Valencia Trough. Our results indicate that large N-S trending extensional faults, which control the depocentres of the Plio-Quaternary prograding shelf complex and offset underlying Mesozoic-Cenozoic sequence, detach into the salt layer. Supra-salt extensional deformation appears to be decoupled from extension in the sub-salt basement.

Sequential backstripping restorations also illustrate the evolution of the deformation and depositional space associated with the flexing down of diapiric structures, which are nucleated over inherited basement faults, parallel to the supra-salt ones. These diapirs were developed in the basin margin during the Mesozoic and Miocene times. The salt expulsion is mainly triggered by the overburden deposition of the prograding clinoforms wedges sourced from the rivers located to the west (e.g., Júcar, Túria and Serpis). Salt diapirs recording a Plio-Quaternary activity can be encountered in the surroundings of the basin, synchronously to the development of the withdrawal salt depocenters.

Moreover, the determination of the two extensional faults systems, salt-detached versus basement-involved, has significant implications on evaluating the structures responsible for the instrumental and historical seismicity in the area.