The ESCI-València Trough vertical reflection experiment: a seismic image of the crust from the NE Iberian Peninsula to the Western Mediterranean

Resum

The València Trough project of the Spanish ESCI (Estudios Sísmicos Corteza Ibérica) programme focuses on deep seismic profiling at the NE Iberian margin. Up to 450 km of vertical reflection seismics have been acquired to map the present crustal structure of an area affected by successive extensional and compressional tectonics since Cenozoic times. A NW-SE crustal transect is made by a 50 km-long segment in the Iberian mainland that connects the ECORS-Pyrenees profile to the Mediterranean coast, followed by a 400 km-long line crossing the Valencia Trough and its flanks and reaching the South Balearic basin. All the new vertical reflection data have been used to obtain the crustal sections presented in this paper, after a complete reprocessing of data on academic basis to improve the resolution of some crucial areas. Beneath sedimentary sequences well differentiated in each area, the upper crust is characterised by a general absence of reflectivity along the transect, in contrast to a highly reflective, laterally varying lower crust. The Neogene extensional tectonics has not produced a significant crustal thinning in the Iberian mainland, where the Moho is found around 32 km depth. Along the flanks of the Valencia Trough the continental crust is affected by a strong thinning of 14-15 km that takes place in 50 km horizontal distance and concerns mainly the lower crust. Beneath the Balearic promontory, the reflectivity pattern suggests that compressional tectonics could have reached there deep crustal levels. High-reflective Messinian sediments and evidences of recent extensional tectonics characterise the South Balearic basin, where the crust seems to be very thin (about 6 km) and possibly of oceanic type. Further investigations by velocity-depth measurements are needed to constrain this continent-ocean transition.